Low 5v ref

[Yukonjay]

Hey there mr fixkick

    Thanks for all the info. Couple more quick ones before I fire this pup up again. The mafs got 12v to it So it’s def bad. Ok....

1-can I wire the sensor ground straight to the battery?

2- can I run the car without the ect maf and o2sensors?... I Caint find anything wrong with any of them or the wiring. 

      Also if I can run without all the sensors in that 5v ref circuit thought I would wire the grey yellow ground separate- straight from ecu to tps to make sure it wasn’t picking any vol anywhere. That way would be eliminating anything but the tps wiring??

        Thanks for your help!!

[Yukonjay]

Uh by not running the sensors I mean I would pull their wires out of the back of the ecu

       Thanks

[fixkick]

Hey there mr fixkick

    Thanks for all the info.
Couple more quick ones before I fire this pup up again. The mafs got 12v to it So it’s def bad. Ok.... NOT TRUE at all
the MAF is a fully electronic sensor, it has a AIR FLOW SENSOR AND AND AMPLIFIER CHIP INSIDE, THAT NEEDS POWER TO RUN AND THE PIN MARKED 12VDC (10 TO 15V)  MUST HAVE POWER ON THAT PIN OR ALL MAF FAIL HERE, ZERO POWER GETS YOU ZERO OUTPUT ON PIN 2, PIN 2 IS OUTPUT, ONLY. (CENTER PIN)



1-can I wire the sensor(un-named) ground straight to the battery? THIS TOO IS WRONG, SOME SENSORS have  a special ground wire to the ECU this special ground (sense) is MONITORed
and if ground is weak the ECU compensates for that error (tiny sure  but IMPORTANT) why do you hate factory wiring or paths..



2- can I run the car without the ect maf and o2sensors?... I Caint find anything wrong with any of them or the wiring.  ( the outputs matter, first we test outputs only to begin)
there is no need to do that unless limphome and 10mpg is fun? and black spark plugs and black smoke out tail pipe.

      Also if I can run without all the sensors in that 5v ref circuit thought I would wire the grey yellow ground separate- straight from ecu to tps to make sure it wasn’t picking any vol anywhere. That way would be eliminating anything but the tps wiring?? FOR SURE, running new wires, for sure cures a bad foctory wires but must be wired the same way.
ECU to sensor. (MAF is unique ok and is wired , power and ground different from all other sensors) The  TPS just needs 4 wires working. as Suzuki made it.

no SUZUKI nor any car with bad 5vdc will run correctly, ever, lacking 5v,  the ECU goes to limphome gross then.

        Thanks for your help!!

inline answers.

you do what ever you want to do. it is your car

seen these old pig CARS 4WD, used in a forest, tree cut, and log and bucking job , used to drag hug limbs.

that are in limphome for ever,  10MPG horror fuel usage like this, and fouled spark plugs every day.

some what it to run right
others are happy if it make noise and can move say 50ft. logging.

what matters top you ive no cue.
you are welcome, but we can fix all problems that is for sure and most  have big problems., old.

[Yukonjay]

Hey there mr Fix

   Think we’ve got our wires crossed on the maf.  I do have 12v on the blue black wire to the maf. Got 7 or more at idle on the gray black wire back to ecu. 
   I jus rewired the tps and pulled the o2 ect maf wires out of the ecu harness connector. So far so good. Def does run rich but... runs... so far. Have had it go 3 weeks n then drop my 5v to the tps so we’ll see. 
   I want to prove it’s somewhere in those wires at least so I can start to narrow it down one at a tone somehow. 
  Something interesting is that it used to have a bad lag somewhere bout 3500 rpms before and now it doesn’t?  Maybe one of the either grey wire back from tps or blue white wire??  Dunno. 
   Tested these wires and sensors every which way including pulling sensor wires out of ecu connector and sensor and load testing each wire. Haven’t found anything wrong except the maf but even with those wires pulled from back of ecu still would end up dropping my ref. Sooo I got something else goin on somewhere. 
   Thought once this thing runs awhile hopefully. I’d clip my tester to each sensor wire unplugged from ecu. Drive it around for awhile and watch for something out of whack. It’s just so intermittent that seems I’d have to watch each sensor wire for a month In order to rule it out since it’s run just fine for 3 weeks n the past. Something like that. Need a way to watch each sensor and wires for awhile and rule them out. 

   Or... tell me what you think. Rerun All these sensor wires?  Guess could still be the sensors so maybe replace these too?  

  Where it’s at now if I drop my ref vol again then it must the ecu power or ground or sensor ground???

   I’d love to take each sensor and plug them back to the ecu one at a time but I don’t want to blow another ecu. 

   Thanks for your time and insight there mr

[fixkick]

Hey there mr Fix

   Think we’ve got our wires crossed on the maf.  I do have 12v on the blue black wire to the maf. '
Got 7 or more at idle on the gray black wire back to ecu. 

SO True but you are not clear at all what pins measure what.
PIN2 the output pin of the maf can never read 7vdc.   Maf connected and back probed.
MAF pin Out list: (typ. 92-95’)  USA ! models.
 1--- Blue/black ---- Main +12vdc  power
 2--- Gray/black --- MAF output signal  1 to 5v , proportional  to Air flow.   B8     YOU MUST NOT HAVE 7vdc that is a super BAD MAF.
 3--- Black ---------- Ground.

pin 2 ,keyon not strated, is 1.0–1.6 volts
pin2 , idle 800 RPM, is  1.7–2.0 volts.
Pin 2 maf gun the throttle see 3v, never ever ever see 7vdc.

 

   I jus rewired the tps and pulled the o2 ect maf wires out of the ecu harness connector.
So far so good.
Def does run rich but... runs... so far. 
That is the whole purpose of LIMPHOME mode to run but is nasty burning, as  that is far batter than being stuck in a snow bank and a 50mile walk home.


Have had it go 3 weeks n then drop my 5v to the tps so we’ll see. 
   I want to prove it’s somewhere in those wires at least so I can start to narrow it down one at a tone somehow. 
  Something interesting is that it used to have a bad lag somewhere bout 3500 rpms before and now it doesn’t?   The MAF IS BAD< or is this in forced limphome forced by you?


WHY do this, if the MAF is bad the MAF is BAD, this must be corrected first. FOR SURE. and sure there are more problems SURE But the MAF is king and bad.
why go  past any DEAD MAF, it means no sense and the ECU will fully NUTS with that crazy 7vdc output maf,  pure hopless that. fix first thing.

Maybe one of the either grey wire back from tps or blue white wire??  Dunno. 
   Tested these wires and sensors every which way including pulling sensor wires out of ecu connector and sensor and load testing each wire.
Haven’t found anything wrong except the maf but even with those wires pulled from back of ecu still would end up dropping my ref. Sooo I got something else goin on somewhere. 
   Thought once this thing runs awhile hopefully.

I’d clip my tester to each sensor wire unplugged from ecu.   (do not do that, it is useless) we test sensor outputs running only.
Drive it around for awhile and watch for something out of whack.  (a useless in LIMPHOME test.)
It’s just so intermittent that seems I’d have to watch each sensor wire for a month In order to rule it out since it’s run just fine for 3 weeks n the past.
Something like that. Need a way to watch each sensor and wires for awhile and rule them out. 

   Or... tell me what you think.
Rerun All these sensor wires?  nah.
Guess could still be the sensors so maybe replace these too?   The MAF is bad and you are ignoring it.

  Where it’s at now if I drop my ref vol again then it must the ecu power or ground or sensor ground??? NEVER  (I F ECu has open ground or power 12v the ECU goes dead) totally dead.
5vref is a power supply inside the ECU and again, only 3 causes. (if dead 5vref, the ECU is NOT dead, you have spark and fuel and for sure limphome running) but 5vdc can be dead and car runs.
1: the sensor wires are shorted. if all read correctly the are not shorted, and if were the ECU reports them)
2: ECU bad.
3: or the 5vdc ref pin  wire is shorted to ground. (or far far far worse 12v) This ECU hates this pin to short and when does, blows up the 5reg, regulator inside.


   I’d love to take each sensor and plug them back to the ecu one at a time but I don’t want to blow another ecu.   use the voltmeter to see all sensors outputs,  and monitor for DTC errors at all times, (diagnostic jumper is harmless, use it)

   Thanks for your time and insight there mr

your welcome.!!!!!!

7v is bad maf, for sure. (connected assumed)  


a secret on mAFs, the pin 2 output is a VARIABLE current only output and the 1000 resistor,inside the ECU  converts that to voltage.!!!!!
this must be under stood first. or maf testing will fail.
on 1996+ cars the SCAN too tells me gram/s MASS air flow in the screen. G/S = grams per second flow, a very very important sensor that must work correctly and 7v is NOT IT.
if you fail to keep the maf connected pin will LIE to you for sure.

proof here, bench tested.  see my bench resistor here,?   the maf can only tested on car, or like DID below.

[fixkick]

for you , test the MAF only on the car, and connected never unconnected, to ECU.
see my voltages above. in BLUE INK text. (CONNECTED)

you must learn that skill called back probing on cars EFI this old, 1996 we can cheat, not you.
OBD2 I can see all sensors live data.
not you
only hard work with meter back probing needel probes, all sensors, (outputs)

[Yukonjay]

if blue/black power is dead to maf that bad wire makes the MAF dead, it has no power and will be dead, not a  bad  mAF just lack of power,.
pin 2 is output, Mass air flow output.

  Ok mr,

  she ran GREAT sat.  Now she’s dropped the ref vol AGAIN. Totally rewired tps. Maf ect and o2 pulled from back of ecu. She’s definitely in limp home mode now. Don’t know why it ran so good sat. Didn’t seem to affect it at all that the other sensors weren’t on there but could smell that it was runn rich- lean... something. Wasn’t getting any black smoke. Ummmm.  Ref is down to .08 now.  Totally lost again....  bad ecu???   Had a rebuilt one in there ran great for couple days without the maf plugged in minus the hiccup at say 3500 rpm then it dropped the ref.
    This time..sat... it ran even better with the rewired tps...and no maf ect and 02 sensors. 
    
  Maybe this ecu is shot????  And the other rebuilt one blew because of the bad maf??

  
    Bout ready to scrap this ol girl. Tired of throwing money at it. 

   Definitely appreciate your insight.    Thanks

[Yukonjay]

Also.....

I had the ecu on the floor so I could access it for testing. Is it missing a ground by not being screwed in??

[Yukonjay]

Ok mr,

  she ran GREAT sat.  Now she’s dropped the ref vol AGAIN. Totally rewired tps. Maf ect and o2 pulled from back of ecu. She’s definitely in limp home mode now. Don’t know why it ran so good sat. Didn’t seem to affect it at all that the other sensors weren’t on there but could smell that it was runn rich- lean... something. Wasn’t getting any black smoke. Ummmm.  Ref is down to .08 now.  Totally lost again....  bad ecu???   Had a rebuilt one in there ran great for couple days without the maf plugged in minus the hiccup at say 3500 rpm then it dropped the ref.
    This time..sat... it ran even better with the rewired tps...and no maf ect and 02 sensors. 
    
  Maybe this ecu is shot????  And the other rebuilt one blew because of the bad maf??

  
    Bout ready to scrap this ol girl. Tired of throwing money at it. 

   Definitely appreciate your insight.    Thanks

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[b]Yukonjay[/b]  
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#18
02-16-2021, 05:16 AM 
Also.....

I had the ecu on the floor so I could access it for testing. Is it missing a ground by not being screwed in??

[fixkick]

Ok mr,

  she ran GREAT sat.  Now she’s dropped the ref vol AGAIN.
Totally rewired tps. Maf ect and o2 pulled from back of ecu.
She’s definitely in limp home mode now.  
Don’t know why it ran so good sat.  (just running is easy, the limp mode does that, on all cars made (1989 up EFI) that is  the purpose of LIMP to limp home with dead sensors on the car.
it has no other purpose,  15MPG in limp home will make you go broke fast. on gas costs,  it is just to get you say out of snow bank, at -10 F and not walk home and freeze to death
that IS its only purpose, (nor stall dead in front of Logging truck with bad brakes) see?


Didn’t seem to affect it at all that the other sensors weren’t on there (you do no understand what LIMP IS or DOES) but could smell that it was runn rich- lean... something.
Wasn’t getting any black smoke. Ummmm.  (well the CAT eats up  the mess glows red hot and burns up the cat) that is what it does. in limphome mode.,)

 Ref is down to .08 now.  Totally lost again....  bad ecu???  
The +5vdc refr, is just a power source and like all sources of power, even batteries, solar cells , or generators of any kind
I'd guess max load is 1amp (even less)

1. the source is bad. (ECU) (or can be intermittent all by itself )
   
2. the wires cut. from TPS to ECU will make +5 go dead at TPS, called and OPEN circuit. (called a bad connection)
   
3. the load is shorted that means in terms of cars the sensor is shorted.
   

 if the +5vREf fails at the ECU actual pin named that, then it can not be #2, see why?  



Had a rebuilt one in there ran great for couple days without the maf plugged in minus the hiccup at say 3500 rpm then it dropped the ref.
    This time..sat... it ran even better with the rewired tps...and no maf ect and 02 sensors. 
    
  Maybe this ecu is shot????  And the other rebuilt one blew because of the bad maf??  (again the MAF  does not use +5VREF, it uses 12vdc battery power,only) forget MAF.(in this context)


  
    Bout ready to scrap this ol girl. Tired of throwing money at it.  (yes old cars are for sure a huge money sink, for sure bad ECU that costs $400 for  real one from CARDON1 refurb top source)


   Definitely appreciate your insight.    Thanks

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[b]Yukonjay[/b]  
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#18
02-16-2021, 05:16 AM 
Also.....

I had the ecu on the floor so I could access it for testing. Is it missing a ground by not being screwed in??  (yes there are 2 grounds, earth(case) and 1 battery ground.)

the case ground is only for noise reduction.  ECU runs fine like that for testing, and wise to do that way.    The inputs on the ECU have noise reduction caps to earth ground case)

sure seems to me bad +5ref inside ECU,  the TPS can not  short out, (inside it is pure carbon inside on top pure ceramic base) it will not short. wires yes.
nor ECT ,IAT (super rare to short this, but wrong sensors can, here,  but some ECT are switches inside, and no good here stolen from other cars, see folks do that, and bad to the bone it is.)

most times it is BAD WIRING,  and us super common that, on cars this old, ratty nasty wiring. (and there connector pins bad)

the MAF can NOT Short out +5vREF, it can not do that,  ever , the MAF is a 12vdc powered sensor not 5v. see?

all other sensors use 5v directly or indirectly.

for sure finding bad ECU or finding any kind of INTERMITTENT short is not easy on any car for sure moving.

the +5vref is bad inside the ECU
or the loads on it are shorting to ground,  if  shorted to 12vdc that blows the ECU +Vref up to H3LL.
Many ECUs do have bad +5vREF, and is the first test done, and DTCs or Dead CEL lamp.


this PC has mode called BACKUP mode, and tons of black smoke (or cat burning up, eating all that crap)
Backup mode is like 1960s lawmower engine, no controls at all much.

the clue is CEL lamp is totally dead.
so now you know the 3 modes of ECU, Backup, Limphome and normal.

The ECU does not know why it fails only that it DOES.

good luck finding the cause or  good  used cheap ECU,. rare that. now.