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Old 12-22-2009, 04:28 PM   #1 (permalink)
manest
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Bad PCM??? Diagnostic checklist included

I have several issues with my truck: hard start cold, cruise kicks out, and check engine light (DTC36 and 88). After researching my problems I thought that my PMD would be the most likely cause because of the hard start and the cruise kicking out.

I got GMTDScan tech so that I could set the pump timing. I tried to do this and the DTC88 will not clear, nor can I set the TDC offset. The stepper motor seems to run correctly because the desired timing matches the measured timing. However the TDC offset is always 0*. So now I am thinking that I might have a problem with the PCM.

I have read alot on this forum and tried to find the answer to my problem with all the outstanding advice on this forum. But I haven't found the answer yet so here is my diagnostic checklist all filled out and hopefully someone will have some insight as to my problem.

1. Describe the problem you are having in detail:

hard start cold [engine temp] (extended GP time fixes), cruise kicks off, and check engine light. Throws DTC 36 (injector pulse width error response time too long) and DTC 88 (TDC Offset error) all the time.

2. Year of truck/engine.

1994 for both

3. Odometer reading (indicate miles or kilometers).

154200 miles

4. Indicate the model number on the Injection pump (starts DS4 or DB2......).

DS4 831-5521 manufacture date:2/27/2003

5. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD.

K2500

6. Do you have an EGR on the engine?

No, vin F

7. Air Filter condition (visual check).

Clean

8. Fuel filter condition (freshly changed, mileage since changed).

unknown

9. Location of PMD/FSD? (ex. on pump/remote over intake, behind bumper).

Stock, on side of IP.

10. Outside Temperature (C or F). _____

60* F although outside temperature seems to have no effect on problems.

11. Service Engine Light while running?- on/off/intermittent

Yes, off when first started and driven then comes on after driving a short distance (1/4 mile)

11a. Service Engine light does glow during start/cranking/bulb check: Yes/No

Yes

12.Have you scanned for engine codes? Yes/No

Yes

12a. List exact results on engine codes.

DTC 36 Injector pulse width error (reponse time too long)

DTC 88 TDC offset error (will not clear)

13. Condition of Battery terminals (removed, cleaned and tightened).

Excellent

14. Known condition and age of Batteries.

Hold good charge, both 1 year old

14a. Are batteries a matched set of same age?

Yes

15. Condition of Major Grounds (removed, cleaned and tightened)

Excellent

16. Does engine crank, or "turn over"?

Yes

16a. Does engine start and run?

Yes

17. If engine does not start- Crack injector line: do you have fuel? Yes/No

N/A

18. Does your Wait To Start light come on?

Yes

18a.Number of seconds WTS light is lit.

15 seconds on PCM control

19. Engine Cranking speed (if you have an accurate tachometer).

unknown

20. Are you experiencing Stalling?

No

21. Check turbo inlet and air filter for obstructions.

Clear

22. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now?

N/A

23. Lift pump test - Describe results.

good flow, 8psi at idle.

24. Upon cold start, does the radiator hose get hard quickly? Yes/No

No

25. Upon cold start, do you have excessive white smoke? Yes/No

No

26. Do you have excessive cranking time before the engine starts? Yes/No

if not using the glow extender, yes

27. Have you used the block heater? Does it affect engine starting? (only try for starting problems).

Yes I have one, no it doesn't affect starting. (only used it once)

28. Are all glow plugs in proper working order?

Yes

29. During hard acceleration, do you have excessive black smoke? Yes/No

Yes

30. Do you have any unusual exhaust smoke issues?

unknown

31. Turbo check out - Pass/Fail

Pass, 7 PSI Max 2-3 PSI crusing

32. Indicate fuel that you are using: Bio-Diesel, #2 Diesel, SVO/WVO, other

#2 Diesel from local truck stop

33. Are you using any fuel additives? If so, please list.

No

34. Upon unscrewing fuel cap, do you have a large vacuum formed in the
tank? Yes/No

No

35. Do you have any service history available that might pertain to the problem you are having?

No

36. Please indicate any modifications to the vehicle that might help us diagnose better.

See signature, I also have GMTDscan tech

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1994 K2500 ext cab, 6.5TD vin F, 4L80E trans, 4.10 gears.

Mods: Bumper mounted FSD and cooler, Homemade "turbomaster", Issopro boost gauge and pyrometer, fast idle switch, coolant temp "fooler" switch, straight piped exhaust (stock size 2.5")

Last edited by manest; 12-22-2009 at 04:57 PM.
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Old 12-22-2009, 09:27 PM   #2 (permalink)
ak diesel drive
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try disconnecting the batts for awhile to clear codes. You can't set timing (tdco) with codes present. You might have to rotate your IP to the pass side to get it to run without coding.

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96 k2500 214000 miles GL4, turbomaster, 4" exhaust, vac pump delete, marine injectors, -1.94 TDCO
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Old 12-23-2009, 12:17 PM   #3 (permalink)
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Quote:
Originally Posted by ak diesel drive View Post
try disconnecting the batts for awhile to clear codes. You can't set timing (tdco) with codes present. You might have to rotate your IP to the pass side to get it to run without coding.
I've tried the battery disconnect and it still codes the 88 as soon as the key is turned on, without the engine running. Basically DTC88 is always present.

I will try retarding the pump and see if that stops it from coding. Thanks
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1994 K2500 ext cab, 6.5TD vin F, 4L80E trans, 4.10 gears.

Mods: Bumper mounted FSD and cooler, Homemade "turbomaster", Issopro boost gauge and pyrometer, fast idle switch, coolant temp "fooler" switch, straight piped exhaust (stock size 2.5")
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Old 12-23-2009, 12:52 PM   #4 (permalink)
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http://www.bsecorp.com/files/techtips/bdtecb203.pdf
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Old 12-23-2009, 01:02 PM   #5 (permalink)
JMJNet
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So did you put a !! NEW !!! PMD already.
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PMD in Bumper
Leroy Diesel Flight System PMD
Leroy Diesel Oil Cooler Line
4" Warpspeed Exhaust
Kennedy Diesel LP/OPS Harness
Bosch Duraterm GP
Heath Turbo-Master
AD244 Alternator
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Old 12-23-2009, 01:23 PM   #6 (permalink)
manest
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Quote:
Originally Posted by JMJNet View Post
So did you put a !! NEW !!! PMD already.
No not yet. I was waiting to get the GMTDScan and set the timing before I completely condemed the PMD. Of course I am unable to set the timing because of the code 88 that resets immediately after clearing. I'm going to try and retard the pump and see if it stops the coding as suggested in a previous reply.
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1994 K2500 ext cab, 6.5TD vin F, 4L80E trans, 4.10 gears.

Mods: Bumper mounted FSD and cooler, Homemade "turbomaster", Issopro boost gauge and pyrometer, fast idle switch, coolant temp "fooler" switch, straight piped exhaust (stock size 2.5")
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Old 12-23-2009, 01:34 PM   #7 (permalink)
ak diesel drive
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Quote:
Originally Posted by DieselPro View Post

Interesting read but mine was at +3.85 when I scanned it with no codes and it ran pretty good. Definately not as good as the -1.94 it is now though.
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96 k2500 214000 miles GL4, turbomaster, 4" exhaust, vac pump delete, marine injectors, -1.94 TDCO
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Old 12-23-2009, 02:04 PM   #8 (permalink)
JMJNet
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Quote:
Originally Posted by manest View Post
No not yet. I was waiting to get the GMTDScan and set the timing before I completely condemed the PMD. Of course I am unable to set the timing because of the code 88 that resets immediately after clearing. I'm going to try and retard the pump and see if it stops the coding as suggested in a previous reply.

But now you are condemning the ECM? In rare cases that may be true. IMO, you may have a bad PMD or the whole IP is bad. If it cannot crank, with bad PMD, obviously, you cannot set the timing since it needs to be up to temp.
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1995 GMC Suburban:
PMD in Bumper
Leroy Diesel Flight System PMD
Leroy Diesel Oil Cooler Line
4" Warpspeed Exhaust
Kennedy Diesel LP/OPS Harness
Bosch Duraterm GP
Heath Turbo-Master
AD244 Alternator
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Old 12-23-2009, 02:28 PM   #9 (permalink)
manest
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Quote:
Originally Posted by JMJNet View Post
But now you are condemning the ECM? In rare cases that may be true. IMO, you may have a bad PMD or the whole IP is bad. If it cannot crank, with bad PMD, obviously, you cannot set the timing since it needs to be up to temp.
the truck cranks, starts (with extended GP time), and runs OK. My thinking on the bad PCM is that the DTC88 cannot be cleared by any method; scanner, battery disconnect, PCM disconnect, etc. Therefore I was thinking that the PCM may be faulty. Again is only an thought and I wanted to run it by people here before I go throwing $300+ parts at a problem.
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1994 K2500 ext cab, 6.5TD vin F, 4L80E trans, 4.10 gears.

Mods: Bumper mounted FSD and cooler, Homemade "turbomaster", Issopro boost gauge and pyrometer, fast idle switch, coolant temp "fooler" switch, straight piped exhaust (stock size 2.5")
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Old 12-23-2009, 03:18 PM   #10 (permalink)
manest
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OK I retarded the pump timing about 2mm past the 0* mark on the engine and I still get the same thing: with key on and engine off I clear the codes and recheck codes immediately and DTC88 is present (historic and current)

I have tried to clear the codes using all the methods I can think of: 2 different scanners, battery disconnect, PCM disconnect, and the procedure outlined in the GM service manual (key off, jumper A&B, key on, apply brake and accelerator pedals until it flashes DTC12, release pedals, DTC12 flashes again, key off and remove jumper). The code DTC88 (historic and current) remain when rechecked.

Originally I thought PMD because of their historic failure rate and I have several problems that point to that; hard start, cruise kicks out, and mediocre performance. I decided to get the GMTDScan tech to get the timing set up correctly and see if that was the cause of any of my problems and continual setting of the same codes (DTC36, 88) before I bought a new PMD. Plus I figured I needed a good scan tool for this truck since the other one (Acutron 4140) I have only reads/clears codes and didn't display all the sensor outputs for this application nor could it perform any of the timing tests.

This whole thing is not a huge issue for me as the truck still runs and drives OK. But I do want it to be right and run the best that is can. My end goal is a truck that gets decent mileage (15-20mpg), is dependable and has decent power (I can pass when I need to).

So any help is greatly appreciated

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1994 K2500 ext cab, 6.5TD vin F, 4L80E trans, 4.10 gears.

Mods: Bumper mounted FSD and cooler, Homemade "turbomaster", Issopro boost gauge and pyrometer, fast idle switch, coolant temp "fooler" switch, straight piped exhaust (stock size 2.5")
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