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Discussion Starter · #1 ·
Hello and greetings from Norway.

This topic has for sure been up before and I think I have read everyone ever written.

I got a low milage 2006mod Z06.
This winter I did a big job on it. Changing clutch, radiator, water hoses, all fluids, brake pads, steering wheel, quick shift etc etc...
The car has bee out of 12v power for a long time and I know that this is not a good thing. Replaced battery and I have changed the underhood fuse/relay box cause of a broken lock.

The problem is that the car will not start. When hitting to cranck the dash goes black and the engine symbol appears, and after some seconds the acc turns back on and the keylock symbol is on.
It will go to acc and all of the gauges flip over once and everything seems fine. But the keylock stays on..
The doors and anti theft systems seems ok as well with doors opening and locking correctly.
The fobs are detected and no problems there either.
Tried to change the bcm and have done a check on all of the cables. Nothing helped and the new used bcm gave just even more problems.
I have a obd2 scanner and I am just able to get connection with some of the parts in the car. Not the bcm or ecm etc..

I have ordered a Tech2 obd2 diagnostic scanner among with TIS2000, which is a Windows XP based reprogramming tool for laptops.

I think that there must be one out of three options for that the car does not start.

1. The keylock or immobilizer/theft deterrent system is not properly unlocked
2. A 5v or similar +voltage is damaged like a bad cable etc..

My question is:
Has anyone any idea or clue or even had this kind of problem?

I am grateful to any answear. Many thanks.
3. A ground point is bad.

2 and 3 is not so thinkable since I have tested all of the cables that have been "moved" or disconnected.
 

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1. I would do a battery load test to make sure the new battery does not have bad cell(s)
2. Make sure the battery cable connectors are not bad, was a GM TSB about this for the C6s
3. On left outside corner of the engine fuse panel is a main voltage wire, test to see if voltage there and connection is good
4. Make sure on left head, at the back there is a main ground wire to the frame is attached and tight
5. When opening the drivers door the security light on dash flashes, if it does not then the BCM /PCM is not exchanging the security seed code and if changing either of them then the PCM/BCM relearn process has to be done
6. Maybe swap relays around and see if one is not a problem
7. Check for error codes, if so what are they and if they are H (history) or C (current)
8. Make sure the clutch pedal start switch is good and wires to it OK
9. Where the BCM is located in the floor is the car's network, make sure all wiring connectors from connectors are fully connected
 

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Discussion Starter · #3 ·
1. I would do a battery load test to make sure the new battery does not have bad cell(s)
2. Make sure the battery cable connectors are not bad, was a GM TSB about this for the C6s
3. On left outside corner of the engine fuse panel is a main voltage wire, test to see if voltage there and connection is good
4. Make sure on left head, at the back there is a main ground wire to the frame is attached and tight
5. When opening the drivers door the security light on dash flashes, if it does not then the BCM /PCM is not exchanging the security seed code and if changing either of them then the PCM/BCM relearn process has to be done
6. Maybe swap relays around and see if one is not a problem
7. Check for error codes, if so what are they and if they are H (history) or C (current)
8. Make sure the clutch pedal start switch is good and wires to it OK
9. Where the BCM is located in the floor is the car's network, make sure all wiring connectors from connectors are fully connected
Many thanks.
I have done mostly of these points and checked them.
The code that is very bad is U1000. And the diagnostic tool has no connection with bcm or ecm.
But you do mention a couple of points worth checking. So again thanks for your reply.
 

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U cods are comm code saying an issue with a controller or
the car has 2 CAN networks a low and high speed and not talking over the network

Being you swapped the BCM and same problems exists then you know it is not the problem
The DLC you plug your scanner into connects to the PCM

You would know if the PCM and PCM can talk to each other as when drivers door opened the security light on dash should be flashing
IF stays on, then the two are not exchanging the security key or the 2 do not match with same code

To check the PCM you need to take off the lower inner fender well panel on the right front where the PCM and main wiring harness is
Check to see all wiring and connectors to PCM are fine, check if animal have eaten wires

Check all fuses for both PCM and BCM

Assure networks which is by BCM in passenger floor, wiring good, all connectors firmly plugged in

The ignition switch position requires serial data communication to occur, then at least one operating parameter has not been associated with an identification number within 5 seconds after beginning serial data communication (a default value is used)
 

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Discussion Starter · #5 ·
Hi again and many thanks for great suggestions on finding the cause of this.

The security lock sign in dash is not lit at all until the acc is on.
That will be a problem then?

And I am not sure of the ground wire that is going from the rear of left head to the frame? Have I gotten the understanding of that one?
 

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As I mentioned if the PCM and BCM are talking on the CAN network then when the door is opened then
security light on the dash flashes to tell you the 2 controllers agreed on the security seed code.
You're going to have to start doing the suggestions I posted above to zoom into the area that is at fault

There has to be a ground wire from the frame to the engine block so if need be check the frame on both sides and then follow the ground wire to the engine and assure bolted down correctly
 

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Discussion Starter · #7 ·
As I mentioned if the PCM and BCM are talking on the CAN network then when the door is opened then
security light on the dash flashes to tell you the 2 controllers agreed on the security seed code.
You're going to have to start doing the suggestions I posted above to zoom into the area that is at fault

There has to be a ground wire from the frame to the engine block so if need be check the frame on both sides and then follow the ground wire to the engine and assure bolted down correctly
Yes I see. I am getting a guy here with a tech2 to have look as well.
If the bcm and pcm (ecm?) Is not talking to each other then it can be caused by the theft deterrent system? If the 4 antennas is not giving proper info then the bcm and pcm will not be connected and a non starting signal from the rcdlr module. Wich also gives a starting signal when things are ok. Have I figured out this correctly?😅

I found the ground point. It is located just beneath the third spark plug from front. It looks good.
 

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IF the PCM (Powertrain Control Module) and the BCM (Body Control Module) are not talking on the CAN network then of course they cannot crosscheck each other to see if the security seed match correctly then starting the engine would not be allowed
The 4 Ant which is for the controller for the key FOB and tire pressure sensors are not part of PCM/BCM crosschecking the security key code.

The fact the security light on dash is not correctly flashing when door is open or even staying hard on says some issue preventing controllers to talk on network correctly

IF U (comm) codes keep tripping then as long as the car's network is not getting data from controllers they cannot function without proper exchanging information on networks (CAN)

Again you need to get to the PCM, check all wiring there and the wiring connectors, all fuses to PCM & BCM are not shorted out.

IF you can get it where the security light at least stays hard on, then a PCM/BCM relearn could be done and get the 2 controllers re-syncing the security seed code.

If it flashes when the door is open then that says the problem has been fixed

I could assume there also could be a problem with the ign switch, or it's wiring
 

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Discussion Starter · #9 ·
IF the PCM (Powertrain Control Module) and the BCM (Body Control Module) are not talking on the CAN network then of course they cannot crosscheck each other to see if the security seed match correctly then starting the engine would not be allowed
The 4 Ant which is for the controller for the key FOB and tire pressure sensors are not part of PCM/BCM crosschecking the security key code.

The fact the security light on dash is not correctly flashing when door is open or even staying hard on says some issue preventing controllers to talk on network correctly

IF U (comm) codes keep tripping then as long as the car's network is not getting data from controllers they cannot function without proper exchanging information on networks (CAN)

Again you need to get to the PCM, check all wiring there and the wiring connectors, all fuses to PCM & BCM are not shorted out.

IF you can get it where the security light at least stays hard on, then a PCM/BCM relearn could be done and get the 2 controllers re-syncing the security seed code.

If it flashes when the door is open then that says the problem has been fixed

I could assume there also could be a problem with the ign switch, or it's wiring
Good points again. Thanks. I will look into those.
I had the tech2 guy here. Is in partnership of a workshop that does GM.
We got U2105, U2108 and U2100 codes. We did not get any codes on the security system.
One step further👍
 

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Your tech guy if owning a GM tech-II should know what the DTCs mean and react to them

U2100 - GM

TypeNetwork - Manufacturer Controlled DTC - Manufacturer Controlled
DescriptionCAN Bus Off Conditions
CauseKey on and the TCM detected a loss of communication on either Communication Area Network (CAN) Bus line for one second

U2105 - GM

TypeNetwork - Manufacturer Controlled DTC - Manufacturer Controlled
DescriptionCAN Bus Error ECM
CauseKey on and the TCM did not receive ECM messages for 1 second

U2108 - GM

TypeNetwork - Manufacturer Controlled DTC - Manufacturer Controlled
DescriptionCAN Bus Error ABS Conditions
CauseKey on and TCM did not receive EBTCM messages for 1 second

All 3 DTCs point to what I have been saying is a CAN network bus problems
as you see the U 2105 is saying cannot see the ECM (PCM) so never will it start

Someone needs to get into the area where BCM is and make sure all the wiring and connectors are not

cut, eaten by animals, connectors rusted up, etc
and then also get to the PCM and check the same thing there
 

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Discussion Starter · #11 ·
Your tech guy if owning a GM tech-II should know what the DTCs mean and react to them

U2100 - GM

TypeNetwork - Manufacturer Controlled DTC - Manufacturer Controlled
DescriptionCAN Bus Off Conditions
CauseKey on and the TCM detected a loss of communication on either Communication Area Network (CAN) Bus line for one second

U2105 - GM

TypeNetwork - Manufacturer Controlled DTC - Manufacturer Controlled
DescriptionCAN Bus Error ECM
CauseKey on and the TCM did not receive ECM messages for 1 second

U2108 - GM

TypeNetwork - Manufacturer Controlled DTC - Manufacturer Controlled
DescriptionCAN Bus Error ABS Conditions
CauseKey on and TCM did not receive EBTCM messages for 1 second

All 3 DTCs point to what I have been saying is a CAN network bus problems
as you see the U 2105 is saying cannot see the ECM (PCM) so never will it start

Someone needs to get into the area where BCM is and make sure all the wiring and connectors are not

cut, eaten by animals, connectors rusted up, etc
and then also get to the PCM and check the same thing there
Yes he knows. But he had to get the info online at his work. Thanks again.
Yes I will start working on it tomorrow. Very nice of you to help me out👍
 

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Discussion Starter · #12 ·
Today I managed to find the tan and tan/black canbus cables. They are all ok. Also the connectors are ok from bcm to pcm and so on.
Also the canbus cables from the pcm to the ebc is all good.
I will continue tomorrow and check from pcm to the fusebox in the engine bay.
There is no signs of bad cables at all. Everything looks good and original.
Also the groundpoints seems to be ok.

I am going to do even more checks on the wires tomorrow.
 

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Rectangle Schematic Font Parallel Slope

You need to assure also that the ground splice packs are good and clean, check SP200, you would have to pry it apart to check all ground pins
You have not mentioned if you check the 2 fuses for the PCM and 3 fuses for the BCM

Keep in mind the Starbus (CAN ) is controllers are in series so any controller wacked would open the network and now other controllers are out of the network
Also, 1 DTC U code is complaining the EBTCM (ABS) is not talking
Rectangle Font Parallel Slope Number


Rectangle Parallel Font Slope Number

Font Parallel Rectangle Slope Magenta

Rectangle Font Parallel Slope Number


Font Rectangle Parallel Number Screenshot
 

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DTC U2100
Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors
DTC U0073: Controller Area Network (CAN) Bus Communication
DTC U2100: Controller Area Network (CAN) Bus Communication

Circuit Description
The GMLAN serial data circuits are controller area network (CAN) high and/or low speed serial data buses used to communicate information between the control modules.
Typical data transmission speeds must be high enough to ensure that a required real-time response is maintained. There are two different types of GMLAN serial data circuits, the High speed 2-wire circuit and Low speed single wire circuit. The GMLAN serial data circuits also communicate directly to the data link connector (DLC).
Messages are interpreted by the externally connected CANdi module which acts as a transceiver for the scan tool.

Modules connected to the GMLAN serial data circuits monitor communications during normal vehicle operation, where operation information is exchanged among the modules.
All the modules on the GMLAN networks, maintain a transmit error counter (TEC) and a receive error counter (REC). The counter values increase with detected errors and will decrease with error-free messages.

Conditions for Running the DTC
• Supply voltage to the modules are in the normal operating range.
• The vehicle is in the RUN power mode.

Conditions for Setting the DTC
The module setting the DTC has attempted to establish communications on the GMLAN circuits for more than 7 times.

Action Taken When the DTC Sets
• The module suspends all message transmission.
• The module uses default values for all parameters received on the serial data circuits.
• The module inhibits the setting of all other communication DTCs.

Conditions for Clearing the DTC
• A current DTC clears when the malfunction is no longer present.
• A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids
This DTC cannot be retrieved with a current status. Diagnosis of a current DTC is accomplished via Scan Tool Does Not Communicate with High Speed GMLAN Device .
Refer to Data Link References for the correct procedure for the specific module(s) and the busses they use to communicate.

The GM LAN connects the VCIM (OnStar module), the BCM, the ECM, the ESC and the Automatic Transmission Module. The BCM is the bus master. Here is a copy of the schematic for the manual transmission version.

Product Font Slope Rectangle Parallel
 

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Great information for you here! Thanks Racingvette and good luck Larsen. I am following this thread for the education!
 

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Discussion Starter · #17 ·
View attachment 17778
You need to assure also that the ground splice packs are good and clean, check SP200, you would have to pry it apart to check all ground pins
You have not mentioned if you check the 2 fuses for the PCM and 3 fuses for the BCM

Keep in mind the Starbus (CAN ) is controllers are in series so any controller wacked would open the network and now other controllers are out of the network
Also, 1 DTC U code is complaining the EBTCM (ABS) is not talking
View attachment 17774

View attachment 17776
View attachment 17775
View attachment 17774

View attachment 17777
 

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Discussion Starter · #18 ·
I am working on this now. I will update as I go along. The fuses have been checked all the time so no one has been broken so far.
 

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So if you read what I posted above
1 wire is the CAN low speed network
2 wires is the GMLAN high speed network

As the image I posted,
You're looking at the Tan and Tan/Black wires of GMLAN
you notice as I mentioned this is a Starbus network and the controllers are in series so any break or issue opens up the network and that kills off controllers talking
Considering 2 of the DTCs are the PCM and EBTCM you could use an OHM meter and test like at the tan wire pin 27 of the PCM X1 connector and other side of the meter to pin 20 of connector to BCM
Do the same for tan/black if that OHMs out correct that tells you the whole path including the VCIM (Onstar controller) BTW no one just yanked that did they ? As that would open the GMLAN network open)
If I recall correctly, the VCIM is mounting in the right rear of C6s


So again PCM and EBTCM had U error codes, the BCM is the boss and router to all controllers
This schematic gives you everything as color of wires, connector and pins numbers

Product Rectangle Slope Font Schematic
 

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Discussion Starter · #20 ·
Yes. I am working on it. I did ohm out the 2501 and 2500 wires. From bcm and pcm to the obd2 connector. and they are ok. But I will try it one more time like you say.
About the VCIM. It is a 12voltage device right? So I am thinking if it has no power (12v) or ground.. It might be the cause? And I am unsure of if the ground is to the chassis or to the bcm f.ex...?
 
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