Old Generation Check Engine Lamp or C.E.L.  warning  lamp
The Tracker &  Sidekick    1989-1995 only  USA -and up to 1998 in Canada. 

Some cars Vitara's (or others)  outside N.America's   ,  run ODB1 until 2001 or 2006.

See here, In the  U.S.A. 1996 and newer cars  with OBD2 . (or Canada 1998 up)

These Older 0BD1 cars use this lamp:   Jump  here now.
 (a.k.a: Service Engine Soon (SES) lamp or M.I.L. Malfunction Indicator Lamp) 

Basic Theory:  (For lamp on driving) 1989 to 1995.  You can make your own custom hacked scan tool and avoid all this.?
The Power train control module  (PCM or ECU) sees gross engine , or EFI (fuel or spark  an sensor errors) or transmission errors.

The lamp glowing,  means the ECU has discovered operational errors running the engine.
In lay terms, the engine brain is very unhappy. (it is just a small,  old , and slow microprocessor inside ECU)

Most errors are stored in the ECU memory (even key off, it remembers them , Dome fuse not blown)
It stores errors in its  memory , until you reset them or they are self corrected.
These errors are called DTC's are diagnostic Trouble Codes.
The ECU can flash the CEL lamp to tell you which errors are stored in memory.
The flash codes ended in 1996 (forever) and a scan tool is always necessary starting in 1996 or 1998 in Canada., (USA EPA OBD2 rules and invention)

A Fast click  index: 1989-95 only.
  1. All I want, is to find the location  of all DLC connector ports,so can plant my jumper, see  Jumper locations 1989-98
  2. I know how to jumper diagnostic connector pins, I just need the early DTC code lists for (89-95)
  3. What if I can not get the CEL to flash codes (89-95) that is called the NAG feature.(my name)
  4. I just need to reset my DTC errors in memory, sorry you can not reset live real errors, ever. Real is real. Live is real. (and now !)
  5. If the CEL keep flashing all the time, the jumper was left in or the 89/90 fuse called diag, is still planted.
  6. If the CEL  lamp never comes on , the LAMP is burned out, or the ECU is fried, or the  fuse is blown to ECU (engine will not run)

Preamble, and Theory of Operation:  (of the ECU) "short and sweet?"
On board Diagnostics. (by law)
OBD began by laws passed in 1988 for 1991 year the USA in Calif. ARB  and to sell cars state wide, it was best (for Suzuki) to fit all cars, the same (near).
Suzuki began early in 1989 to meet the 1991 dead line. This ran until July 1995 last  Suzuki cars made with OBD1. (USA) 
In the USA this flashing lamp code method ended in 1996, (1998 in Canada or up to 2001 or 2006 in othere countries)
Most information written on OBD, is for OBD2,  due to the custom nature of all OBD1 systems ( and vast differences from one maker to the next)
On board, Diagnostics, means the ECU monitors the system for errors full time and is on board the ECU. (It runs tests,  finds problmes and records them in memory , all on board)
Today we use a midset of,
Old OBD1 Technology works like OBD2, but has less monitors, and has no standard scan tools, but uses lamp flash codes (DTC) instead.

OBD1 has no misfire  monitors , or CAT monitors, as taught today for all OBD2 cars. (no Evap monitor none of these, but ours has 1 EGR test)
The only monitoring is "Catastrophic sensor errors?"  In many countries the EGR is missing totally (JDM  cars) or is not monitored at all. (like Canada and rest of world.)
The ECU, starting in 1991 generates all spark and fuel injection for the engine. (before 1991 , fuel only controls)
The old system is near blind to most errors,  for example it can not tell you, that fuel pressure is too low or too high. (or the engine has damage "vacuum bounce?") (not even too low car battery like we have today)
It sees just basic dead sensor detections, only. (or gross weak EGR flows)  It can not tell you an injector is dead , leaking or partially clogged, or even that it's shorted or open coil.
It can not tell you sensors are weak.  (only dead, eg: stuck high, stuck low...)
That means you must take lots of hand done measurements to find true cause of failures.

What is a monitor?, well it's just a background process running , very much like anti-virus software running on your PC today.
It's just watching for things that are dead wrong.  (like a Granny in the rear seat, hey Sonny, the rear tire and wheel just fell off car)
Think of the ECU as 3 processes: Spark generation, fuel injection and crude monitors. (with some side shows, for  EGR op.'s and EVAP  and idle controls)
The ECU can go to limphome or to backup mode, burning a ton of fuel.

end. theory:

The OBD1 CEL lamp logic. (or not) 1 step at a time. (in short, see long version below.)

If your fuses are good and the CEL doesn't glow, then  see how to   rip  the cluster out of the dash!  (and some tricks for 16v cars!)
  1. Glows key on, mean the ECU has power and thinks, that it is happy, not corrupted, or bad, or sick. If busted, the ECU will go to Backup mode, and the lamp can go dead.
  2. The lamp can burn out  the #18-GE bulb, and the most likely is the previous owner, removed the lamp. or painted it black or some other trick (black tape)
  3. If the ECU is dead or caused by backup mode, the CEL can be totally DEAD.
  4. Keyon?,and  lamp is stuck on, will not flash 12's due to (only USA Federal cars have a nag lamp , I remove all NAG switches, that I  find, forever , just pull 4 pin connector behind speedo.) 
  5. CEL now flashes 12s on demand or others.... good, progress.
  6. The CEL is stuck on running, so you insert DLC jumper, and it flashes code 51,  seems they all do.  Carbon packed up in the EGR paths. Some countries, ECU have no CODE 51 at all !
  7. The lower the DTC number the more serious.  A bad EGR #51 might only cause stalling, pinging or hard starts, but in many cases, no symptoms at all.  (depends on how it fails)
  8. Just jumper the DLC diagnostic pin, key on, see stored codes, start car, see stored and Live codes.  12s are good all others are bad.
  9. The CEL must not flash illegal codes (99?) or abort valid flashing, mid stride.  If yes, the ECU may be  bad.
  10. The CEL glowing just key on, means it thinks it's ok , in the most basic way and some basic sensors are not totally dead,  or stuck.
  11. The CEL out running means little.  The ECU has no way to report weak sensors.   Until 1996. (and is still limited, but much better)

What are the DTC Diagnostic Trouble Codes?  All you need is a  metal paper clip jumper to see them.
Do not waste your time at Autostore X, with a pre 1996 Suzuki of any kind,  they can NOT SCAN IT !  Period ! (but any one can jumper clip test it )
The C.E.L. lamp  (or M.I.L, Maintenance indicator lamp) or S.E.S service  engine soon.
Next up , DTC code tables.  1989-95 only.
 If you get DTC code  53, see this new page.
89-95 DTC page +V6 Very Old  DTC page   
The Check Engine Light OBD1 , is glowing while driving? Some times marked SES (Service Eng. Soon). 
I will call it  a "CEL" from now on.   The jumper works only, in the Suzuki world (GEO Trackers use Suzuki ECU's)
Only on Pre 96 cars, USA or pre 98 cars and Canada or any other  out of  N.America and up to 2001. (or more)
The 1 Cent  Code reader.  No plastic or painted clips work , it must conduct electricity! Only works on pre 1996 years.
Unbend the above clip and from a "U"  and insert it into the correct pins of the under hood DLC connector, seen at the link Jumper rules, below.
The DLC (Diagnostic Logic Connector) is where you insert your paper clip,  This DLC located in the engine bay, near the battery front edge.  or at 4 other  places. See next link for them ALL.
Find  PCM Diagnostic  DLC connector and what pins to JUMP  first, here  (Suzuki loved to move it around )

The CEL  DTC Flash Rules : 
OBD1 only. The Check Engine Lamp in the dash cluster.
1989-1995 USA only.  (Suzuki/Trackers only) 
The "Diagnostic Request" jumper of the DLC causes the CEL lamp to flash out a MORSE code like ( but does not follow Morse's rules) CODE.

Like USA Cowboy& Indian smoke signals too. Like Tonto did with his "Sidekick"  the Lone Ranger.... "smoke signals 101?"
Flash ,short pause, flash-flash, long pause, repeated, is a HAPPY ECU. (but it never really knows happy, ever, in truth ) 
The PCM can flash out a whole string of non 12 codes. (unplug all sensors and see just that)
The DTC errors are presented as FLASH codes.  (most cars of this Era do this and all do it differently ,it's NOT a STANDARD ! at all)

Possible responses of the CEL?:  I will call the DTC errors, just  codes.
  • Key on,  no starting the engine,  lamp must glow solid, with no Paper clip in the DLC connector.  (if not glowing , the lamp is bad (or defeated) or bad ECU or bad (fuses?)
  • Install the DLC Jumper clip, it must now flash 12s, or some other code or a chain of codes. (if the lamp is stuck solid now, the NAG is active, defeat the Mileage NAG switch.
  • No matter what?, these codes must loop and repeat endlessly. No matter how many, or if only the good code 12.  (not looping is wrong)
  • The flashes must never end early (exception, the first code may be only partially formed, but all the repeats must be fully formed codes.) If not the ECU is bad or the battery power is too low. 9V?
  • Start the engine , the codes will continue to repeat or even decrease/increase, in number of  codes, due to errors or  self correcting.
  • You can get DTC errors, just key on, cranking, or idling or driving fast/slow.  so don't be afraid to keep the jumper installed and drive, week after week ;even !   (to see intermittent errors)
  • You are now seeing stored codes and live codes, repeating, if any, or code 12; the I AM OKAY code. 12 is NORMAL.
  • Code 51 EGR can take a while to clear,  you must drive fast and with a hot engine, for it to clear automatically,  All errors can clear automatically and in real time !
  • If you desire to clear memory , do a RESET, It also resets the TCM memory, (tranny)
  • The jumper clip inserted, may not show any codes, (no flashing at all) this is bad ECU.. My bad ECU page covers all this and more.
  • The Flashing if random or odd, or not formed correctly or truncated, is the sign of a bad ECU  or power to ECU is weak. (too low voltage , 9v is too low. 12v is good.)
  • The ECU while in BACKUP mode (dead) will freeze CEL lamp,  it will not flash on demand. (ECU board inside, acid damaged?)   (the NAG switch removed works best here)
Flash pause, Flash flash long pause. repeat over and over.  is 12, and 12 means ECU thinks ALL IS WELL. OK ! in fact, no live errors or stored errors , at this moment.
Oddity #1 , that DTC 12 and 21 can only be discerned by the LONG pause at the end!    12 , long pause, repeat.
Never hot wire any ECU on any car, or risk $500 to $1500(new) blown ECU.

The ECU can also get acid damage from the leaking CAPs. 1989 to 1995 only , in the USA and Canada. Some damage from Acid is not correctable.

I see my CEL flashing out  DTC codes now , so what do they  mean?,    Click here for a table of codes:

The DTC ,Codes will flash out , in 3 different operational modes., with the DLC, or  Diagnostic Request jumper , is jumped.

  1. KEY ON.    (memory of past failure DTC) [ not started engine ]  code 12 is Okay , code.
  2. Cranking  (can show 2 special ignition fail codes)
  3. And running/or Driving.  ( shows memory of all failures, and any live current failures!)
If the  Request Diagnostics , jumper is in PLACE.

DTC = Diagnostic Trouble codes.

DTC's (all errors) can be reset , but can return if still valid ...

Example #1:

A perfectly running car CEL lamp, behaves like this:   OBD1 only.
MUST always Glow at KEY ON "no start"   IF NOT, LOOK HERE
( or ECU  is dead, or lamp is burned out or someone removed it or put tape on it to hide it.).

This glowing, not running, SIGNIFIES, that the  ECU self tests have passed !
If the CEL is on while running ,  this SIGNIFIES there are stored/live DTC's.
We then apply the  Diag/ DLC jumper , the ECU must send codes out, or the ECU is dead.
If you place a jumper at anytime key on, and you don't get code 12 or some other code(s) then the ECU is dead.  Code 12 means NORMAL, and no errors.
A Dead ECU, can in fact start and run, but are stuck in FAILSAFE mode forever. (or worse backup-mode)
There is a special chip in the ECU , just for  backup purpose, so you will almost never be stranded. (many times)

The DLC jumper can be placed , before or after , KEY ON, Cranking or Running.
ALL codes stored, in memory ( no limit on storage time) will come streaming (flashing)out. The CEL lamp flashes.
The memory can be reset by pulling the DOME fuse. 
If the ECU is sick or in FAILSAFE, the car WILL get horrible gas mileage.  15 mpg is reported.
Some cranking codes are not stored. "41.42" But are VERY important to see in real time.
This ECU only throws DTC codes for GROSS errors.  Opens and Shorts ! In most cases,  the exception is EGR tests.
All DTC fails are real. and true! Trust them,!  ( code 51 EGR can be hard to get cleared, due to its complexity.)

Case in point :, CODE 13:  Oxy or O
If  the oxygen sensor B1S1  Bank1 Sensor 1 (left side) and S1 is front, is failing with DTC code 13 stored.
Bank means exhaust manifold bank. (a bank of cylinders)
Bank 1 means left side of cylinder 1 side of a V6,  (inline engines have only bank1)  Bank 2 is right side, if engine.
Code  13 is very rare,  because it is so insensitive.  On new cars,  this is far from true. 96+
This rare code, means the Oxygen sensor is bad, or the fueling rates are way off,  the sensor is stuck at 0v or 0.9V. for too long.  That is all this means. Finding the cause,?  Get a new sensor and find out of engine is gross lean or rich, after.
If your sensor is good (and heater not burned out inside O2) then check for gross fueling issues.
Too lean or too rich,  solve that first, and the oxygen sensor will wake up.
If the exhaust is cracked, near the 0xy.sensor that sensor will slam to 0volts and freeze there.
There is no B1S2, {sensor 2}  only on USA 1996 and newer cars, for OBD2 compliance.
There are tests that can be done, one is to use a scope on the sensor, and force fueling rich or  lean.
Example.  (8v) add propane gas to any intake openings to force a lean engine richer or pull a 25inch vacuum on the fuel
pressure regulator vacuum port to force lean.  (tricks of the trade) This later trick fools the system in to thinking its on Mount Everest, and cuts fuel. (thinking as in , the Alan Turing brain )

Rare exceptions  to  DIAG jumper locations: (Pre Trackers....)
 1989:   OBD1 only.
 (  if your car was made prior to the CAMI plant starting up in Canada  3/89 Geo Trackers. 
The Trackers first started here,  in Japan actual and used a different Diag Jumper method changed in the next month. 
Japan made the first Trackers in Japan,  then CAMI Canada plant, started up. and took over full production.
But the fuse box for this 1 month , is a deviant.! 

The only good indications  are code 12.
Flash, pause, Flash, Flash, pause, repeat.  = 12

Code 12 DTC is normal .  ( there may be more codes, that flash away , one after the other like a passing train). OBD1 only.
Do not confuse code 12 with 21.  ( a cruel joke from Suzuki engineers) flash code confusion.
The Errors run in a loop, repeating over and over. same with code 12, the GOOD code. IT MUST LOOP or the ECU is SICK.

Parting comments: OBD1 only.The ECU on all 89-95 kicks fail 1 time only for bad CAP's.
If the CEL acts odd for any reason, abnormal or you blow FI , IGN coil fuses,....

You will not get fuel injection of any kind, unless you have  spark.  ( a built in safety feature) 

OFF SITE, Common DTC's are 51 for the EGR valve, or  code 13 oxygen sensor bad, 21/22  = TPS bad, or  44/45 TPS idle switch bad.

Or my list of codes:

Note very carefully code 41 and 42  can be seen , DIAG jumper in place while cranking the engine.  <<< FANCY TRICK FOR NO STARTS.
If these flash out during cranking , then you have lost spark or have a cam sensor or spark signal failure.   ( this is a very special feature in these old cars).OBD1 only
So, if your car will not start , be sure to do the DLC jumper and crank test !!!
 The ECU never lies about these.
RPM is in the neighbor hood of 300 RPM cranking, (warm day) {before the actual sustained engine run}
The ECU will cut fueling for any loss of CMP, (cam sensor) or even the hint of bad SPARK.
So, never fail to look here, if fuel does not inject. (same with Wide open throttle, the ECU cuts fuel cranking and WOT  is showing at the TPS angle)

If you need help, ask  at below link:

Post them here on the forum:

Mind set:
 DTC memory storage issues:  
This section is OBD1 only. 
This memory is NV RAM, non volatile memory, with battery back up, (yes, the cars main battery)  The ECU has no batteries inside.

Keep in mind that if you get 5 DTC errors, some can be incorrect. (air leaks can trigger EGR failure codes, on all non thermo probe type EGR valves. )
There are primary DTC's that must be addressed first.  ) ( generally low numbers , but code 53 is bad news and is primary odd duck)
If your car has been running with battery connected for 5 years CEL ON running, there may be many real DTC's stored.
Most  OBD1  DTC codes  auto clear as faults clear, but can take many trips.
The EGR fail, is  only slow to clear DTC # 51,  this will take some driving around fast and hot.  30-50 mph in some cases.

There are 3 ways to reset all ECU/PCM.

If the CEL lamp comes on, then please pull the blink codes.  ( they are very important to trouble shooting)
All DTC's are real,  if they persist after pulling the dome fuse, then they are for sure real.
The only false codes are:
  • Someone pulled sensors with the key turned on.  (stored in memory , running or not) .
  • Engine/ sensors were bad and you fixed it. Now it's repaired and the codes stored, are bogus now. ( but will auto clear soon after start ,in seconds.)
When the ECU says the TPS, or ECT , or  IAT are failing , they are ! 
These  are gross fails on all sensors.
The EGR  DTC # 51 code takes driving car fast and hot , use RESET to clear.
Other drive off DTC' ( clear while driving) codes are, 24,44,45, and 52 ( and yes 51). 

There is a secret DTC code for troubleshooting, no starts.    ( cranking and no spark or no CAM sensor pulses)
Place DTC jumper as per above, then crank the engine,  as you crank the CEL lamp may flash out a code 41 or  42 ( CMP , or CAS failure).
This code is never stored in memory , only presented while cranking. These 2  codes do not lie, the signal is dead or is dropping out 1 out of 10 times (about)

Do not confuse code 12 GOOD with code 21 .  ( note: the long and short pauses to tell the difference)   << amazing that they did this and not skip over 21. 
One more nice trick: 
You and drive for a week with the DLC Diagnostic jumper in place , to  catch intermittent failures. Code 12 flashing day in and day out. Then BINGO GOT YOU!
Do not do that trick, to the timing freeze jumper. or you will burn up a good CAT.  (OBD2 will warn you ,if you do this, but not OBD1)

Trick1: you can drive for a week with the DTC diagnostic jumper inserted,  just to catch an intermittent DTC !!!  DO IT !
The lamp will flash 12 on and on, but then one day , 1/2 way to work , BANG !  code 22.  It's real, this is a true failure. For sure. 
A DEAD ECU is one that (simplistic) that Can't glow a good CEL lamp , key on, or can't flash code 12, on demand. (or flash some other codes) no code at all is a bad sign for the ECU.

OBD FAQ page, different countries, different rules, different history etc:

A Hit list:
  1. Never ever hot wire any ECU.
  2. Never Pull battery negative lug to reset ECU, (a last resort)
  3. Never Ground ECU pins, willy nilly.  for sure grounding the +5vref pin, does blow up a nice ECU. (on the 8v, this act blows the copper traces off the ECU main board)
  4. Never Drive with the timing freeze jumper planted. (can burn up a good CAT) (in 1996+, the ECU will warn you of this act)
  5. Never fail to remove, the NAG switch before condemning any ECU, for sure, do not buy a new ECU before removing that useless NAG switch.   Please........
  6. DO drive all day with the DIAG jumper planted, to discover Intermittent bad parts.
What is HOT wiring?, this is the foolish practice, of Jumper'ing the battery terminals (any) to the ECU pins.  DO NOT do that. (any power source or ground) 
The big NO NO is hot wiring any ECU output's,  never ever, do that. Eg. injectors, VSV drivers (many) relay drivers. etc.
If you hot wire the Fuel pump relay socket and your finger slips 1/4 inch, boom, kiss off the ECU fuel relay driver, and the same  goes for the MAIN driver.BOOM you let the smoke out. sorry ! you  did.

Oxygen sensor O , Oxy,  or Lambda Sensors,  are all the same part name.   Replace the front sensor at 100,000 miles.

How to clear or RESET these ERROR's  ,  the DTC memory on all cars:
  1. All car made here , push the reset button on all 1996+ cars with the scan tool. (can be had for $5)
  2. Remove the DOME fuse (above left knee) for 1 minute and put back.  (best in all cases , with no scan tool)
  3. Remove cars main battery cable Negative lug for 10 to 15minutes. (or turn  on headlights now and shorten time to zero) Then put back the lug. See here, on why this is bad on newer cars/
Battery pulls, also clears Radio Station programming.
IF the DTC comes back now, it's REAL.  Real as Real can be.
Sorry the AUTO stores, have no  scan tools for pre 1996 Suzuki's.

I hope I saved everyone a ton of grief,  and money.  Illegitimi non carborundum
V:34 Edited: 8-30-10  &  9-1-2013  added theory,section.  1-1-2015