NO Start
Post Fiend
Joined: Dec 2010
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From: Orrville, Ohio
Ugg, I was really hoping your issues were behind you. Ok, lets start from square one. Have you tried a different PCM? I think you have tried cranking it with the ICP unplugged haven't you?
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I have not tried a different PCM.
Presently, it will not start if I unplug ICP.
When my voltage going to signal wire of IPR was at 0.36 it would start with ICP unplugged. Now that voltage is 1.36 again and there isn't even a hint of smoke or firing. If I unplug the 42 pin connector and check the voltage coming out of the PCM at the yellow/red wire the voltage is still 1.36. That would eliminate the engine harness. So, I believe it has to be in the PCM grounding problem. I did a continuity check on the PCM grounds a couple of weeks ago and they were good. But at that time I had 0.36 volts. Now, no amount of wiggling wires or connecting and disconnecting the PCM or IDM connectors changes that voltage. At one point that voltage was showing up on one of the small leads on my GPR, but it is okay there and now back on the IPR signal wire.
2 new CPS
New ICP
New IPR
New Fuel pump and filter
New Air cleaner
Some new pigtails, new glowplugs
Under the valve wiring harness ohmed good.
Seems to be a ground problem. Tired of just buying parts.
Presently, it will not start if I unplug ICP.
When my voltage going to signal wire of IPR was at 0.36 it would start with ICP unplugged. Now that voltage is 1.36 again and there isn't even a hint of smoke or firing. If I unplug the 42 pin connector and check the voltage coming out of the PCM at the yellow/red wire the voltage is still 1.36. That would eliminate the engine harness. So, I believe it has to be in the PCM grounding problem. I did a continuity check on the PCM grounds a couple of weeks ago and they were good. But at that time I had 0.36 volts. Now, no amount of wiggling wires or connecting and disconnecting the PCM or IDM connectors changes that voltage. At one point that voltage was showing up on one of the small leads on my GPR, but it is okay there and now back on the IPR signal wire.
2 new CPS
New ICP
New IPR
New Fuel pump and filter
New Air cleaner
Some new pigtails, new glowplugs
Under the valve wiring harness ohmed good.
Seems to be a ground problem. Tired of just buying parts.
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Senior User
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Okay here is what I did today.
I spliced into the signal wire going into the IPR and while touching the other end of that wire to the B- I brought the volts down to 0.00. I turned over truck and with the signal wire grounded the truck immediately started, so then I cut the yellow/red signal wire 6-8 inches from the PCM and jumped it to the IPR connector, bypassing the 42 pin connector and the complete yellow/red wire.
I tried to start truck and it would not start. The volts were back to the 1.36 volts. Looks like I probably have a bad PCM ground or the PCM is bad. At least this test eliminates a ton of stuff, like CPS, IPR, ICP, etc.
I spliced into the signal wire going into the IPR and while touching the other end of that wire to the B- I brought the volts down to 0.00. I turned over truck and with the signal wire grounded the truck immediately started, so then I cut the yellow/red signal wire 6-8 inches from the PCM and jumped it to the IPR connector, bypassing the 42 pin connector and the complete yellow/red wire.
I tried to start truck and it would not start. The volts were back to the 1.36 volts. Looks like I probably have a bad PCM ground or the PCM is bad. At least this test eliminates a ton of stuff, like CPS, IPR, ICP, etc.
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I have checked the voltage on the red wire and it is always over 12.
When I check continuity of signal wire though I was always getting around 900ohms which showed a problem, but I am not sure if the way I checked it eliminated the PCM as the problem. As I recall that continuity check was wirh pcm connected. I live in Bakersfield Ca.
When I check continuity of signal wire though I was always getting around 900ohms which showed a problem, but I am not sure if the way I checked it eliminated the PCM as the problem. As I recall that continuity check was wirh pcm connected. I live in Bakersfield Ca.
Post Fiend
Joined: Dec 2010
Posts: 10,121
Likes: 3
From: Orrville, Ohio
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Thanks Nate, but I have an automatic. How would I get a part number for the PCM? There was a piece of paper on the front of mine, but it was ripped and faded, couldn't make anything out. I don't have the PCM out of truck yet. Mine is a 1995 built in Jan 1995.
Post Fiend
Joined: Dec 2010
Posts: 10,121
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From: Orrville, Ohio
I don't think it really matters. The PCM is what has the code in it that you have to match, so if you're replacing the PCM, as long as it is from an OBS with a PSD and an automatic trans and is either 49 state or cali (which ever your truck is), you should be good to go. Someone else may be able to chime in and let you know what the latest version was, but I don't know of the top of my head.
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Took the PCM out, the part number is F5TF-12A650-BJF.
What does the BJF mean compared to a BJE?
No chip in my PCM btw.
This is interesting though. I noticed that inside the PCM there appears to be a bunch of grounding lugs that when the PCM is installed they contact the metal surface the PCM sits in and from what I can tell it is used for grounding the PCM. Or is it to discharge static electricity from the box?
What does the BJF mean compared to a BJE?
No chip in my PCM btw.
This is interesting though. I noticed that inside the PCM there appears to be a bunch of grounding lugs that when the PCM is installed they contact the metal surface the PCM sits in and from what I can tell it is used for grounding the PCM. Or is it to discharge static electricity from the box?
Post Fiend
Joined: Dec 2010
Posts: 10,121
Likes: 3
From: Orrville, Ohio
Not totally sure on the PCM codes. Sorry. What I do know about them is that you have to have one programmed (flashed) for your auto transmission. I also know that prior to '95 the PCM's did not include the programming to operate your OBD II port. Now you could always have the PCM "re-flashed" to the latest and greatest program by your dealer, or even by some tuners. They can actually flash a tune to your PCM, just like having a chip, but it's always on the same tune. I know DP Tuner does this and I am pretty sure some others do too.
Post Fiend
Joined: Dec 2010
Posts: 10,121
Likes: 3
From: Orrville, Ohio
AHAH! Here is the link I was searching for. I knew I had seen this somewhere but apparently I didn't bookmark it...until now.
I can't find that number in the list though. Any chance there is another number on the PCM?
EDIT: Just found them both near the bottom (about 7/8 of the way down) of the page. You just have to take out the numbers in between the 5FTF and the three letter suffix. They appear to be identical.
I can't find that number in the list though. Any chance there is another number on the PCM?
EDIT: Just found them both near the bottom (about 7/8 of the way down) of the page. You just have to take out the numbers in between the 5FTF and the three letter suffix. They appear to be identical.
