SMOG  CONTROLS and Test:   Suzuki Sidekick and Geo Trackers, 1989-98                          
Look here first to see if smog is an issue?:

See page 6 on the Federal document for the 1996 failing to run monitors correctly (yes, it has bugs )

First things first, nothing on this site, shows or even hints at violating the "USA clean air ACT".  (in fact , it's 100% the opposite)  (SMOG = Smoke + FOG)
I will show, comments on the worst case state California, and at least 2 great examples of a failure.
I have no smog cheats on this page.
It is against EPA regulation to tamper (or sell devices) that alter the computer controls of Stock Gasoline engines ; be it Oxygen sensor mod.'s, and tampering with any sensors or running CAT free, in any way, is illegal.    Read this 203 section  or this on CATS.
There are legal ways  to run E85 or E100 ethanol fuels. ($$$)
By the way,  the law states a stock road car  can not be modified, for off road, that means , if a shop, sees a car and the owner says, it's off road only, but car has VIN
and compliance stickers all over it , the shop can be fined big time for not correcting or even touching the car.  Read the Cats link above, to see what happens.
So, all those adds you see, that say for off road usage only, apply to true off road only cars, that is custom made and not some modified road legal car.
These comments are for modifications, that effect the smog emissions of the engine , in any why or form  (oddly, it does not cover spark plugs.....)
Engine swaps are same year  or newer,  EFI swaps of any kind , to older or newer year  cars, can be considered tampering.
$2500 per violation, and $25,000 for shops.  Some Mfg were fined $45 million for doing off road  modifications to stock road VIN cars.
Some States, have a State smog referee, that can test and recertify you car, say with a much newer engine and EFI. (Calif has such a program) 
Last are the poor folks in P.R. of California. 
They now do a visual inspection of parts missing.  (can be extensive,  and will fail you for CAI , cold air induction , modifications, or exhaust, and a huge secret list of things )
The calculations for Penalties is here; of 2009

One more illegal sold device is the OBD2 simulator, that is, any device , designed to fool the smog man, with a custom PCM or fibber box, or some device that lies to the smog man.
Having one, or selling them are big time illegal.  Be smart, DON'T DO IT!  Google those that did and the huge fines.

O , means the natural state of oxgyen,  I will call the sensors just the O. (front or rear sensors)
Oxygen, loves to mate with it self , such that, 2 atoms of oxygen, instantly mate to O.
It also loves to mate with hydrogen and make water (H
O) instantly. (due to quantivalence reasons, USA terms)

Read what happened to this guy.  Casper  so called "
O Simulators "illegal as H3LL"

EPA Oddities, I'll never understand...  The Gray Area....
Seems spark plugs are not in the EPA radar, oddly, nor trash fuel additives, both of which, can mess up the burn cycle, greatly.  (surface fire plugs and snake oil in fuel ltank ?)

Do not try to fool your smog man (or her), not only is it illegal,  (a big fine)
Fooling the smog man is notFresh fuel, Fully Hot engine and keeping like that, before the test, a new 0xygen front sensor, and a long drive and very hot CAT before the test.

Magic Computer science stuff: (FYI):
On about year 2002 and newer cars, the newer ECU/PCM have what is Called "CVN". (checks)  In 2 forms.
CVN checks for illegal ECU stored parameters  for modifications, (using classic computer CRC methods) and VIN alterations ! That's right ,the VIN is now stored in the ECU.
On newer cars ,they can tell you HACKED your ECU.
The PCM adds up it's binary ROM code "a CRC", and checks it against , the factory build.  if wrong, the ECU was hacked.

A clean engine runs longer, uses less fuel and lets us all breath better and easier.
 end fear factors.

The GASES:    The 3 big gases  (bad) are  NOX,  CO and HC.  ( in that order)!  Nitrous Oxides,  Carbon monoxide and Hydrocarbons (raw fuel/oil)

The better the motor runs ,the more CO it produces! (see gas drawing below) ,  , having  low smog, oddly makes maximum global warming  CO
Only one cure for CO are  tiny 500-1000 cc engines that  have a low CO, and light weight tiny cars. ( and will be more deadly in a crash )
Warnings: CO:
Adverse health effects expected: near ( 0.5%) at 10% fast death, and no easy recovery.  Ask a Submariner, they panic at 3%?
30-minute exposure to 5%  produces intoxication, and concentrations greater than that (7-10%) produce unconsciousness
(9%) over 5 minutes (NIOSH 1996). is lethal. (all above readings are with  full 20% oxygen in the air)
Cure?: move person, sick,  to fresh air now, and call 911.
C0 are  those bubbles, you see, as you open a can of soda pop. The same gas, that all plants exhale or in fact ,you exhale.
CO is not controlled by  any smog station  , pass or fail. not yet, not any time soon. (but it is measured) Humans Exhale about 4% CO

HC is raw unburned (or partial) fuel. HC means, HydroCarbons. "wasted fuel"
Only HC , NOX and CO are checked and ruled upon, all 3 are nasty gases. and NOX tops that list , mother earth and the Sun, will burn up emitted  HC in to CO
They will not fail you for high CO,  paradoxically , the C02 is highest when smog is lowest ,see chart below for that proof. 

Of the 2, gases CO an NOX are very bad bed fellows. They are very nasty gases.  , 20,000 folks are treated for CO effects each year, not counting the deaths.

CO "Carbon Monoxide" kills with no warning, you get light headed pass out and die in your sleep, so don't run the car in confined spaces (kills lots of boat owners every year)
CO at just 30 minutes exposure, at 0.1% causes sickness and just 0.2% death.  (and is hard to get it out of your blood ! very hard)
 (This car in limphome mode exceeds 5 (five)% CO.  it is very very deadly to humans and near impossible for you to recover)
100% oxygen (EMT's) may be given with a tight fitting mask, as soon as it is available. , if worse, In severe cases of CO poisoning, patients are given hyperbaric chamber oxygen therapy. Finding one can be a problem....when in need... To end this risk, keep a fan running in the garage.
This CO gas also kill people with in door BBQ using charcoal briquettes or wood. or running an A.C power generator in the home. (lost electrical power)

The purpose of the CAT is to eat  up (convert ) the 3 bad gases. It does very well at that job. This CAT is a TWC,  THREE WAY CATALYST.
One more fact, the stock car EGR (working perfectly) still allows huge amounts of NOX to be emitted from the exhaust ports, so the TWC (three way cat) eats all the NOX.
NOX must be controlled by 2 steps, the EGR Valve flow and the CAT actions, to pass the test.   I try hard to get the EGR paths clean, avoiding a very expensive CAT.
The HC is controlled by the EFI  Oxygen sensor, that holds the fuel mixtures the Lowest, CO level.  When all the CO is gone the CO is max. and fuel economy is max.
BTW: some old cars , there is only a CO adjuster on the car to tune the EFI , fuel mix, it has no Oxygen sensor. I've seen JDM cars like that.

This is a complex subject, but I can limit this topic ,to one page, (long)
Think of the power plant system on the car as 4 box's
1: Fuel tank  (EVAP controls) (gasoline evaporation controls,  fumes and venting controls)
2: The Engine.
3: The 3 way CAT.
4: The Atmosphere.  ( the suck side and the expel side)
If you put in brand xxxx fuel additive (only Techron is safe) you are adding PALE oil to the fuel and  #2 will not burn oil well at all.
So to pass smog have only fresh fuel in tank , Try Chevron it has Techron already, no need to guess chemistries from the additive and fuel package.
High HC means raw fuel (or partially burned) is exiting the CAT .
In all cases,  we take 2 readings for smog , one at the engine and one at the exhaust tail pipe.
My page  shows how much engine smog lands at the #4 atmosphere.
A good technician tries  to see of the engine is dirty(too dirty , that all are dirty) and or the CAT is weak.
If you have a 5 gas tester you can, in fact, do 2 fast tests and find this simple truth.
It is true, a bad running engine can be masked (hidden) with new CAT.
The HC can also be high with EVAP fail and A/T transmission Modulator valve (3sp only) leaking and the poor engine sucking in ATF fluid, (see white smoke?)

Can't win for losing?
In some states (more each year),  you can   be failed before you even get 1 sniff.
Bad gas cap, illegal wrong cap,  or the gas tank does not hold pressure, (they test that manually with a tool) A wrong cap can do this too.
Some states (Calif) now have  full engine visual inspection way before any testing is done with sniffing, or ? other big tests , looking for non original parts in the engine and EFI.
Get Failed, for dead CEL lamp. or one that is modified in ANY way.
These rules change fast today, so find a good shop (not smog shop, but a real ASE shop for help , they will find out all facts , and you decide what is best )
Keep in mind, many shops are clueless as to how to test, diagnose or repair, old Pre 96 cars with OBD1 EFI , much less, TBI injection.

HOW to pass a smog test.? 
(only Engine and CAT ) Not visual , or gas cap, or tank pressure test.
  • Clean running engine
  • A Good working cat
  • No missing or wrong illegal smog related parts.
  • In Calif , they can fail you for any fuel leaks.
  • The fuel tank must hold pressure.
  • In 1996, all or most of the OBD2 monitors must be completed.
  • 1996+ Tranny not failing and the ECU most be CEL on key-on, and off running and no DTCs stored , even the transmission.
The monitors can be tricky , my 96 , the cat monitor fails to even start up, until oxygen sensor failures are cleared, first.  (preconditioned)
In truth, the monitors are very poorly  documented by most manufactures, no mechanic knows all these hidden logic rules.
Some cars, getting the CAT and EVAP monitors to clear, takes "divine intervention" LOL!  The EVAP  monitor will be stalled until the tank drops down to 3/4 and below full.
Some states allow one monitor to be not complete and in some, the CAT can not be that one.@!

Yes, the tranny malfunction, will fail your smog test, good reason to run a 5 speed , no?)  Here are the DTCs stored,  you don't want.
DTC means Diagnostic Trouble code,  we humans call them errors.
Get a pre-inspection, on all older cars.

The dirtiest allowed car, is the  Sidekick/Tracker to an owner in Calif. ,is 91-92 where   83 ppm HC is allowed,  Newer cars must be cleaner.!
Keep in mind a perfectly running kick engine puts out 100ppm HC (at the exhaust ports), so, the CAT, then reduces this to about 10ppm. HC.
So that 83 above,  is a dead or blow/rodded out cat , or the motor is REAL filthy , way beyond what the CAT can clean. (reaction)
Watch out some states have lower this HC bar.   PPM is parts per million.
 (Some states test 1975 cars that never had any CAT ever, and fail you , even though your car is  clean as new.)
My  page can be used for  2 reasons, what to do before or what to do after you fail ?

Buzz words: (Jargon  SAE naming conventions, etc):
  • CAT ,the  infamous - Catalyst Exhaust Converter. or CATCON  or TWC , Three Way Cat..
  • O, the Oxygen Sensor .  These are the standardized SAE names.  
  • CEL ,the Check Engine Lamp.  Technicians  name MIL, or SES, Service Engine Soon.  CEL is name used in USA.  An   I/P cluster lamp. (instrument panel)

The base line OBD rules ( for you)  " the list "  all cars 89-98
Do not smog test (real) any car with the CEL glowing or worst flashing running.  The check engine light. or DEAD CEL lamp key on.

If the ECU is throwing DTC's  (storing errors)   fix those  problem first.   "thrown, means "error stored" in the ECU memory"
Do not pull the DOME fuse or pull the battery minus terminal (for 5min) until you think you have corrected the cause of thrown DTC.  This is a ECU reset !
After resetting any ECU , you most complete all monitors running.  or the smog shop may fail you just for that. Some allow 1 monitor to be NOT COMPLETE.
Drive fast at 50 +mph then coast to a stop sign.  Freeway  driving over  5  min HOT, exit lane, coast to stop.  Usually completes all monitor tests. (save EVAP)
Drive car with  about 1/2 tank fuel to get all monitors clear.
(use a 96+ scan tool to discover , but   on  any pre 96' car , the CEL out after the HOT drive and coast, proves this fact..)
On 1996 and newer cars , the slowest monitor is 30minute long  (EVAP)  then CAT and then EGR.  The newer the car , the more monitors.  I love 96 the best.
Do get a pre-inspection! (if in Calif.  this is #1)
Do get a 5 GAS check, so you see the FULL truth.

P.R  of California CARS:
In Calif . they have a visual test, so if something is missing or the car has illegal parts or modifications, you fail instantly.

"A: Motorists who believe their vehicles may not pass initial smog certification at local Smog Check stations may request that an inspection be conducted before an official smog certification test.  "  This is called a Pre-inspection.

Government  Proof of above, is  1.8.2 chapter < here.

Do not get flagged as a Gross Polluter in California !  Can set you up for every year inspections and/or  extra deep inspections.  Avoid all costs.
Calif smog laws change fast.  I have great difficulty tracking it. So please, do your own research on the specifics of the law and districts of California variances?
Some Districts, can vary. due to the Federal rule on 200,000 population limits.
  The authority in Calif., is C.A.R.B.    I'd start here, if you need a nice nap.

1995 and EARLIER:
On early cars (dumber) the CEL doesn't come on until,  some thing  is  HORRIBLY wrong, so if it is ON, than repair  the car, first.
Not getting a pre-95 car Pre inspected, is not a good idea.   they are notorious for seeming ok and  are NOT.
The Older kicks have this nasty habit of running really bad and not telling you, with the CEL glowing.
After 1995 the ECU is so smart , many states TRUST it, 100%  (THEY HAVE HARD DATA TO BACK THAT UP, TOO) {done with random tests}
The new tests can be, just a gas cap pressure test and CEL out, congrats you pass. ( I do love this idea and is why I like 96+ cars or exempt cars.)
In some states, they sniff cars, as you drive down freeway on ramps. {on the fly| (you get a letter in the mail, sorry , you failed. bla bla bla....

Clues of why car will fail before any inspection tests,  besides the CEL glowing while running? :
The poor economy (low MPG)  is 15-20.  miles per gallon,     You ignore this.   LIMP HOME rears its ugly head.
The CAT stinks. ( that smells bad)  or CAT glows red hot, or Exhaust header does the same.
Black CLOUD effect  Exhaust,  at tail pipe, all the time.  ( a new CAT can  hide lots of wasted fuel by making lots of heat, and is a waste of time in the long run...) 
The Car is Fouling spark plugs or  O sensor long ago died or is biased. 
Your exhaust manifold or header end, are cracked or the flange gasket is bad /missing/cracked or warped.  It must not be allowed to suck air !!!
Car idles poorly and or motor shakes, misfires, has lost power.

I'd take the car to an ASE certified mechanic and have him check the car out first , before going to any Calif. Smog station.  or the like? Some states copy CALIF rules, now.!
Do not expose your failing car, to the smog station in California or they my FLAG your car as a gross polluter.  Do not let that happen.  USE PRE-INSPECTION !
If you car is 1996 and newer you can scan the car, and check out if the engine is running in closed loop at idle and cruise.
I highly recommend doing that.
With a Pre Test and the 5 gas chart (below) {please note the 02 is missing do to owner not DEMANDING 5 GAS !!!}

MEAS = measured
AVE = typical car readings on other cars.
MAX = fail trip point.
Drawing #1:    In order Carbon Dioxide,  Hydrocarbons, Carbon Monoxide, and Nitrous Oxides.   C02 is not regulated.
The better the engine runs the more C
O it produces. only using smaller cars and engines, can we save the planet, (GW fears?)

A failed Car. New motor!   No Pre-CAT measured data , and non 5gas, missing 02% readings , typical of crappy smog stations.  4gas only !
The HC ( hydrocarbons , raw fuel in  simple terms ) and  is way too high, on the test.  SEE IT?  154 ! at 15 MPH !
This is a sign of a rich EFI system or a bad CAT  (can be both, and was.. both...)
Last Column is NOX. Says NO(ppm).  (the x is missing)  23-36 parts per million.   (the EGR is working perfectly )
This car has a non OEM  after market CAT.  the CAT is either bad , too big (off v8 engine) or is mounted too far down stream. {too big is too cool and fails)
If CAT is good?, then motor is pushing 500 ppm  (A new CAT can reduce HC by  about 70%  rule).  BAD EFI . New cats to way better.
Example if  motor is spewing out 200ppm HC and the new CAT reduces that 70% the net is 200-140=60  ppm  barely passing. 100 ppm is normal at exhaust ports.
So, if motor is above 200ppm the motor is not running in closed loop. Or is misfiring.
If the ASE tech had the exhaust tapping kit from any of many major suppliers, he'd have tapped the exhaust header and measured the real engine 5 Gases.
He'd then fix the dirty engine and now you'd pass. BUT?,  if is now a marginal failure? at CAT end, time for a new CAT.

Note 25 mph test speed, is a marginal pass, I think 25mph is at a point that the MAF is very accurate and the CAT gets hotter and works better.

With no PRE CAT readings, I'm only speculating. ,  Later data showed  he had a  bad CAT and a dirty motor.

Next CAR:
Same year car  1995.:
The next is a barely PASS  , the HC is way to  high,  the CAT is nearing End Of Life ?, IMO.  Or he drove in with a cold CAT.  I think motor/EFI,  is GOOD.
No   O  was measured, so we  lots of guessing , with that column empty.  nor Pre-CAT tests. 
I like to weld and extra O bung fitting to the header then sniff there. just in front of the cat.

GAS  , combustion product gases.

The below shows how the gases behave.
Use a shop that has a 5 gas Analyzer, test for the front and rear of CAT.  Then there will be no guessing.
if the front  of cat is reading over   250 ppm HC  the motor is running wrong,  not holding Stoich , normal?, would be below 100 ppm.
The 02 (oxygen levels) would show  which side of Stoich you are on. (a big troubleshooting hint that is! )  Get it !

Carefully note if engine runs to right of legal Stoich line, car gets better MPG, if on the other and it runs on the left below the engine makes more power
So forget the , but my car is running fine statement.  Only Stoich, in USA is legal. Sorry! 
Note how CO is max , on a clean engine.  at 14.7:1 AFR. Stoich.    (only at idle and light , no hills, no W.O.T cruise) at WOT, the Fuel mix goes to about 13 , the red line.
WOT is wide open throttle or any reaction to a fast right foot."aka: enrich mode"
This chart shows the inter-relationships of the exhaust gases.   Note how oxygen works, there, on the dotted,
O line. Note how it sticks low, rich ! 

All this seems complex?, but just get the engine into Stoich at the smog test, and pass.  For years, we tuned cars for the CO  edge...
At Stoich even and old slow, ratty CAT will make the smog test pass. It sure can.  and will save you lots of labor replacing exhaust parts ( that love to cascade fail, from rust)
Get a new Front 02 and win.

General Considerations:

You have 2 choices on above car.,  (besides selling the car or moving to the country side)
Replace the CAT or tune the motor or both. Tune it  and replace that front O sensor.

Think of the CAT as a big Filth Filter , because that is what it is.

A Crude decision:
Rules for DEAD CAT:    Catalyst Exhaust converter.  These numbers are TAIL PIPE, or post CAT readings.
If CO > .3%   ( I'm saying CarbonMonOxide is greater than 0.3%)
If O > .4 %  
and the
HC > 125 ppm   but less than 400 ppm , then the  CAT is bad. (parts per million, don't ask just read the report) Only a front & rear 4/5 gas reading will prove this !

Let me say, if you fail the smog test ,I would check the state of tune on the motor and first find out if the car is entering and holding Closed LOOP.

If you replaced the CAT  and the motor still fails for  SMOG  HC, or you  decide to actually tune the motor.
You should?:
Go to any good shop and ask for a 5 gas, PreCAT analyzer test  of the exhaust input to the CAT , and do so HOT .
Find out if the motor is running in closed loop  HOT.
These tests are conclusive.  The actual motors exhaust at input to CAT can never hit 200ppm HOT. A  good goal should be 100 ppm.

High NOX? then repair the EGR system, or clean it and test it.
A lean burning AFR motor will run really hot combustion gases and NOX will be high.
A bad O , MAF or low  fuel pressure are top reasons for lean mixtures, or just a clogged fuel filter.

If NOX passes easy, then the EGR is not bad ,  if EGR is working good,  then you need a new  3way CAT  or TWC  , to  repair NOX failures.
HC: too high:
You want your motor to be below 200 PPM HC. at the exhaust header before the cat. At both speeds on the Dyno loader.

This will assure tail pipe emission of HC is below 60ppm (TAIL) or less. a 70% reduction in the CAT is EPA min. spec.  90% with a new CAT.

No words can express the utility of the quote below.   "The best of the best !"  

If you live in a state that requires the usage of CALIFORNIA cars, then you need to buy a new CAT that is certified by C.A.R.B.
NY is one such state. ( and CAL) There are others.

OBD2:  1996 to 201x:

OBD2 cars need to be treated like a bad roof, on your house.
If the shingles leak. you get pending codes.  ( good scan tools all can do this check, as can good code readers)
If the leak continues, it drips through the dry wall and hits the floor,  CEL lamp starts to glow just as feet are wet.\

Ignore the pending codes and you will chase your tail and spend lots of money, doing nothing at all.
Do not get any smog tests until all MONITORS are complete.  Again, all good code readers and scan tools, can do this check.
Do not reset the DTC errors unless you are willing to run out all the monitors.
Correct all CEL DTC malfunctions on your motor.  Do not Smog check a motor if the CEL is glowing , running.  Just a wasted of time and  money.
IF the ECU says your CAT is bad, It may be, so replace it.  (or the rear oxygen sensor first). (2 new 02 sensors are cheaper , DIY)

If you have a scan tool, then by all means use it.
Check for proper close loop operation, and that the short and long term fuel trim is not skewed., off zero by more than 5%.
Make sure all sensors respond and behave, in a rational fashion.   Coolant temp under 180F?  using the scan tool. A coolant of 195F is ok, if thermostat is 195F.

If you do fail smog , you should then go to a mechanic that has 4 or 5 gas analyzer.
If it fails for NOX , then repair the EGR system.
If the test fails for HC , then you need to do a PRE-CAT HC test.
If the CAT INPUT PPM is below 200, then that cat is bad.  I demand inputs at 100ppm or better.

All good CATS can take a 200 ppm input HC and reduce this well below the minimum 70% drop required by the EPA. (this is marginal , BTW)

These logic and rules should solve, all but the most difficult of smog failures.
Try to find out data for your exact car.
one good source is

I hope I saved you money and steps in solving this difficult problem.

Easy things to do before any test:
  • Hot motor , Hot CAT, and a HOT 02 sensor (front)  ( do not stop the engine waiting for you turn in line before the test ! )
  • Fresh Gas in the tank.  ( add some Techron to fuel per bottle instructions on full tank)  No other additive allowed, or wanted !
  • Run maximum side wall pressure in the tires, that are the driven wheels (FWD or RWD  as appropriate)  ( reset tire pressures (to OEM spec) after the test, for safety)
  • Get a tune up, and ask the mechanic to make sure car holds CLOSED LOOP HOT. If that scares him , find a real mechanic.  at 15mp and 25mph and at idle. (1)
  • Pop in a fresh new O  FRONT sensor only , into the car. A $50 part. ($20 from Delphi on Ebay)
  • New 195 deg F thermostat, HOT ,get motor HOT and it burns the fuel instead of wasting it.
  • Drive off a fast freeway or turnpike after 10 miles or more and exit and hit the smog station, if you must wait, then wait racing motor at 1500-2000 rpm.
  • Keep the CAT-CON as hot as you can !   
  • Clean the MAF before going in to station,  with MAF cleaner (All USA 16v Kicks are hot wire MAF's.)
  • If your car is OBD2 , then it has already passed the smog test already (in truth) or is in the shop getting the CEL light back off (repairs). 
  • In P.R. of California , the CEL being off , cuts you no slack .  (in most States, the CEL off ,gets the car passed, Federal rules allow that,but not in CALIF. )
  • Make sure the EVAP canister is not full of raw gasoline. 
  • No disconnected EFI or Smog parts.  Take a look for things missing or disconnected all over the engine.  Many states do physically inspection or randomly now.
Sneaky tricks:
  • 98 and older retard timing by no more than 2 degrees, may help NOX.  but my cause HC to rise , don't do it , if HC is near to limit.
  • 95 and older, block the EVAP vacuum hose to VSV.  cutting excess fuel to engine. (just for the test)
  • Do not patronize any smog or smog only test station, that can't report 5 gas , readings,like the smog report above..  You need this data, if you fail.
  • Test the EGR circuits before going in.  Do the Live test ! and the Stall test.
  • Drive above 50mph hot for 5 minutes, then cut the throttle and coast to a stop at a free way offramp.  This completes most monitors.!

Facts of life:
  • A bad motor or sick EFI , will be hidden by the very good CAT-CON.  But  soon the  new CAT-CON will go bad (runs too hot).
  • Tune up + New front O, fix exhaust leaks, + a new CAT  , and this may  get you through the test.  PASSING !
Custom cars?:   (forget down grades, going to Carb? with EFI , no way)
In Calif. that is hard. (and has special rules, I will not go in to here.)
But I can say these facts, on these cars.  ( I've helped a few guys do this)  A 96 engine in 89 Sidekick?  (yes, upgrading is legal if you follow the rules)
  • Hot motor  195F Thermostat
  • Runs in closed loop idle and cruise.
  • CAT as far forward as you can get it (custom exhaust. for sure).
  • Run  a heated front oxygen sensors. (up grade it)
  • The EGR must work and flow at max. (when commanded to do so)
and pass.

Here is a stock 90 passing  ( engine had huge vacuum leaks, found them all ., fixed  them.
Notice that 90' don't need a NOX test!  No three way cat in 90 , is my guess! for skip,  NICE !  and  uses RPM instead of speeds  !

The old ball and chain:
The 3 key factors to pass the test.  (on the loaded roller and sniff test)  ( assumes motor is not blown, or EFI gross malfunctions)

Motor fully hot, drive 25 miles then go to station and race motor at 2000 rpm waiting or get an appointment, as some allow , so you can time your arrival.
Get the CAT fully hot and keep it hot, before the tests. (on 1996 and newer cars make sure the oxygen sensor heater works (front)
In 1989/90 years there is no O heater,(1)   ( adding a heated O to early cars, maybe? illegal, but as you can see, it will help at 15mph)
The Spec.'s and tests, for Calif, are near worst case.
But, the Sidekick is a light truck LTD1 and has looser specs. ( can be more dirty , legally)   68 against 59ppm on passenger car 1995  
Here they are:
ASM5015 is 15mph and ASM2525 is 25mph readings.  Ignore the gross polluter side,  never expose your gross polluter car to any Calif . live smog stating, fix car first.

SPEC's:   (specifications and limits)
The so called CUT POINTS   (pass fail limits to a technician,  are here)  

This  next list (link to PDF) shows the 1995 cars having  16ppm HC on over 1million cars.  (this is the sign of good running motor and good CAT)
The CAT will eat 70% HC (some new ones can get 90%)  of the HC.  The CAT can in fact hide a dirty engine.

Here is the data and averages for HC  CO and NOX on millions of cars and for sure on 1995.

To get the max life out of the CAT,  keep the engine tuned and at STOICH.

Causes of high HC?
Never did the 60,000 mile tune up the cars operator guide? really?
Clogged air cleaner?, see above line, same with fuel filter.
Gasoline? liquid and raw in the engine sump oil?  change it. see above tune up.  (yes, leaking injectors do that)

  1. Bad fuel and or  do not use additives, try a tank full of CHEVRON fuel, The Techron benzene cleans injectors, very well.
  2. EFI running way rich for huge list of reasons. (bad inputs or bad actuators)
  3. Leaking or stuck or clogged injectors (the ECU does the wrong thing when this happens it goes VERY RICH) (due to misfire reason)
  4. Exhaust cracks any where near the front   O sensor, or a bad O sensor or the heater is dead in same.  (pull the exhaust manifold shield top and see #4 tube cracked?)
  5.  ECU in limphome see #2
  6. Misfiring for any reason. (cause high  O and the sensors sees this High 02 and the ECU slams rich ) can go 80% rich pre 96 or 20% rich after 95.
  7. A Bad CAT. or all any or all on this list.
  8. EVAP tank full of liquid gasoline (EVAP system failure
  9. Fuel pump running 60psi  at the fuel rail.  Fuel pressure Regulator bad.? or ?  30 is normal.
  10. Flooding
Keep in mind a clogged injectors, sends air slugs (atomospheric 20% oxygen) every exhaust stroke , down stream.
AND ? the leaking injectors causes gross misfire, and guess, what? the same deal,  more slugs of oxygen. (both are hopeless, events, to reaching STOICH)

Parting SHOT:  (EFI is not the smartest, egg in the crate) It can and will do crazy things. (lacks sensor redundancies)
Keep in mind, every MISFIRE, sends a SLUG of 20% (up to) Oxygen out the exhaust port. (our air has  about 20% oxy)
Fact 2. the O sensor output rails super lean  at with only 1% oxygen (about)  Imagine for a moment RICH MISFIRE. and the slugs of air.
Think about what the ECU does next? (it sees full lean ,so ECU injects,( goes) fuel rich and tries to hunt it to Stoich. It may fail the hunt and stick full rich.)
The ECU must hunt because the oxygen sensor shows the same reading rich and Stoich (near)
The oxygen sensor is really a switch, not a true sensor, it shows, only above or below Stoich ,so to be used, correctly it must be hunted.
The proof if that is in this chart. Toyota has the best books on this, IMO,  it states, the ECM can not tell how lean or rich it is,  the ECU must swing it, to find out where STOICH is!
Think of it this way , the ECU and oxygen sensor work together to form a united, vitual  Stoich sensor.  (what horrid, side effects). So, no swing, is no joy.
The ECU has this weakness , it can only see ? OXYGEN, from the O sensor,  and can NEVER measure fuel mixtures directly , ever...
So if the
O lies (or receives misfire air slugs, or the exhaust manifold is cracked sucking AIR) then the ECU goes super rich.  It adds FUEL to excess FUEL !
Like a boxer slugging, his own face or leaning in to a left hook !, a profound weakness.
The ECU may not be able to cure misfire (bad spark parts) and tries hard, over and over, by adjusting  the fuel mix.  Most times, if this fails, the engine is stuck rich AFR.
The Oxy
O sensor really does not measure AFR, or even direct Oxygen.
"The sensor does not directly actually measure oxygen concentration, but rather the difference between the amount of oxygen in the exhaust gas flows and the amount of oxygen in the outdoor air.
Yes, it has 2 inputs, one the exhaust and the second is ambient air flowing under the car.  (it has 2 ports) and is Differential.
This find point is only important to know, some sensors have side vents that can very easily clog with mud or grease/oil.   (yes, keep the outside clean)
Some sensors the fresh air vents are in the wire ports (tricky ,huh?)
OUTPUT Voltage.
0 volts is lean, (lots of oxygen) and 1v is rich , very little oxygen in the exhaust stream.

High measured oxygen, results in added fuel. (some call this fuel demand, sure)
Low  OXYgen, results in subtracted fuel.  (if it all works perfectly  , you hit STOICH) (the signal there swings, this is the ECU hunting prefect Stoich ) If it don't hunt, you are not in closed loop.
Older front
Misfire, oddly  ADDS fuel and you fail HC tests.   (sadly, 95 older SideKicks can add vast volumes of fuel way beyond and 96 OBD2 car) maybe 2 times more.
The 96+ year cars limit rich to 43% max.(above Stoich,  unlike the older cars.)
The system does work well , despite its weaknesses'

Great Links:   Some Really good pages.

A super Chevy Camaro post  on topic !

The Best article by Toyota , on this topic.

Parting shot: the Canada cars do not glow the CEL for all DTC errors, Ignore  this lamp if out, up there. and OBD2 did not happen in Canada until 1998. (if you see it is OBD2 it's a USA car.( really)

Additives: try Chevron Techron only if you must. 
Avoid any PRODUCT ( no names) with a guarantee to pass smog.  Please..don't suck in to lies...
Never use any additive that is listed in the MSDS as oil. (Pale oil or the like), just don't

rev. 10   4-26-2011 ,  more passing chits.  more minor edits 6-1.2013  (added links to EPA 203(a) regs. (tampering)