I have serial data comm problems!!
05-14-2008, 11:44 PM
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I have serial data comm problems!!
Thanks to the good advice from some of the more experienced and most helpful forum users here, I'm starting a new thread regarding my no start issue. The car does not crank but will when the TDR is jumpered.
Here are my current symptoms. I'm tending to think I need to replace my BCM.
When I turn the key, the DIC indicates "Low Fuel", "Check Tire Press.", "Service Tire Mon. Sys.", "Service Vehicle Soon". With the key in the "on" position the following items are WORKING:
fuel release button works, passenger air bag light/switch works, door locks work on both doors, instrument cluster lights work, lights on radio works, fuel release works, HUD works, turn signals work, head lights and motors work - low and high beam, HVAC works, wind shield wipers work, windshield wiper sprayer works, brake lights work, beeping thingy works, mirror controls work, power seats work with all functions, cigarette lighter under radio works, steering wheel telescope works, check engine light on dash is on, check gauges light is on, seat belt light works and goes off when belt is engaged, seat memory buttons work for both settings, rear window defrost works, reverse lights work.
Although the radio lights work, the radio does not, no interior lights, no trunk release, no convertible top storage compartment release, no glove box light, no light under passenger foot well, FOB does not work, windows do not work for both doors, disable active handling not working, cruise control not working, fog lamps not working, and cigarette lighter in arm rest does not work.
When I turn the key, I hear what sounds like the fuel pump running intermittently, but I hear no clicking sounds from the passenger foot well even with floor cover off of the BCM storage compartment.
When I reset the code for the HVAC NO COMM., I hear a thud noise behind the HVAC control panel - sounds like a damper opening or closing?
DIC Codes displayed are:
10 - PCM No Codes
28 - TCS No Codes
40 - BCM No Comm.
58 - SDM 2 Codes
U1000HC Class 2 Communication Malfunction
U1064HC Loss of Communication with BCM
60 - IPC 2 Codes
U1160HC Loss of Communications with LDCM
U1176HC Loss of Communications with RFA
80 - Radio No Codes
99 - HVAC No Comm.
A0 - LDCM No Codes
A1 - RDCM No Codes
B0 - RFA No Codes
Here are my current symptoms. I'm tending to think I need to replace my BCM.
When I turn the key, the DIC indicates "Low Fuel", "Check Tire Press.", "Service Tire Mon. Sys.", "Service Vehicle Soon". With the key in the "on" position the following items are WORKING:
fuel release button works, passenger air bag light/switch works, door locks work on both doors, instrument cluster lights work, lights on radio works, fuel release works, HUD works, turn signals work, head lights and motors work - low and high beam, HVAC works, wind shield wipers work, windshield wiper sprayer works, brake lights work, beeping thingy works, mirror controls work, power seats work with all functions, cigarette lighter under radio works, steering wheel telescope works, check engine light on dash is on, check gauges light is on, seat belt light works and goes off when belt is engaged, seat memory buttons work for both settings, rear window defrost works, reverse lights work.
Although the radio lights work, the radio does not, no interior lights, no trunk release, no convertible top storage compartment release, no glove box light, no light under passenger foot well, FOB does not work, windows do not work for both doors, disable active handling not working, cruise control not working, fog lamps not working, and cigarette lighter in arm rest does not work.
When I turn the key, I hear what sounds like the fuel pump running intermittently, but I hear no clicking sounds from the passenger foot well even with floor cover off of the BCM storage compartment.
When I reset the code for the HVAC NO COMM., I hear a thud noise behind the HVAC control panel - sounds like a damper opening or closing?
DIC Codes displayed are:
10 - PCM No Codes
28 - TCS No Codes
40 - BCM No Comm.
58 - SDM 2 Codes
U1000HC Class 2 Communication Malfunction
U1064HC Loss of Communication with BCM
60 - IPC 2 Codes
U1160HC Loss of Communications with LDCM
U1176HC Loss of Communications with RFA
80 - Radio No Codes
99 - HVAC No Comm.
A0 - LDCM No Codes
A1 - RDCM No Codes
B0 - RFA No Codes
05-15-2008, 01:58 PM
#2
Safety Car
Troubleshooting info for the C5 serial-data-bus : (by ersatz928)
Every module which talks on the serial bus has it own piece of wire which comes to a"star" junction. The star junction is where all the wires connect together, so all the modules can talk to each other. There are actually physically two star junctions, located next to each other, to the left of the BCM module. There are two because GM needed more wire connections than one star junction block could handle, there is a short wire that connects the two star blocks together. Each star is a black (or grey?) rectangular plastic block, with lots of wires on one side. It is really just a multipin connector which is plugged-into a shorting socket, which connects all the wires together.
C5 modules (and the databus wire color) on the serial-bus are :
BCM (Light Green)
PCM (Dark Green)
IPC Instrument Cluster (Gray)
DDM Driver Door Lock Module (also controls the window) (Brown)
PDM Passenger Door Lock Module (also controls the window) (Tan)
Radio (but not the CD Changer) (Orange)
Auto-Climate control head-unit/display (Option) (White)
RCDLR (Radio receiver for the Key-Fob transmitter and Tire Pressure sensors) (Pink)
SCM module for Memory Power Seats and telescope colum (Option) (Brown white stripe)
ESC Electronic suspension shock damping control module (Option) (Dark Blue with white stripe)
EBCM Traction Control/AH module (Light Blue)
SDM (Airbag control) module (Dark Blue)
The Star Bus also has a connection at the Data Link Connector (under the drivers side dash) where you connect a OBD2 code scanner to. DLC pin #2 (Purple wire)
There are three kinds of failures that can take down the whole data-bus :
1) One of the wires is shorted to ground, somewhere along its length between the star junction and the module location.
2) One of the modules has an internal bus-driver/receiver failure which forces a continious positive voltage on the bus.
3) One of the modules has an internal bus-driver/receiver failure which forces a continious low voltage (short to ground) on the bus.
This troubleshooting assumes there is only one shorting problem with the data bus wiring, or one module.
1) Disconnect the battery
2) Use an Ohm-meter (DVM, DMM, VOM..) to measure the resistance between DLC pin #2 (Purple wire, upper row, the pin to the left of the rightmost pin), and to chassis ground DLC pin #4 (Black wire, upper row, fourth pin to the left of rightmost pin). I think the measured resistance should be 5K (5000) Ohms or greater. If it measures at least 5000 ohms, you don’t have a short-to-ground on the data bus. If it is less than 5000 ohms got the next step. NOTE : I need to verify the 5000 Ohm go/nogo resistance.
3) Unplug the 2 BCM connectors. If the low resistance goes to 5000 ohms, the problem is internal to the BCM module, replace it. If the low resistance remains, re-install the BCM connectors and goto the next step.
4) Unplug the shorting socket from both Star connectors. Use your ohmeter to probe one wire at a time, to find the low resistance to ground. Identify the offending bus-wire and/or module by using the wire color associated with each module (see the module list above). 5)Find and unplug the module you identified in step 4. If the low resistance goes away, then that module has an internal short. If the resistance stays low, then the short is in the wire itself, somewhere between the Star block and the module location.
Note : The wire colors are from my 2001 factory service manual, I have not verified that they are the correct colors at the star connector blocks , or if they apply to all model year C5s.
---------------------------------------------------------------------
Other BCM Info
BCM +12V power feeds
Fuse #25 = BCM Logic Power Feed
Fuse #23 +Power feed for 12V BCM Drive outputs (CL)
Fuse #13 = 12V switched from ignition switch (ON, and START positions)
Fuse #9 = 12V from Ignition switch ON and ACC position)
BCM grounds
A9-C1 connector pin Logic Ground
A2-C3 Power Drive Ground
BCM Functions
Traction control switch (sends switch signal to TCM)
Automatic headlamps
Parklamps
Headlamp doors
DRL
Turn signal control
Fog lamp control
Dash light dimming function (HVAC control, console lamp,PRNDL lamp,
Back-up lamp flash when locking/unlocking
Monitored load control (underhood lamp, glove box lamp, vanity mirror lamps, map light)
Interior courtesy lamps
Antitheft horn alarm and TDR (starter cutoff) control
Vehicle Antitheft PassKey circuit
Rear window defogger
Horn
Colum Lock
Hatch release and ajar warnings for (or convertible top cover release)
Key in ignition warning chime
Driver door key unlock signal (disarms antitheft horn alarm)
======================================== =====
I cut/pasted this from another thread as it is EXCELLENT information from ersatz928 ....
frohara .... have you been able to confirm that all the power feeds to the BCM are good ???
Every module which talks on the serial bus has it own piece of wire which comes to a"star" junction. The star junction is where all the wires connect together, so all the modules can talk to each other. There are actually physically two star junctions, located next to each other, to the left of the BCM module. There are two because GM needed more wire connections than one star junction block could handle, there is a short wire that connects the two star blocks together. Each star is a black (or grey?) rectangular plastic block, with lots of wires on one side. It is really just a multipin connector which is plugged-into a shorting socket, which connects all the wires together.
C5 modules (and the databus wire color) on the serial-bus are :
BCM (Light Green)
PCM (Dark Green)
IPC Instrument Cluster (Gray)
DDM Driver Door Lock Module (also controls the window) (Brown)
PDM Passenger Door Lock Module (also controls the window) (Tan)
Radio (but not the CD Changer) (Orange)
Auto-Climate control head-unit/display (Option) (White)
RCDLR (Radio receiver for the Key-Fob transmitter and Tire Pressure sensors) (Pink)
SCM module for Memory Power Seats and telescope colum (Option) (Brown white stripe)
ESC Electronic suspension shock damping control module (Option) (Dark Blue with white stripe)
EBCM Traction Control/AH module (Light Blue)
SDM (Airbag control) module (Dark Blue)
The Star Bus also has a connection at the Data Link Connector (under the drivers side dash) where you connect a OBD2 code scanner to. DLC pin #2 (Purple wire)
There are three kinds of failures that can take down the whole data-bus :
1) One of the wires is shorted to ground, somewhere along its length between the star junction and the module location.
2) One of the modules has an internal bus-driver/receiver failure which forces a continious positive voltage on the bus.
3) One of the modules has an internal bus-driver/receiver failure which forces a continious low voltage (short to ground) on the bus.
This troubleshooting assumes there is only one shorting problem with the data bus wiring, or one module.
1) Disconnect the battery
2) Use an Ohm-meter (DVM, DMM, VOM..) to measure the resistance between DLC pin #2 (Purple wire, upper row, the pin to the left of the rightmost pin), and to chassis ground DLC pin #4 (Black wire, upper row, fourth pin to the left of rightmost pin). I think the measured resistance should be 5K (5000) Ohms or greater. If it measures at least 5000 ohms, you don’t have a short-to-ground on the data bus. If it is less than 5000 ohms got the next step. NOTE : I need to verify the 5000 Ohm go/nogo resistance.
3) Unplug the 2 BCM connectors. If the low resistance goes to 5000 ohms, the problem is internal to the BCM module, replace it. If the low resistance remains, re-install the BCM connectors and goto the next step.
4) Unplug the shorting socket from both Star connectors. Use your ohmeter to probe one wire at a time, to find the low resistance to ground. Identify the offending bus-wire and/or module by using the wire color associated with each module (see the module list above). 5)Find and unplug the module you identified in step 4. If the low resistance goes away, then that module has an internal short. If the resistance stays low, then the short is in the wire itself, somewhere between the Star block and the module location.
Note : The wire colors are from my 2001 factory service manual, I have not verified that they are the correct colors at the star connector blocks , or if they apply to all model year C5s.
---------------------------------------------------------------------
Other BCM Info
BCM +12V power feeds
Fuse #25 = BCM Logic Power Feed
Fuse #23 +Power feed for 12V BCM Drive outputs (CL)
Fuse #13 = 12V switched from ignition switch (ON, and START positions)
Fuse #9 = 12V from Ignition switch ON and ACC position)
BCM grounds
A9-C1 connector pin Logic Ground
A2-C3 Power Drive Ground
BCM Functions
Traction control switch (sends switch signal to TCM)
Automatic headlamps
Parklamps
Headlamp doors
DRL
Turn signal control
Fog lamp control
Dash light dimming function (HVAC control, console lamp,PRNDL lamp,
Back-up lamp flash when locking/unlocking
Monitored load control (underhood lamp, glove box lamp, vanity mirror lamps, map light)
Interior courtesy lamps
Antitheft horn alarm and TDR (starter cutoff) control
Vehicle Antitheft PassKey circuit
Rear window defogger
Horn
Colum Lock
Hatch release and ajar warnings for (or convertible top cover release)
Key in ignition warning chime
Driver door key unlock signal (disarms antitheft horn alarm)
======================================== =====
I cut/pasted this from another thread as it is EXCELLENT information from ersatz928 ....
frohara .... have you been able to confirm that all the power feeds to the BCM are good ???
05-15-2008, 08:50 PM
#3
Melting Slicks
Here's the link to the original thread, in case anyone wants to refer back to it.
http://forums.corvetteforum.com/show....php?t=2007787
Assuming that you have checked, or are going to check the power inputs to the BCM and they are good, have you checked the various modules that can take down the bus.
He's the list that Bill C posted in the other thread.
"When the serial data buss has an issue, I unplug every other module that isnt necessary for the engine to run. Once I get the engine to run normaly, I plug each module back in ONE at a time until the problem reoccurs.
Things that you can unplug are:
RFA
IPC
SCM
Radio
any suspension module F45, F55
LDCM
RDCM
HVAC
EBTCM"
You listed no comm with the HVAC and have codes for the LDCM, and RFA, so I would start with those. Also the SDM module is next to the BCM and could have been affected when the passenger footwell area was flooded.
If it is the BCM, I doubt you will be able to say definatively that it is bad, without trying a new one. The best you will be able to do is narrow down the list of things it's not, and then make your best guess.
http://forums.corvetteforum.com/show....php?t=2007787
Assuming that you have checked, or are going to check the power inputs to the BCM and they are good, have you checked the various modules that can take down the bus.
He's the list that Bill C posted in the other thread.
"When the serial data buss has an issue, I unplug every other module that isnt necessary for the engine to run. Once I get the engine to run normaly, I plug each module back in ONE at a time until the problem reoccurs.
Things that you can unplug are:
RFA
IPC
SCM
Radio
any suspension module F45, F55
LDCM
RDCM
HVAC
EBTCM"
You listed no comm with the HVAC and have codes for the LDCM, and RFA, so I would start with those. Also the SDM module is next to the BCM and could have been affected when the passenger footwell area was flooded.
If it is the BCM, I doubt you will be able to say definatively that it is bad, without trying a new one. The best you will be able to do is narrow down the list of things it's not, and then make your best guess.
Last edited by Greg_E; 05-15-2008 at 09:42 PM.
05-16-2008, 02:34 PM
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I'm pretty sure this is a new problem, but now I am missing voltage at the fuse panel in the pass. compartment. Fuses 2, 9, 10, 11, 13, 14, 16, 18, 19, 22, 26 have no voltage on either side of the fuse.
05-17-2008, 05:25 PM
#8
Safety Car
First, you gotta give us an idea of what you are doing .... you post a question as above listing a whole bunch of fuses that don't have power ... then post you fixed it without giving us any clue what you did .... what are you doing to the car ?????
Second, you need to take an organized approach to diagnosing your problem(s) .....
Your BCM is not communicating with the rest of the car. That should be the NUMBER ONE issue to address .....
This is not a 1962 Chevelle where you can find any electrical problem with a test lamp ..... this is a car that has numerous computers that are networked together to manage and control virtually EVERY electrical function on the car. Heck, the BCM can beep the horn on command from other computers such as the RFA .... you won't figure that out with a test lamp or a DMM.
The BCM controls certain circuits in the car, either directly, or indirectly by "commanding" other computers to perform certain functions. Without the BCM working correctly you may experience all kinds of apparent electrical "gremlins" in the car that will disappear once it is fixed. You can spend fruitless hours trying to trace an "engine start" problem with a DMM when in fact it is a simple "password" from the BCM that the PCM is waiting to see on the communications bus between the computers.
So let's start with the basics .... Is the BCM getting power on all its supply circuits (listed in post #2 above) ???????
Have you inspected the wiring connections at the BCM for water intrusion/corrosion ????
Have you opened up the STAR connectors and limited the number of computers connected to the following 3 ..... PCM, BCM, and IPC ???? If you display codes with that combination does the BCM now respond ... or does it still indicate NO COMM ??????
Please let us know what you find with these tests. Please don't go changing other stuff as you try these ... let's walk before we run ......
Or, if you simply want to post what you're doing .... and are not gonna listen to "advice" from people like Bill Curlee on how to go about tracking down the problem ... just let us know and we'll quit spending time typing stuff you're gonna ignore.
Last edited by BlackZ06; 05-17-2008 at 05:33 PM.
05-18-2008, 08:13 PM
#9
Melting Slicks
Fuse #14 is power to the clutch position switch. With the ignition switch on, you should have power there. I would troubleshoot that. You could bring a fused jumper to the clutch position switch to see if that fixes the problem. If it does, you will need to trace the circuit back, to find out where you lost the power. Did you ever check the ignition switch contacts, or was that the other guy in the previous thread? Have you checked to see if you have power at the BCM from fuse #13 (power to the BCM with switch on or in ACC position). If the ignition switch is bad, perhaps the two problems are related.
Last edited by Greg_E; 05-19-2008 at 05:47 AM.
05-23-2008, 03:08 AM
#11
Safety Car
Apparently he has convinced himself he needs a new BCM ....
http://forums.corvetteforum.com/show...post1565553777
http://forums.corvetteforum.com/show...post1565553777
05-27-2008, 01:56 AM
#12
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I opened the BCM enclosure, and there was a water mark on the circuit board about 2 inches up from the bottom. Yes, I have convinced myself that I need a new BCM.
05-27-2008, 11:45 AM
#13
Safety Car
You post you have a problem .... XXX is happening ....
People post things for you to do to diagnose/fix the problem
* Do A
* Do B
* Try Z
You post back what worked and what didn't work ... and how the problem got fixed.
A few weeks later, if someone searches for problem XXX, they will see what worked for you in diagnosing/fixing the problem.
Your approach (ask a question - provide ZERO feedback) helps no one other than you ..... another user looking at the above thread will learn NOTHING from your posts ... other than you have a problem and you apparently "fixed" it ..... nobody would know you put in a new BCM if I hadn't posted that you were looking for one.
Try providing feedback ... that way everyone's knowledge base expands .... OK ????????
05-31-2008, 11:28 AM
#14
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Did I say that I fixed it? I must have missed that somehow.
Much of my feedback can be found on this thread. I did not get any advise on this thread that I did not already get there. I
I replaced the BCM and the car works now.
Thanks for all the help I recieved. And thanks for the jab too.
http://forums.corvetteforum.com/show....php?t=2007787
Much of my feedback can be found on this thread. I did not get any advise on this thread that I did not already get there. I
I replaced the BCM and the car works now.
Thanks for all the help I recieved. And thanks for the jab too.
http://forums.corvetteforum.com/show....php?t=2007787
05-31-2008, 12:51 PM
#15
Melting Slicks
Good to hear that you got it running. 
Some people have been lucky and just had to clean up the connectors and dry the BCM out. You weren't one of them. The high water mark on the BCM circuit board certainly wasn't wasn't a good sign.
Some people have been lucky and just had to clean up the connectors and dry the BCM out. You weren't one of them. The high water mark on the BCM circuit board certainly wasn't wasn't a good sign.
06-02-2008, 02:46 AM
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Yea, I figured the BCM was shot when I opened it up. Here's what it looked like:
The car starts, everything works and I have no codes, EXCEPT... Pull key and wait 1o seconds, SERVICE COLUMN LOCK.
I've have the dealer "fix" for this once before. Any suggestions? I tried to pull fuses, etc. Do I need a CLB?
The car starts, everything works and I have no codes, EXCEPT... Pull key and wait 1o seconds, SERVICE COLUMN LOCK.
I've have the dealer "fix" for this once before. Any suggestions? I tried to pull fuses, etc. Do I need a CLB?
06-02-2008, 05:57 AM
#17
Melting Slicks
I've read that many people have had problems with the K harness that GM installed as part of the column lock fix, but I'm not sure what the symptom is when it fails. If yours has the white relay in the k harness, it could be a problem. ( I just don't know if it's your problem, so I don't want to send you off in the wrong direction.) I think you can just remove the K harness, to see if it corrects the problem. There are plenty of threads in the archives discussing your exact problem. You should be able to find some info there.
Here's a start:
http://forums.corvetteforum.com/show...=pull+key+wait
Here's a start:
http://forums.corvetteforum.com/show...=pull+key+wait
Last edited by Greg_E; 06-02-2008 at 07:23 PM. Reason: Found a better thread dicussing the problem. Changed link
06-02-2008, 12:53 PM
#18
Melting Slicks
The colum lock problem is probably because the relay which drives it is on the BCM board. It looks like both relays, near the green connector, were underwater. My guess is it got water insided the black plastic relay cover, which corroded the relay guts/contacts. You can try to pop-off the relay cover, and try to clean it up. If it is in bad shape, you could probably unsolder it (4 or 5 connections) and put a new 12V relay in there. Check-out Digikey for a 12VDC SPDT relay which has the same size/pin-out, these things are fairly standard.
06-02-2008, 06:48 PM
#19
Melting Slicks
He has already replaced the BCM. The pull key wait 10 sec. is the only remaining problem at this point.
Assuming you've tried all the easy stuff, like charging the battery, cleaning the key resistor pellet, trying a different key etc., I would try removing the K harness, and see if it fixes the problem. It is well documented that there have been numerous failures. If you don't have the CLB, you should probably get it. Even if it didn't fix the problem, it will be money well spent, to avoid future problems.
If the microswitch in the actuator motor has failed, you will need to find a way to trick the BCM into thinking the actuator motor is in the unlocked position. Check the new link I added to my previous post.It has good info regarding the problems I've listed here.
Assuming you've tried all the easy stuff, like charging the battery, cleaning the key resistor pellet, trying a different key etc., I would try removing the K harness, and see if it fixes the problem. It is well documented that there have been numerous failures. If you don't have the CLB, you should probably get it. Even if it didn't fix the problem, it will be money well spent, to avoid future problems.
If the microswitch in the actuator motor has failed, you will need to find a way to trick the BCM into thinking the actuator motor is in the unlocked position. Check the new link I added to my previous post.It has good info regarding the problems I've listed here.
Last edited by Greg_E; 06-02-2008 at 07:38 PM.
06-20-2008, 02:01 PM
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I purchase the CLB from Corvetttes of Houston, installed it in less than 5 minutes, and everything works great!
I did have a problem with the battery going dead when I left the car for more than a couple of hours. I dealt with that by disconnecting the battery each time I parked it.
Finally got some time to troubleshoot, and I think I narrowed it down to the mini relay controlling the rear defrost. Apparently this relay got corroded when I had about 3 inches of water on the passenger side floor board (this is what fried the BCM also) and either got stuck closed, or had a short across the contacts. I removed the relay and no more dead battery problem! I'm going to replace the relay as soon as I get a chance to visit the dealer.
I thought I was good to go, but I just discovered that I’m not completely in the clear. When I replaced the BCM, I did not get it reprogrammed. I performed the relearn procedure and thought that was good enough. Today I was trying to get the horn to chirp when I use the key fob to lock the car, but couldn’t find that option on the display on the ICP. I couldn’t find any configuration options for the twilight sentinel either. I don’t know what else is missing, but it seems like there was a lot more stuff I could configure before. Is this due to my replacing the BCM and not getting it reprogrammed? Can I reprogram the BCM myself using an Actron Autoscanner Plus CP9180 or do I need to have the dealer perform the proceedure for $90?
I did have a problem with the battery going dead when I left the car for more than a couple of hours. I dealt with that by disconnecting the battery each time I parked it.
Finally got some time to troubleshoot, and I think I narrowed it down to the mini relay controlling the rear defrost. Apparently this relay got corroded when I had about 3 inches of water on the passenger side floor board (this is what fried the BCM also) and either got stuck closed, or had a short across the contacts. I removed the relay and no more dead battery problem! I'm going to replace the relay as soon as I get a chance to visit the dealer.
I thought I was good to go, but I just discovered that I’m not completely in the clear. When I replaced the BCM, I did not get it reprogrammed. I performed the relearn procedure and thought that was good enough. Today I was trying to get the horn to chirp when I use the key fob to lock the car, but couldn’t find that option on the display on the ICP. I couldn’t find any configuration options for the twilight sentinel either. I don’t know what else is missing, but it seems like there was a lot more stuff I could configure before. Is this due to my replacing the BCM and not getting it reprogrammed? Can I reprogram the BCM myself using an Actron Autoscanner Plus CP9180 or do I need to have the dealer perform the proceedure for $90?