Code U0100 Question
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TECH Junkie
Joined: Dec 2005
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Code U0100 Question I have installed an L92/6l80 into my 1965 Buick Skylark. The motor came out of a 2008 Escalade. Not sure of the transmission.
Using an E38 PCM.
I am getting on my scanner a U0100 code which is "lost communication with ECM/PCM A". I have been doing some checking with the wiring and have come up with nothing. I assume the scanner is communicating with the transmission control module as there are no codes for it.
Now I do get codes every such as lean condition on left and right back O2 sensors so not all it dead. I just cannot clear the U0100 code. Would the transmission module have something to do with it if it was not exactly compatable? Just looking for some answers.
Using an E38 PCM.
I am getting on my scanner a U0100 code which is "lost communication with ECM/PCM A". I have been doing some checking with the wiring and have come up with nothing. I assume the scanner is communicating with the transmission control module as there are no codes for it.
Now I do get codes every such as lean condition on left and right back O2 sensors so not all it dead. I just cannot clear the U0100 code. Would the transmission module have something to do with it if it was not exactly compatable? Just looking for some answers.
Does the engine start? Can you datalog the ECM for basic stuff like RPM, timing, MAP, etc?
If not, either the ECM is bad or the communication is lost. It is possible that you are scanning the TCM thru the CAN network but the ECM is not present.
If you can't scan the ECM or read the tune, then the problem is with the ECM.
Gen4 stuff have 2 communication networks. The class-2 serial data used for IPC, OBD-II, radio and several other modules.
There is a high speed GMlan network. It handless the comms for high priority tasks. The network starts at the ECM, then goes to the TCM, BCM, ABS, etc. It uses a twisted pair of wires and 2 network terminators.
If you used only the ECM and TCM and deleted BCM and all other stuff, you need to put a 120 ohm resistor at the DLC connector to complete the network ECM-TCM-DLC
If not, either the ECM is bad or the communication is lost. It is possible that you are scanning the TCM thru the CAN network but the ECM is not present.
If you can't scan the ECM or read the tune, then the problem is with the ECM.
Gen4 stuff have 2 communication networks. The class-2 serial data used for IPC, OBD-II, radio and several other modules.
There is a high speed GMlan network. It handless the comms for high priority tasks. The network starts at the ECM, then goes to the TCM, BCM, ABS, etc. It uses a twisted pair of wires and 2 network terminators.
If you used only the ECM and TCM and deleted BCM and all other stuff, you need to put a 120 ohm resistor at the DLC connector to complete the network ECM-TCM-DLC
Thread Starter
TECH Junkie
Joined: Dec 2005
Posts: 3,092
Likes: 11
Does the engine start? Can you datalog the ECM for basic stuff like RPM, timing, MAP, etc?
If not, either the ECM is bad or the communication is lost. It is possible that you are scanning the TCM thru the CAN network but the ECM is not present.
If you can't scan the ECM or read the tune, then the problem is with the ECM.
Gen4 stuff have 2 communication networks. The class-2 serial data used for IPC, OBD-II, radio and several other modules.
There is a high speed GMlan network. It handless the comms for high priority tasks. The network starts at the ECM, then goes to the TCM, BCM, ABS, etc. It uses a twisted pair of wires and 2 network terminators.
If you used only the ECM and TCM and deleted BCM and all other stuff, you need to put a 120 ohm resistor at the DLC connector to complete the network ECM-TCM-DLC
If not, either the ECM is bad or the communication is lost. It is possible that you are scanning the TCM thru the CAN network but the ECM is not present.
If you can't scan the ECM or read the tune, then the problem is with the ECM.
Gen4 stuff have 2 communication networks. The class-2 serial data used for IPC, OBD-II, radio and several other modules.
There is a high speed GMlan network. It handless the comms for high priority tasks. The network starts at the ECM, then goes to the TCM, BCM, ABS, etc. It uses a twisted pair of wires and 2 network terminators.
If you used only the ECM and TCM and deleted BCM and all other stuff, you need to put a 120 ohm resistor at the DLC connector to complete the network ECM-TCM-DLC
I disconnected the X1 connector at the ECM and across the pins I read 120 ohms which would be correct with only the one resistor in the circuit at the TCM. Running the factory harness which has been somewhat modified with wires deleted such as the rear O2 connectors.
Last edited by 1989GTA; Jun 23, 2013 at 11:25 AM.
Cut power to the TCM and start the engine. Scan it again to see if the code is still present.
I have 2 E38 PCMs from 5.3L Silverados and they both have the U0100 code set to 3-no report which makes sense.
I have 2 E38 PCMs from 5.3L Silverados and they both have the U0100 code set to 3-no report which makes sense.
Thread Starter
TECH Junkie
Joined: Dec 2005
Posts: 3,092
Likes: 11
So maybe I can get the ECM/PCM tuned along with maybe the Corvette "tune" for the 6L80?
Edit: Forgot to say there appears to be no U0100 code with the TCM fuse pulled.
Last edited by 1989GTA; Jun 23, 2013 at 01:18 PM.
Is normal for the SES light to stay ON when engine is not running, it's part of OBD-II standards.
If the code went away with the fuse pulled, you may have some operating system incompatibility between ECM and TCM, check part numbers to see if you aren't mixing different years. Sometimes flashing a complete tune to both can fix issues like this. Ssometimes the TCM is not compatible with the new OS and it makes things worse or even brick the TCM.
The best way to flash a complete OS for both ECM and TCM is to take it to the dealer, there are parts of those controllers which can't be written using tuning software.
If the code went away with the fuse pulled, you may have some operating system incompatibility between ECM and TCM, check part numbers to see if you aren't mixing different years. Sometimes flashing a complete tune to both can fix issues like this. Ssometimes the TCM is not compatible with the new OS and it makes things worse or even brick the TCM.
The best way to flash a complete OS for both ECM and TCM is to take it to the dealer, there are parts of those controllers which can't be written using tuning software.
Thread Starter
TECH Junkie
Joined: Dec 2005
Posts: 3,092
Likes: 11
Is normal for the SES light to stay ON when engine is not running, it's part of OBD-II standards.
If the code went away with the fuse pulled, you may have some operating system incompatibility between ECM and TCM, check part numbers to see if you aren't mixing different years. Sometimes flashing a complete tune to both can fix issues like this. Ssometimes the TCM is not compatible with the new OS and it makes things worse or even brick the TCM.
The best way to flash a complete OS for both ECM and TCM is to take it to the dealer, there are parts of those controllers which can't be written using tuning software.
If the code went away with the fuse pulled, you may have some operating system incompatibility between ECM and TCM, check part numbers to see if you aren't mixing different years. Sometimes flashing a complete tune to both can fix issues like this. Ssometimes the TCM is not compatible with the new OS and it makes things worse or even brick the TCM.
The best way to flash a complete OS for both ECM and TCM is to take it to the dealer, there are parts of those controllers which can't be written using tuning software.
I think what I will have to do is get the ECM "tuned" so the motor will run decent enough to drive. Then make a decision on what to do about the TCM. Seeing it is buried in the transmission that makes things a little harder.
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Teching In
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Does the engine start? Can you datalog the ECM for basic stuff like RPM, timing, MAP, etc?
If not, either the ECM is bad or the communication is lost. It is possible that you are scanning the TCM thru the CAN network but the ECM is not present.
If you can't scan the ECM or read the tune, then the problem is with the ECM.
Gen4 stuff have 2 communication networks. The class-2 serial data used for IPC, OBD-II, radio and several other modules.
There is a high speed GMlan network. It handless the comms for high priority tasks. The network starts at the ECM, then goes to the TCM, BCM, ABS, etc. It uses a twisted pair of wires and 2 network terminators.
If you used only the ECM and TCM and deleted BCM and all other stuff, you need to put a 120 ohm resistor at the DLC connector to complete the network ECM-TCM-DLC
If not, either the ECM is bad or the communication is lost. It is possible that you are scanning the TCM thru the CAN network but the ECM is not present.
If you can't scan the ECM or read the tune, then the problem is with the ECM.
Gen4 stuff have 2 communication networks. The class-2 serial data used for IPC, OBD-II, radio and several other modules.
There is a high speed GMlan network. It handless the comms for high priority tasks. The network starts at the ECM, then goes to the TCM, BCM, ABS, etc. It uses a twisted pair of wires and 2 network terminators.
If you used only the ECM and TCM and deleted BCM and all other stuff, you need to put a 120 ohm resistor at the DLC connector to complete the network ECM-TCM-DLC
Hey Montecarlo,
Re your comment in a post... https://ls1tech.com/forums/pcm-diagn...-question.html
I am also having U0100 issues on a new LS swap.
"Gen4 stuff have 2 communication networks. The class-2 serial data used for IPC, OBD-II, radio and several other modules.
There is a high speed GMlan network. It handless the comms for high priority tasks. The network starts at the ECM, then goes to the TCM, BCM, ABS, etc. It uses a twisted pair of wires and 2 network terminators. If you used only the ECM and TCM and deleted BCM and all other stuff, you need to put a 120 ohm resistor at the DLC connector to complete the network ECM-TCM-DLC"
Any chance of a wiring diagram on how to hook up the resistor to the DLC? Does it go on the + or - Can line etc?
Thanks
Craig
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