HELP!! Reduced Engine power, No Comms with PCM, BCM, TCS e.t.c
10-04-2009, 05:51 AM
#1
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HELP!! Reduced Engine power, No Comms with PCM, BCM, TCS e.t.c
Having what appears to be a common problem with no single cure. Went to fire up my '98 C5 but will not fire although the engine spins. The gauges are messed up the fuel reads empty, the temp reads hot e.t.c. The dashboard flashes low fuel, serv. traction system, reduced engine power, service engine soon.
Diagnostics read - 10PCM no comm
28TCS - U1255 HC (no comm)
40BCM - U1255 HC (no comm)
BORFA - U1000 HC (undetermined no comm)
Following up similar threads have checked on this forum (use this place like a text book its amazing!), cleaned and in some places replaced all earth points in engine bay/under kick panels e.t.c. Have checked all connectors in and through the doors. Checked all fuses and satisfied they all have and give power.
Has happened once before (few months ago) where the battery went dead and after charging showed up these exact faults.
I took the battery out for a while, made sure it was fully charged then on re-installation it was cured so must have reset something by disconnecting the battery?
Have tried doing this now its happened again but does not seem to cure the problem.
Am going to check all connections on the PCM itself today as it is the only unit showing no comms at all and hopefully will find a corroded plug or bad connection but any help would be really appreciated!
Diagnostics read - 10PCM no comm
28TCS - U1255 HC (no comm)
40BCM - U1255 HC (no comm)
BORFA - U1000 HC (undetermined no comm)
Following up similar threads have checked on this forum (use this place like a text book its amazing!), cleaned and in some places replaced all earth points in engine bay/under kick panels e.t.c. Have checked all connectors in and through the doors. Checked all fuses and satisfied they all have and give power.
Has happened once before (few months ago) where the battery went dead and after charging showed up these exact faults.
I took the battery out for a while, made sure it was fully charged then on re-installation it was cured so must have reset something by disconnecting the battery?
Have tried doing this now its happened again but does not seem to cure the problem.
Am going to check all connections on the PCM itself today as it is the only unit showing no comms at all and hopefully will find a corroded plug or bad connection but any help would be really appreciated!
10-04-2009, 08:56 AM
#2
Safety Car
I believe you're on the right track. If you've done all the grounds on the body I would suggest following the ground straps to the block and make sure they are tight and clean. Also, there is at least one ground connection at the back of the heads. This is the coil pack grounds and can be found at the back of the driver's side head. No ground to the coil packs, no spark.
Check and see if there was a battery leak or evidence of it. Look for acid residue in the tray and below it. A common problem has been the batteries go bad and leak acid. THe acid falls down and gets right on the PCM and the connector ruining one or both. If you find this has happened, baking soda and water, followed by a good non-residue contact cleaner could bring it back if the connector isn't to badly corroded.
No comms usually means the PCM has not booted, or it's in an indeterminate state, or it can't see the signals on the buss. If you have or can get access to a PCM programming package like EFILive you could use that to check and see if the PCM is awake from the OBDll port, i.e. you could check for the PCM checksum and module ID.
Best of luck on this. Again I believe you're going about this in the correct way. Start with the grounds and then divide the problem until the solution is found. Of course when it looks global it's hard to know where to start, but when it's in that condition you have to look for global causes: grounds, power, connectors, modules.
Check and see if there was a battery leak or evidence of it. Look for acid residue in the tray and below it. A common problem has been the batteries go bad and leak acid. THe acid falls down and gets right on the PCM and the connector ruining one or both. If you find this has happened, baking soda and water, followed by a good non-residue contact cleaner could bring it back if the connector isn't to badly corroded.
No comms usually means the PCM has not booted, or it's in an indeterminate state, or it can't see the signals on the buss. If you have or can get access to a PCM programming package like EFILive you could use that to check and see if the PCM is awake from the OBDll port, i.e. you could check for the PCM checksum and module ID.
Best of luck on this. Again I believe you're going about this in the correct way. Start with the grounds and then divide the problem until the solution is found. Of course when it looks global it's hard to know where to start, but when it's in that condition you have to look for global causes: grounds, power, connectors, modules.
10-04-2009, 10:52 AM
#3
Tech Contributor
Having what appears to be a common problem with no single cure. Went to fire up my '98 C5 but will not fire although the engine spins. The gauges are messed up the fuel reads empty, the temp reads hot e.t.c. The dashboard flashes low fuel, serv. traction system, reduced engine power, service engine soon.
Diagnostics read - 10PCM no comm
28TCS - U1255 HC (no comm)
40BCM - U1255 HC (no comm)
BORFA - U1000 HC (undetermined no comm)
Following up similar threads have checked on this forum (use this place like a text book its amazing!), cleaned and in some places replaced all earth points in engine bay/under kick panels e.t.c. Have checked all connectors in and through the doors. Checked all fuses and satisfied they all have and give power.
Has happened once before (few months ago) where the battery went dead and after charging showed up these exact faults.
I took the battery out for a while, made sure it was fully charged then on re-installation it was cured so must have reset something by disconnecting the battery?
Have tried doing this now its happened again but does not seem to cure the problem.
Am going to check all connections on the PCM itself today as it is the only unit showing no comms at all and hopefully will find a corroded plug or bad connection but any help would be really appreciated!
Diagnostics read - 10PCM no comm
28TCS - U1255 HC (no comm)
40BCM - U1255 HC (no comm)
BORFA - U1000 HC (undetermined no comm)
Following up similar threads have checked on this forum (use this place like a text book its amazing!), cleaned and in some places replaced all earth points in engine bay/under kick panels e.t.c. Have checked all connectors in and through the doors. Checked all fuses and satisfied they all have and give power.
Has happened once before (few months ago) where the battery went dead and after charging showed up these exact faults.
I took the battery out for a while, made sure it was fully charged then on re-installation it was cured so must have reset something by disconnecting the battery?
Have tried doing this now its happened again but does not seem to cure the problem.
Am going to check all connections on the PCM itself today as it is the only unit showing no comms at all and hopefully will find a corroded plug or bad connection but any help would be really appreciated!
Last edited by lucky131969; 10-04-2009 at 10:58 AM.
10-04-2009, 01:23 PM
#4
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I believe you're on the right track. If you've done all the grounds on the body I would suggest following the ground straps to the block and make sure they are tight and clean. Also, there is at least one ground connection at the back of the heads. This is the coil pack grounds and can be found at the back of the driver's side head. No ground to the coil packs, no spark.
Check and see if there was a battery leak or evidence of it. Look for acid residue in the tray and below it. A common problem has been the batteries go bad and leak acid. THe acid falls down and gets right on the PCM and the connector ruining one or both. If you find this has happened, baking soda and water, followed by a good non-residue contact cleaner could bring it back if the connector isn't to badly corroded.
No comms usually means the PCM has not booted, or it's in an indeterminate state, or it can't see the signals on the buss. If you have or can get access to a PCM programming package like EFILive you could use that to check and see if the PCM is awake from the OBDll port, i.e. you could check for the PCM checksum and module ID.
Best of luck on this. Again I believe you're going about this in the correct way. Start with the grounds and then divide the problem until the solution is found. Of course when it looks global it's hard to know where to start, but when it's in that condition you have to look for global causes: grounds, power, connectors, modules.
Check and see if there was a battery leak or evidence of it. Look for acid residue in the tray and below it. A common problem has been the batteries go bad and leak acid. THe acid falls down and gets right on the PCM and the connector ruining one or both. If you find this has happened, baking soda and water, followed by a good non-residue contact cleaner could bring it back if the connector isn't to badly corroded.
No comms usually means the PCM has not booted, or it's in an indeterminate state, or it can't see the signals on the buss. If you have or can get access to a PCM programming package like EFILive you could use that to check and see if the PCM is awake from the OBDll port, i.e. you could check for the PCM checksum and module ID.
Best of luck on this. Again I believe you're going about this in the correct way. Start with the grounds and then divide the problem until the solution is found. Of course when it looks global it's hard to know where to start, but when it's in that condition you have to look for global causes: grounds, power, connectors, modules.
I have been playing with the immobiliser on the car (locking and unlocking the doors e.t.c) and this has now allowed me to start and drive the car, although the comms issue with the PCM/BCM e.t.c still exist. All the warning lights are still on and the reduced engine power, traction system problems e.t.c still exist. Is the factory alarm/immobiliser a possible candidate for cause as it was a dead/low battery which started these chain of events. I have the original key but no remotes.
10-04-2009, 01:30 PM
#5
Tech Contributor
Thanks for the advice I will check all connectors and try to get a proper look at the PCM itself. Am I correct in saying the best way to get to it is removal of the passenger side wheel and remove the rubber/plastic trim to gain access? Or can you get access through the removal of the battery tray?
I have been playing with the immobiliser on the car (locking and unlocking the doors e.t.c) and this has now allowed me to start and drive the car, although the comms issue with the PCM/BCM e.t.c still exist. All the warning lights are still on and the reduced engine power, traction system problems e.t.c still exist. Is the factory alarm/immobiliser a possible candidate for cause as it was a dead/low battery which started these chain of events. I have the original key but no remotes.
I have been playing with the immobiliser on the car (locking and unlocking the doors e.t.c) and this has now allowed me to start and drive the car, although the comms issue with the PCM/BCM e.t.c still exist. All the warning lights are still on and the reduced engine power, traction system problems e.t.c still exist. Is the factory alarm/immobiliser a possible candidate for cause as it was a dead/low battery which started these chain of events. I have the original key but no remotes.
The PCM is fully accessible from the access panel behind the right front wheel.
PM sent.
10-05-2009, 02:12 PM
#6
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The VATS/TD system will result in one of two things: allows the engine to crank, but no start(fuel injectors cut off), or no crank. I help a shop troubleshoot this exact problem a few months ago, and it turned out to be a bad seat control module(drivers) and the class 2 was bringing down the rest of the system. As soon as he disconnected it, everything was restored. I'd be looking at the drivers door wiring, and seat control before messing with the PCM.
The PCM is fully accessible from the access panel behind the right front wheel.
PM sent.
The PCM is fully accessible from the access panel behind the right front wheel.
PM sent.
The problem has, though, started to become intermittent as I have driven it today for a few miles to see what happened.
Every now and then the gauges will return to normal and all the warnings will disappear with exception to the traction control symbol and on some instances the security symbol stays on but reduced engine power e.t.c is gone. In this instance I have managed to run another diagnostics check and the PCM can now be read. The only code it brings up is P1626 (theft deterrent system fuel enable circuit).
Strangely, the illumination on the climate control unit will come on and off as it feels too, even when all the lights are turned off.
The problem seems to be getting more confusing but i'm hoping some of this will mean something to someone!
Regrds, Tom
10-05-2009, 02:36 PM
#7
Tech Contributor
I have now tried disconnecting the seat control module but made no difference at all. I have removed the drivers door panel and checked all the wiring and connections and as far as can tell all is fine and have tried disconnecting the door controls e.t.c to no avail.
The problem has, though, started to become intermittent as I have driven it today for a few miles to see what happened.
Every now and then the gauges will return to normal and all the warnings will disappear with exception to the traction control symbol and on some instances the security symbol stays on but reduced engine power e.t.c is gone. In this instance I have managed to run another diagnostics check and the PCM can now be read. The only code it brings up is P1626 (theft deterrent system fuel enable circuit).
Strangely, the illumination on the climate control unit will come on and off as it feels too, even when all the lights are turned off.
The problem seems to be getting more confusing but i'm hoping some of this will mean something to someone!
Regrds, Tom
The problem has, though, started to become intermittent as I have driven it today for a few miles to see what happened.
Every now and then the gauges will return to normal and all the warnings will disappear with exception to the traction control symbol and on some instances the security symbol stays on but reduced engine power e.t.c is gone. In this instance I have managed to run another diagnostics check and the PCM can now be read. The only code it brings up is P1626 (theft deterrent system fuel enable circuit).
Strangely, the illumination on the climate control unit will come on and off as it feels too, even when all the lights are turned off.
The problem seems to be getting more confusing but i'm hoping some of this will mean something to someone!
Regrds, Tom
PM sent.
10-05-2009, 02:51 PM
#8
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I disconnected the door control at the control itself. Should I have disconnected it at the kickpanel to cut out the wiring through the accordian tube?
10-05-2009, 02:55 PM
#9
Tech Contributor
10-05-2009, 03:13 PM
#10
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I have disconnected both plugs at the kick panel on both sides (driver and passenger) and still the problem persists. It seems to be intermittent still, where it will be perfectly fine for a couple minutes and then go back to crazy again with messed up dials and flashing warning messages!
10-05-2009, 03:23 PM
#11
Tech Contributor
I have disconnected both plugs at the kick panel on both sides (driver and passenger) and still the problem persists. It seems to be intermittent still, where it will be perfectly fine for a couple minutes and then go back to crazy again with messed up dials and flashing warning messages!
12-07-2010, 02:30 AM
#12
Drifting
I boneheadedly hyperextended my driver's side door, and now I'm getting this "reduced engine power" and "no comm" error whenever I open it with the car running.
What exactly am I looking for in that harness that goes into the door though? Everything I can see looks fine - do I need to unwrap all the wires to check them or is there some sort of testing I can do with a DMM?
What exactly am I looking for in that harness that goes into the door though? Everything I can see looks fine - do I need to unwrap all the wires to check them or is there some sort of testing I can do with a DMM?
