PCM IDM Problem
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Freshman User
Joined: May 2018
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From: Boise, Idaho
PCM IDM Problem
I have done all the trouble shooting for a faulty IDM, what I have came up with is a weak or no signal from the PCM to the IDM relay. The relay is good but it gets no signal or very weak signal. Do I need to replace the PCM or is there something else I need to check and if I do need to replace the PCM who is a reputable supply I should use?
Postmaster
Joined: Nov 2015
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From: Colorado Springs
If you want the both tested and potentially repaired get a hold of Jonathan. Great work and quick turn around time.
https://www.dieseltechchatt.com/
https://www.dieseltechchatt.com/
Lead Driver
Joined: Apr 2011
Posts: 8,259
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From: Northern California
dont forget, the signal passes between the 2 via wires, wires that at times break, chaff or otherwise fail to allow a signal to pass.
have you checked connectivity from end to end on the circuit in question ?
which pins on the PCM side are you tracing ? ( just curation as I want to look at the wiring diagram and follow along )
have you checked connectivity from end to end on the circuit in question ?
which pins on the PCM side are you tracing ? ( just curation as I want to look at the wiring diagram and follow along )
Lead Driver
Joined: Apr 2011
Posts: 8,259
Likes: 346
From: Northern California
on the factory wiring diagram the only white black wire I see goes from the IDM power rely to the PCM
that may or may not indicate an issue with the IDM.
the DG/LG wire that comes out of the IDM power relay on the #87 leg and goes to the IDM.
the more concerning wire to the IDM power relay is the white/LB that comes from the PCM Relay,
that wire comes out of the central control box but not before it goes through the Fuel bowl heater/water in fuel circuit
have you checked your fuse 30 which powers the PCM ?
crazy as it sounds both the PCM and IDM rely on a power wire that goes through the fuel bowl, if the fuel bowl heater shorts then it blows fuse 30 which kills power to the PCM and IDM.
that is where I would be investigating if you have not already done so.
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Freshman User
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From: Boise, Idaho
I will check the fuel bowl in the morning, and trace the wire from there and check the wire that runs on the valve cover again and let you know what I find. Thank you pirate4x4
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There are several wires diagrams in the 7.3L PSD Tech Folder that may aid in your troubleshooting. Based on what you have said, if I were you I would be sure there is not a wiring fault before sending the PCM off. Jonathan does a great job, but that might not be your issue.
Laughing Gas
Joined: Jun 2017
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From: CSRA, SC
Just a side note, checking the wires end to end doesn't tell you everything you need to know. Also check they have not shorted to ground or to 12V. Previously mentioned chafing issues wont show up if you only check them end to end.
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Freshman User
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From: Boise, Idaho
This morning after checking all the wires again and testing the white/LB wire I have come to the conclusion that it must be the PCM is malfunctioning in which it couldn’t come at a better time. I will be replacing and upgrading a lot of worn out parts on my truck that has 345k miles on her and has never really been touched everything except the torque converter Saginaw power steering pump and a few other notorious wear parts are original. I am upgrading to 1.5 injectors, irate’s complete regulated fuel system (also considering building my own since I like to do those type of things on my own), rebuild or upgrade drop in turbo haven’t decided yet, hydra chip, and all of the other miscellaneous things that come along with those. So would I be better off if I rebuilt the PCM to stock programming or should I rebuild/replace with performance programming? Does the hydra take care of all the programming or would I get a little bit more performance with a performance PCM? I am building the truck to be a daily/hauler, maybe one day a hot rod.
Postmaster
Joined: Nov 2015
Posts: 4,807
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From: Colorado Springs
This morning after checking all the wires again and testing the white/LB wire I have come to the conclusion that it must be the PCM is malfunctioning in which it couldn’t come at a better time. I will be replacing and upgrading a lot of worn out parts on my truck that has 345k miles on her and has never really been touched everything except the torque converter Saginaw power steering pump and a few other notorious wear parts are original. I am upgrading to 1.5 injectors, irate’s complete regulated fuel system (also considering building my own since I like to do those type of things on my own), rebuild or upgrade drop in turbo haven’t decided yet, hydra chip, and all of the other miscellaneous things that come along with those. So would I be better off if I rebuilt the PCM to stock programming or should I rebuild/replace with performance programming? Does the hydra take care of all the programming or would I get a little bit more performance with a performance PCM? I am building the truck to be a daily/hauler, maybe one day a hot rod.
The Hydra gives you almost endless tunes, that alone makes it better than just one tune on your PCM. If you send it in to Jonathan he can repair it and get it ready for the Hydra.
Lead Driver
Joined: Apr 2011
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From: Northern California
i will wager that the performance tune Johnathan offers to install is superior to the vast majority of all tunes offered for the hydra platform.
hate to say this but i got sick and tired of the johnny come lately tuner of the month game while they experimented on my daily driver at my expense long ago. i went back stock awhile back after Johnathan rescued my rare and almost irreplaceable PCM.
i no longer trust anybody but him to fuss with my 7.3 pcm or tuning. not worth the risk.
hate to say this but i got sick and tired of the johnny come lately tuner of the month game while they experimented on my daily driver at my expense long ago. i went back stock awhile back after Johnathan rescued my rare and almost irreplaceable PCM.
i no longer trust anybody but him to fuss with my 7.3 pcm or tuning. not worth the risk.
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