Low 5v ref - Printable Version

Low 5v ref - Printable Version

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Low 5v ref - Yukonjay - 01-30-2021

91 sidekick. Mpi 4dr 4x4 1.6

New here. Need help! Super stuck. Been a tryn figure this out goin on 2yrs now. Dropped the 5v ref on my tps. Grey red. Can’t find any wiring issues at all. Load tested. Tested for stray vol so on. Must have missed something but no idea what. Did find the maf was sending 7.6 back on the sensor wire. But unplugged it and still lost my ref. Falls to about 2.5ish. Then takes a week or two if I’m lucky for it too come back?‍♂️ And that’s completely unhooked from the harness testing it off gator clips to battery. Did just see that if I only put power to the ecu I would get 12+ v on my grey red wire. Even on an older computer that’s shot. It won’t go higher that .08v.

RE: Low 5v ref - fixkick - 01-30-2021

(01-30-2021, 03:00 PM)Yukonjay Wrote: 91 sidekick. Mpi 4dr 4x4 1.6 (what transmission?) stick our auto?

( i bet the VIN shows 92) code "N" is 92. VIN : S3 T D 2 1 C ? N 4 100001 (M=91)

New here. Need help! Super stuck. Been a trying to figure this out going on 2yrs now.

Dropped the 5v ref on my tps. (means 5v does not reach TPS or 5vdc is dead)

Grey red.
Can’t find any wiring issues at all.
Load tested. (not a good idea to do that, this power is weak and easy to damage ECU)

Tested for stray vol so on.
Must have missed something but no idea what.
Did find the maf was sending 7.6 back on the sensor wire. (never good that, 0 to 4v is par) never 7v, is this sinking crap China MAF> that love to do that?
the may must be marked with 58B00 on this side. or is fake MAF sold everywhere now.
But unplugged it and still lost my ref.
Falls to about 2.5ish.
Then takes a week or two if I’m lucky for it too come back?‍♂️
And that’s completely unhooked (whole ECU)?from the harness testing it off gator clips to battery.

Did just see that if I only put power to the ecu I would get 12+ v on my grey red wire. (bad ECU this is) that means the 5vdc reg is burned up to HELL

Even on an older computer that’s shot. It won’t go higher that .08v. (well bad ECU are bad, means nothing)
16 valve engine and ECu.

never seen any 91 ever with 16valves, they started in 1992. so you year told is wrong.
USA answer.
I'm sure this is 92+ car. you said MAF and first MAF ever is 1992. (USA) the MAF tells me 16valver for sure.

this is a very simple problem dead +5vdc- reference
it is just a power supply regulator deep inside the ecu, to run sensors.
dead 5v is , pin B4 is dead. not 4.75 to 5.25vdc, remover all sensors to prove ECU is bad first)
All causes here.
1: bad wiring shorted. (or open,cut or wires) to ECU B4 or any sensor. shorting.
2: shorted sensor that use 5v. (TPS, ECT. IAT (air temp if present), O2 sensor or if 02 sensor has a relay remove it)
3: A bad ECU.

to diagnose any 5vdc refr, failure, of any kind remove (unplug) all sensor on the engine, even 02. see my schematic and look carefully.

+5vdcRef fails and blows out (ECU)( for shorted sensor or some 1960s mechanic that loves to hot wire things and blows things up.
ECU pin B6

you said MAF so here they are.
all parts the run this EFI.

remove MAF, O2, ECT and if found IAT (air temp sensor) do not skip the calif ,B17 EGR sensor unplug it. if missing and wires to it are shorted , NO GOOD that.

Bench tested, A12/13 at 12v and B1/B2 at ground pin B6 must be 5vdc ( +/- 0.25v variance) if test fails the ECU is in fact BAD. (Regs inside burned up)
I bet this car shows huge DTC errors not code 12 flashing on demand, (DLC diag jumper in place)
Key on (only) the CEL must glow or ECU has no power. (CEL bulb not missing bad or black tapped out as bad boys do)

[Image: 92-95mpi-eng-full-size-huge.png]

[Image: 92-95mpi-eng-full-size-huge.png]

someone Blew up to H3LL IC117 (I made this drawing , not seen anywhere else on earth)

RE: Low 5v ref - fixkick - 01-30-2021

CHINA CRAP CLONED MAF'S SUCK,

try to find tag on MAF that shows this 58B00 ( I ask this because clones do not have this number)
USA pn. 1992 to 98
13800-58B00

real, below not FAKE. (fake EBAY , fake Amazon) real are sold at ROCKAUTO.com or from susuzki at $1300 each,so skip SUZ. This reality here, is a huge pain in the ass.
the fake ones blow up the regulator inside the MAF (crap) and blast illegal 12vdc into a once good ECU and boom.

[Image: 488_maf-real-58b00.jpeg]

RE: Low 5v ref - fixkick - 01-31-2021

the 4 wire power only bench test of the ECU , is conclusive.
5vdc dead ECU is dead.
ic17 bad, nobody on earth sells this, so super hard to repair, when blown, or pin 1 is dead IC 17, means IC7 is bad.

if the Cel lamp is dead (will not flash DTC codes at all, IC7 or Q105 are bad.
that is far as I can peel this onion, lacking more tests.

RE: Low 5v ref - fixkick - 01-31-2021

on one ECU I repaired
someone hotwired the ECU sensors.
and D107 zener turned full on, and blew the copper traces from B5 outward (D107 is sacrificial device, or for handling huge noise glitches, it is a protective device. here. and can blow to hell.)

a new diode and jumper wire over the burned to hell trace the Ecu RUNS AGAIN.

IF 5V FAILS ON ANY ECU LOOK AT THE COPPER PCB TRACE ON B5 TO SEE BURNS. ( super common this)

do not use china knock off MAFs, ever, or doomed you be. use only ROCKAUTO.com they ban this crap for sure.

RE: Low 5v ref - fixkick - 01-31-2021

C103 love to fail most of all.
bad caps. (use Nichicon brand 205C rated) Japan Caps. not china counterfeits.
if dead, (dried out inside or leaking green acid or split or measures 0uF not 47uf the cap is BAD)
when the cap fails the regulator IC7 loves to go nuts. and ECU reboots endlessly and horrible effects. from that.
bad caps
bad 5v
injectors dead (mostly just 1), due to transistor bank MPI, failure are top 3 failures.

RE: Low 5v ref - Yukonjay - 01-31-2021

Hey thanks mr. Been lookn at your stuff for awhile. Ok your right is a 92. No iat sensor. I cut the wire back of ecu to take that guy out of equation. Yes the ecu will read exact same vol completely unplugged from the harness and gator clipped to batt on those 4 pins. Like I said takes a week or more for the vol to come back on one of my ecus?? Last time I ran it with the maf unplugged for a few days. Never showed low ref vol. just dropped off one day driving down the road. Time before ran for 3 weeks. Then lost the 5v sitting there idling. Um. Do you think the ecu that I’m using that keeps coming back up to 5v ish. 4.8 right now. Is bad? The other one is shot to H3ll. It crapped out bfo I found the bad maf. Thought I tested it but missed it somehow. Oh and my maf is a real one jus bad. Thanks for the info on the China crap ?. My pin 1 reads -.35. And it is a manual transmission.

Thanks!

RE: Low 5v ref - Yukonjay - 02-09-2021

Hey thanks mr. Been lookn at your stuff for awhile. Ok your right is a 92. No iat sensor. I cut the wire back of ecu to take that guy out of equation. Yes the ecu will read exact same vol completely unplugged from the harness and gator clipped to batt on those 4 pins. Like I said takes a week or more for the vol to come back on one of my ecus?? Last time I ran it with the maf unplugged for a few days. Never showed low ref vol. just dropped off one day driving down the road. Time before ran for 3 weeks. Then lost the 5v sitting there idling. Um. Do you think the ecu that I’m using that keeps coming back up to 5v ish. 4.8 right now. Is bad? The other one is shot to H3ll. It crapped out bfo I found the bad maf. Thought I tested it but missed it somehow. Oh and my maf is a real one jus bad. Thanks for the info on the China crap ?. My pin 1 reads -.35. And it is a manual transmission.

Thanks!

RE: Low 5v ref - fixkick - 02-09-2021

(02-09-2021, 05:45 AM)Yukonjay Wrote: Hey thanks mr. Been lookn at your stuff for awhile. Ok your right is a 92. No iat sensor. I cut the wire back of ecu to take that guy out of equation. Yes the ecu will read exact same vol completely unplugged from the harness and gator clipped to batt on those 4 pins. Like I said takes a week or more for the vol to come back on one of my ecus?? Last time I ran it with the maf unplugged for a few days. Never showed low ref vol. just dropped off one day driving down the road. Time before ran for 3 weeks. Then lost the 5v sitting there idling. Um. Do you think the ecu that I’m using that keeps coming back up to 5v ish. 4.8 right now. Is bad? The other one is shot to H3ll. It crapped out bfo I found the bad maf. Thought I tested it but missed it somehow. Oh and my maf is a real one jus bad. Thanks for the info on the China crap ?.
My pin 1 reads -.35 this is wrong. ,this means MAF has no 12vdc power, and is wrong.
And it is a manual transmission. 5SP M/T SURE. and very good to have.

Thanks!

+5VREF PIN IS SPEC, 4.75 TO 5.25V

ONLY 3 Things make it fail for low.
bad sensors. (shorted)_
shorted wires to any sensor.
ECU bad....
keep in mind all things electronic can be good , bad ,intermittent or fails only hot or cold. that is there THING.

the IAT must be present if the ECU is IAT active (p./n of ECU tells that)
if the ECU 92 no IAT active, then , IAT it does not matter at all, (that 92 non IAT ECU DOES NOT SCAN THAT PIN SO CANNOT FAIL FOR IAT EVER)
if the ECU wants , IAT present (newer ECU) , and ITA is missing or wires cut to it the ECU WILL GO TO LIMPHOME MODE. (rich burn , no spark retard and lower power)

The 5vdc REF power is not optional ever, when 5vdc fails 5vref., fails the TPS will fail first. for low voltage.
the dome fuse must be present or DTC errors will not be stored. (in DTC RAM memory)

maf RUNS OFF 12VDC BATTERY. NOT 5VDC LIKE OTHERS DO.

MAF pin Out list: (typ. 92-95’) USA ! models. The Suzuki and GM GEO books, name the pins backwards but the colors do not lie.

1--- Blue/black ---- Main +12vdc power (IF THIS IS 0V, AS YOU SAID THE WIRE IS CUT.) THE MAF HAS NO POWER.

2--- Gray/black --- MAF output signal 1 to 5v , proportional to Air flow. B8 (HOT IDLE 800RPM IS 1.7–2.0 volts.) 3 TO 4VOLTS WIDE OPEN THROTTLE FULL ENGINE LOAD (HILLS)

3--- Black ---------- Ground. 0VOLTS. (put DMM meter black lead to BATTERY NEG - LUG and RED test lead probe (back probing all 3 at idle) this pin is 0v. ground.

Blue/black MUST BE 13.3 TO 15V RUNNING, THIS IS ALTERNATOR VOLTAGE SPEC. from main relay out;
see wiring here page 9 mAF, colors matter,
pin 2 is MAF out, gray /black.

https://fixkick.com/power-elect/95%20electrics/95FSM-ECU-MPI-Tracker.pdf

good luck !

RE: Low 5v ref - fixkick - 02-09-2021

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.