Just had my GM mechanic buddy in town for a visit so we did a few things to my 94 6.5. He showed me how to change the fuel filter and we checked the codes. It has been stalling for a split second under load but has not cut out completely. I know all about the PMD problem and I am mounting a heat sink with a new PMD inside the bumper nostril this weekend. However the codes that have been set are the 'death codes' for my IP. Can't remember all the #s. There were at least 3 or 4 different ones. I plan to run this one until it dies completely as I have no long trips planned for this summer. When purchasing a new one, rebuilt or new? Is there info on replacing them online? I watched my mech. buddy do one a couple years ago & may tackle it myself. Is it possible that it is only my PMD?

'Death codes'? Oh, THOSE death codes.

The ones I had 4 yrs ago.

Codes 18, 35, 36, and 54 ring any bells?

On the advice of Bill Heath and several of the guys on here, I replaced my PMD, changed my fuel filter, and started to run 8oz PS Silver and 8oz 2-stroke-oil in every tank (now I'm down to 4 oz of each per tank).

Strangest thing... that was 100,000 km ago. The local GM dealer keeps telling me that my IP is just 'living on borrowed time', because of the codes he read 3 years ago.

In memory of George Carlin, there are 7 words you cannot say on television, and I reserve all of them for the GM dealer. He was wrong then, and he's wrong now.

As for you, I hope you're that lucky... pay close attention to the many threads on here about how to properly relocate your PMD (mounting it to the heatsink with thermal paste, making sure you retrieve your calibration resistor from the old PMD, properly lengthening your harness, one wire at a time, by soldering and heat-shrink tubing, protecting it with a wire loom, and then adding additive in every tank to lubricate the IP.

Don't guess... if you need to know something and aren't sure, ask. Lots of people here will help you out.

Even if you ARE from BC and wish you had a football team ... <grin>

Yep code 18,35,42. Thanks for your quick reply. I thought we did have a football team until this year.....what happened?

Just checked the codes again so I could give you guys a better idea of whats going on. I have code 18,29,35,42,46,57,62,71,84,99. Just about the whole book eh? Thanks again for your help. I will go and clear those codes now and see what else comes up this week.

Just checked the codes again so I could give you guys a better idea of whats going on. I have code 18,29,35,42,46,57,62,71,84,99. Just about the whole book eh? Thanks again for your help. I will go and clear those codes now and see what else comes up this week.

Assuming the batts, grounds, fuel filter, and LP circuit are all fine.
I'd suggest you actually perform an air leak test.

1. Remove both the fuel supply line and fuel return lines at the fuel tank.
DO NOT PRESSURIZE THE FUEL TANK.
2. Plug the return line.
3. Insert a valve stem into the supply line, I cut one from a bicycle inner tube..
4. Using a bicycle hand pump with a built in pressure gauge, pressurize the fuel system to no more than 20 PSI while observing the pressure gauge and listening for any leaks.
5. Check thoroughly for fuel/air leaks and repair as necessary. The air pressure may force fuel out the leak making it easier to locate. Fix all leaks till it holds steady pressure for at least 30 seconds or more.
If you find one or more air leaks, chances are thats what triggering all them DTC(s).
6. Reconnect fuel lines.
7. Bleed air from the fuel system.
8. Clear engine DTC(s) and go for a test drive.

I had nearly the same exact DTC's on my '95. After spending 40 days and $2500.00 at an authorized GM Service Center,, I still had the very same DTC's and driveability symptoms present as I had DAY 1.
Driveability symptoms~Hard starts and stalling with the occassional miss.
GM replaced the ECM/PCM 3X's, Optical Sensor 1X, Injection Pump 3X's, Timing Chain 1X, all based on DTC(s) alone.. I should mention all the stuff GM replaced was like new already.
All of it as a result of a faulty OPS read inop Lift Pump, which then exposed an air leak under the fuel manager/filter assembly, that turned out to be just a loose hose clamp on my new rubber fuel lines.
Do not skip Chapter one, Important Preliminary Troubleshooting/Checks as Id hate to see you go through the same BS...

I just replaced the fuel filter and drained the water trap a few days ago. I have now cleared all codes but one still remains. Oddly enough it is one that did not show up before - a code 17. I will do the test that you mentioned above. I just finished doing the snorklectomy and cleaned all battery connections and the ground behind the passenger side battery. I plan to clean the rest of the grounds tomorrow.

You DO realize that, if your OPS and lift pump had been working, an air leak wouldn't have caused any problems (other than leaking diesel fuel) - certainly wouldn't have caused any codes.

Your hard-luck GM story is a result of the technician's mistake in not checking fuel delivery pressure and lift pump operation; something you could easily have checked yourself, and which is an integral part of the troubleshooting checklist found in my signature.

You are forgetting that the 6.5 is a lift-pressurized fuel delivery system. The IP only 'sucks' fuel under cases when the lift pump quits or there is a line blockage.

Air leaks only cause issues under suction in a fuel system.

This ain't a gas engine.

Personally, if your lift pump is functioning properly, I wouldn't bother going through with the air leak test unless you have fuel coming out somewhere it isn't supposed to, and the easy way to determine that is to hotwire the lift pump and let it pressurize the system with the engine off, and look for leaks.

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Now - a DTC code 17 - High-resolution circuit fault - is not an air leak code, nor is it a lift pump code. As a mater of fact, neither of those conditions will cause that code. It is an electrical code, one of the few which directly result from PMD or optical sensor issues. It reflects an out-of-time response from the IP to an ignition event request.

- are you running a lubrication additive, such as 2-stroke motor oil?
- have you checked and/or replaced or removed your optical sensor filter harness?

Either of these two things might solve your problem. Interestingly enough, cloudy fuel or dirty fuel can also cause these codes to pop-up, which is also an opsensor issue. You haven't run any used motor oil in your fuel, have you (it's a serious no-no on these trucks)?

- are you running a lubrication additive, such as 2-stroke motor oil? Yes Esso synthetic blend outboard motor oil, 100 ML per tank

- have you checked and/or replaced or removed your optical sensor filter harness? No, I haven't touched it, should I remove it and inspect it?

take it off... the ends should plug back together without it, and the truck will run fine with it removed.

If it's the culprit, that'll show up right away.

I just installed my heat sink and mounted my PMD behind the bumper - I used heat sink paste and reused the GM gasket thingy. Just wondering if I should of used the gasket thingy? I also read that some have removed the plastic caps from the back of the PMD. I did not. The PMD is a used one off an old pump and it has given me a momentary stall already once towing 18 foot car trailer. I have a spare in the glovebox.

I just installed my heat sink and mounted my PMD behind the bumper - I used heat sink paste and reused the GM gasket thingy. Just wondering if I should of used the gasket thingy? I also read that some have removed the plastic caps from the back of the PMD. I did not. The PMD is a used one off an old pump and it has given me a momentary stall already once towing 18 foot car trailer. I have a spare in the glovebox.

You should run a bead of silicone around the base of the PMD/FSD were it mounts to the heat sink and also dab a little over each screw head to keep the moisture out. Mounted in the bumper seams to be the best place for it. But it is exposed to more environmental elements there (rain and so forth).