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I have a 97 C5 that has no communications on 10-PCM,28-TCS,40-BCM,80-radio,99-HVACAO-LDCM,A1-RDCM,B0-RFA, along with my temp gauge pegs out and no oil pressure on the gauge. I thought it might be my BCM so I purchased one that was re flashed went through the re learn procedures but got this same issue. HELP!
Sounds like a communication issue on the serial data bus…not knowing if you have any mechanical or electrical skills I won’t go any further…if none find an auto electric shop…is the car a no start or a start and stall ??
Vetteman Jack thanks for your response. Yes, the car starts and stalls but I Leave the battery disconnected and when I connect it back, it will start and run. I have mechanical skills and some electrical but trouble shooting wiring no. I did check all the grounds, checked the connectors in the door jams they all looked good. removed the top from the 4 wire data star connector no change. I did take it to a shop to get it looked at and paid a wreaker fee to get it there and brought it back home a month later the same way. People just don't specialize in 97 C5's because of all the electrical issues. I've been following post that have the same issue as mine and come to the conclusion that the PCM might be the problem but would like to make sure.
did you try resetting the PCM?
c5's use a slow-speed version of can called j1850, it's a peer-to-peer network similar to ethernet in its topology. if your PCM is bad, it could theoretically be continuously broadcasting and saturating the network.
The fact that you're even getting a comm error on the radio though... that usually means something physical.. double check all three main groudn points in the car, check the electrical connectors on the driver side -- j1850 isn't the best when it comes to interference, and any ground faults or shorts can result in the issues you're seeing --- Must Read for those with electrical problems. Fix with pics inside! - CorvetteForum - Chevrolet Corvette Forum Discussion
Sorry this isn't more of a help --- keep us posted!
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Try removing both bus bars or “combs” from both splice packs…jumper the PCM to BCM…dark green and light green wires…the car should start…if it doesn’t it either a bad PCM or BCM…video below…when the car is acting up with the key on you can either probe the purple data wire or pin 2 at the DLC and you normally see a fluctuating voltage of .2 to .8 or so…if you see voltage near ground the data line is shorted to ground or shorted to power if you see 12 volts.
So yesterday after work I hooked my battery back up and it started and stated running so I turned the car off removed the combs from both star connectors and tried to start it again just to see if it would start and it did and stayed running I turned the car off and de-pinned the dark green wire and the light green wire and tried to start it again and it started. I jumped the 2 wires together and it started.
So yesterday after work I hooked my battery back up and it started and stated running so I turned the car off removed the combs from both star connectors and tried to start it again just to see if it would start and it did and stayed running I turned the car off and de-pinned the dark green wire and the light green wire and tried to start it again and it started. I jumped the 2 wires together and it started.
If you removed BOTH star connectors the car will not start because the only 2 modules you need to communicate with each other is the BCM and PCM…you don’t have to de pin those 2 wires…if you have back probes just jump those 2 wires together…if the car now starts one of the other modules is the problem…with both combs removed and key on go pin to pin with a voltmeter and see if you read 12 volts or ground on any of the wires…if you want to de pin the wires keep the BCM and PCM connected together and then just keep adding modules until the car doesn’t start…that’s the bad module.
Thanks for your help you don't know how much I appreciate it and I'm with you it should not have started but it did and stayed running. knowing that these two connectors are used for programming and communications I could not believe it. I toke the combs off laid them on the floorboard. I de pin the two wires because I didn't have a probe that would fit but with the car able to start was really no point in the de pinning I tried anyway grasping for straws at this point. I'm going to get me a probe that I can use and try what you suggested as far as the 12 volts.
C5 Diag,yesterday I scoped my star connector for the modules here is the result HVAC Wht Wire .05, IPC Gry Wire .09-.19, Radio Org wire .0, BCM .11-.19,TCM dk blu/wht .0-.02, Dk Grn .11-.20, PPL .0 and my battery was over charging to up to 17 volts.
Do you mean a “scope” do you mean a DVOM ??…2 different pieces of equipment…only thing I see is radio at ground…were these reading key ON ???…you can just de pin that wire and reinstall both combs and see if the car runs.
So this weekend I de pinned the wire that goes to the radio the car still will start and stall. I keep the battery disconnected while I'm working on it and when I hook it back up it will start and run. I turn it on and off several times until it apparently cycles out and it returns to the same start and stall.
If jumping the PCM and BCM allowed the car to start and run just de pin all the other wires with both “combs” installed and add them one by one until the car doesn’t run…the purple is the data line so don’t disconnect that one.
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