U0100-Lost Communication with Powertrain Control Module (PCM)

U0100 Lost Communication with Powertrain Control Module (PCM) - Bus messages not received from the Powertrain Control Module (PCM) for approximately two five seconds.

U0100-Lost Communication with ECMPCM


When monitored U0100 code

  • With the ignition on.
  • Battery voltage between 10 and 16 Volts.
  • Ignition Off Draw (IOD) fused installed.
  • Totally Integrated Power Module (TIPM) / Body Control Module (BCM) is configured correctly.

Possible causes:
  • CAN C Bus (+) circuit shorted to voltage.
  • CAN C Bus (-) circuit shorted to ground.
  • DTC related to Battery voltage, ignition, or VIN messages.
  • TIPM/BCM not configured correctly.
  • PCM power and ground.
  • Powertrain Control Module (PCM).
  • Module that set this DTC

Diagnose U0100-Lost Communication with Powertrain Control Module (PCM)


Step 1. Verify the diagnostic trouble code (DTC) is active
Make sure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding. With the scan tool, read active DTC.

Is this DTC active ?

Yes, go to step 2.
No, refer to Sitemap/Labels-Non DTC Diagnostic (Communication) and perform to the Stored Lost Communication.

Step 2. Check for any of the following active DTC
With the scan tool, read all active DTC from all modules. Check for TIPM/BCM configuration, CAN C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTC.

Does the scan tool dispaly any active DTC to the conditions listed above ?

Yes, go to and perform the appropriate diagnostic.
No, go to step 3.

Step 3. Verfiy the PCM is active on the Bus
Turn the ignition on, with the scan tool, view all modules, verfiy the PCM is active on the Bus.

Is the PCM active on the Bus ?

Yes, go to step 4.
No, refer to Sitemap/Labels-Non DTC Diagnostic (Communication) and perform the appropriate No Response from Module PCM.

Step 4. Check for additional communication related DTC
With the scan tool, view all modules.

Is there more than one module with active DTC ''Logged Against'' the PCM ?

Yes, replace and program the Powertrain Control Module (PCM). Perform the Powertrain Verification Test. 
No, go to step 5.

Step 5. Clear DTC in Module setting fault
With the scan tool, select the module setting the DTC against the PCM. Clear active DTC.

Is this DTC still active ?

Yes, replace/Update the Module that set this DTC. Perform the appropriate verification test for the module being replaced. If there is no verification test for the associated module perform the Body Verification Test.
No, go to step 6.

Step 6. Cycle ignition
Cycle the ignition from RUN to OFF three times ending with the key in the RUN position.

Does the DTC become active ?

Yes, go to step 7
No, the condition is not present at this time. Using the wiring diagram as a guide, inspect the wiring for chafed, pierced, pinched, and partially broken wires and wiring harness connectors for broken, bent, pushed out, and corroded terminals.

Step 7. Check for additional Lost Communication Faults
With the scan tool, view all modules.

Does the TIPM/BCM and other CAN C Bus modules show any Lost Communication DTC with remaining CAN C Bus modules ?

Yes, go to step 8.
No, replace/update the module that set this DTC. Perform the appropriate verification test the module being replaced. If there is no verification test for the associated module perform the Body Verification Test.

Step 8. CAN C Bus (+) circuit shorted to voltage
Measure the voltage between the CAN C Bus (+) circuit and the ground.

Is the voltage above 5.0 Volts ?

Yes, repair the short to voltage in the CAN C Bus (+) circuit.
No, go to step 9.

Step 9. CAN C Bus (-) circuit shorted to ground
Turn the ignition off, measure the resistance between ground and the CAN C Bus (-) circuit.

Is the resistance below 10k ohms ?

Yes, repair the short to ground in the CAN C Bus (-) circuit.
No, replace/update the module that set this DTC. Perform the appropriate verification test for the module being replaced. If there is no verification test for the associated module perform the Body Verification Test.

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