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IP or electrical problem?

H

Hans

New Member
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16
Location
Norway
I keep getting pump and other codes and need some help figuring this out. The truck is a 95 K1500. Started out earlier this year with first a no start and then hard start with pump codes, ran the atf through the pump a few times and it cleared and worked fine for a short time and then it started to act up again and I was getting bucket loads of codes, the IP codes where the same but the rest was different each time. unplugged the rear harness and it cleared out, found there was water in the extra led backup lights I had installed. After I removed these it ran fine for a few days until I parked it and went away for work.
Came home last week and hooked up the caravan for a trip stopped at the mall for some supplies and didnt get any further,a short in the starter motor. Borrowed another truck and got the trip done. Have now changed the starter and it ran fine.
Today I was going to haul a load of firewood and after about 30 minutes it stumbles and the check engine light comes on, stops and restarts and everything is fine, this repeats a couple of more times and then it doesnt help to restart. According to ALDLDROID the timing on the pump is stuck at 25.5.
Checked the codes and got this list.
16 - Vehicle speed sensor buffer fault
17 - High resolution circuit fault
18 - Pump cam reference pulse error
35 - Injection pulse width error (response time long)
36 - Injection pulse width error (response time short)
49 - Service throttle soon lamp circuit fault
54 - PCM fuel circuit error
84 - Accelerator pedal position circuit fault
99 - Accelerator pedal position 2 (5volt reference fault)

Cleared the codes and went another 5 miles to my destination, checked the codes again and had:

16 - Vehicle speed sensor buffer fault
17 - High resolution circuit fault
18 - Pump cam reference pulse error
35 - Injection pulse width error (response time long)

Cleared the codes again and restarted while parked and checked codes and 18 and 35 come on right away, checked with GMTDScan while trying to start, it has a long crank and doesnt start until the software has detected 8 missed cam references.

Another thing I have noticed is when I have this problem I get zapped with static every time I exit the truck.

Things that I have done, have checked grounds and added extras for good measure. Rewired the pump harness, the pmd is located in the front bumper. Had the complete engine wire harness out and checked all wires and contacts and measured the resistance in every cable. Checked with clear hose for air in fuel, checked lift pump and it delivers plenty fuel.

Any ideas where I go next?
 
You say checked grounds. Remove clean both surfaces of connector, what it is connecting to, and the fastner. Then Reinstall.

Undo and clean all battery connections.
Remove and clean the ground to the ecm.

It sounds like the tuck is an electrical mess. Patiently go froM front to back and correct the issues.
 
A PMD going out will throw some of the IP codes. Have you tried a good spare PMD.
 
If he's getting zapped when he touches the door wouldn't that more possibly be a body ground or harness ground?
 
My 97 zapps me when she feels like it..I think it when she don't like the injector cleaner I buy her that day.. ornery old ( (deleted))
 
Took off all the grounds today cleaned and ground everything down to bare metal, also added redundant grounds so each ground point is now attached to two other ground points in the hope if one of them is bad it will jump to another and still work.
Still had the problem with long crank on startup afterwards, went for a drive and checked the codes afterwards. And the list was quite extensive.
And I dont believe they are all real, for instance the 49 - Service throttle soon lamp circuit fault I see the service throttle soon lamp come on every time I start up.

Here is the list I got:
16 - Vehicle speed sensor buffer fault
17 - High resolution circuit fault
18 - Pump cam reference pulse error
35 - Injection pulse width error (response time long)
36 - Injection pulse width error (response time short)
44 - EGR pulse width error
45 - EGR vent error
49 - Service throttle soon lamp circuit fault
57 - PCM 5 volt shorted
62 - Turbocharger boost sensor circuit low
 
Any chance the voltage regulator is messing up..mine threw many of the same codes back quit a while ago.. I went through two generic ( dorman)( I think) crank position sensors and temperature control centers before somebody on this forum told me to get ACDelco ones... I bought AC Delco on sensors and also bought a new alternator at the same time and installed all three at the same time...It fixed the problem but I can't honestly say which one fixed it...just a thought..but some of these other guys know more about it than I do
 
The alternator sounded plausible so I tried removing the cables from it and took off the belt to see if that made a change but no joy.
Was wondering if the TPS could have something to do with it as on the last trip it kept ticking at 1500 rpms, had to brake and gently tap the throttle before it let go. So could a bad TPS be the cause of the other errors or is it the other fault that is affecting the TPS.
 
I have now gone through the DTC checklists for the most common codes I have and need some help with the results.

First DTC 17 &18
checked for 5 volts on terminal A on the optical sensor harness and valid ground on D both checked out.
For 17 disconnected shutoff solenoid and checked voltage on PD9 while cranking, got 4.6Volts (Should have been 2-3) which then points to a faulty OFTS.
for 18 set idle to 900 and measured HZ on PD15 and get around 150HZ According to the test I should have had 60 which again points to a faulty OFTS.

DTC 35 says that it sets an injection pulse width to 1.95, mine is at 1.62 and does not fluctuate when accelerator is pressed. Can also mention that my TDCO is -0.26 degrees and timing is 0 with no changes.

DTC 57 the checklists asks for less than 4 volts on pin c I have 5 volts, also checked pc10 and pd10 for ground and there was none so that check passed.

When codes where cleared now all that came in was 17 18 and 35 when sitting idle in the driveway, clearing the codes while it was running instantly brought back 18 and 35.

So what is the verdict? new pump, new OFTS or rip out all grounds and redo them and see if that helps?
 
I just replaced a pump on a customers 94 that had codes 17 18 and 35. Gm has a TSB to replace the pump if those codes are present. Obviously check your wiring first but I'm willing to bet you need a pump. But I would diagnose the 57 code first. Either you have a shorted wire or a sensor that is shorting out the 5v ref. If the 5v ref gets shorted it will affect every sensor on that circuit. I see that all the time with the powerstroke and Cummins. Exhaust back pressure sensors like to short out and cause all sorts of issues.

And to check OP and CPS properly you need a lab scope.
 
To test the OS you need to unplug the CPS and then try and start it. It will take extended cranking and will start in Limp mode. If it runs smoothly then the OS is OK. To test the CPS you unplug the OS and do the same as with the OS.
 
So you did the grounds... Now look at the "positive". What is the ECM telling you it is seeing on the scanner for voltage? Low voltage to a computer (aka ECM) causes a "1" to be seen as a "0" because it can't get the voltage high enough to write a "1". Things get FUBAR quick when this happens.

Couple places to check positive cables for shorts: passinger side battery tray rubbing through positive cable: and the mess of wires that go between the starter heat shield. Battery cable insulation can fall off in the oven there.

Now looking at the codes a "Short" is a good place to start as others noted: a 5V short can affect many sensors that need the 5V. ECM's do weird things when outputs are shorted...

So I would look at these as 57 "short" ... the code is still coming up so you are not done with it. I suggest code 62 is where you need to start. Circuit low means a short could be causing it. (Broken or corroded wire/connection is common as well.) Code 49 - does the Service Throttle Soon light work? Was the bulb removed? It's possible the bulb or socket shorted: Not likely, however, it's a clue.

49 - Service throttle soon lamp circuit fault
57 - PCM 5 volt shorted
62 - Turbocharger boost sensor circuit low
99 - APP could be or is affected by the short.

FYI:
Bug or Ghost codes on 1995. If you don't wait 30+ seconds after key off before you turn the ignition back on the ECM likes to pop an APP code. Also the SES and STS lights during a bulb check are completely random. The ECM is still "alive" and sending APP data to the scanner for around 30 seconds after key off. Bluntly you cycled the key from on-off-on too fast if you don't get both a SES and STS light when the key goes to on. (I forget what code it was but my long gone 1995 would pop a APP code if I cycled the key too fast.)

84 - Accelerator pedal position circuit fault
99 - Accelerator pedal position 2 (5volt reference fault)

Intermittent shorts are not fun.
 
Ok tested the OS and CPS, there is no change in how it behaves or what codes I get with OS plugged in or unplugged. With the CPS unplugged and Os connected there is no start.
Reading the voltage from the ECM says 13.5Volts on battery voltage with engine running and 1.3 Volts on the Voltage reference sensor.
 
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