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HOMESERVICE MANUALSCHEVROLET2006COBALT SS, 4D SEDAN, STANDARDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 731 (CONTINUOUSLY VARIABLE TRANSMISSION (CVT))DTC TROUBLESHOOTINGDTC U0029: F-CAN MALFUNCTION (BUS-OFF); DTC U0121: F-CAN MALFUNCTION (POWERTRAIN CONTROL MODULE (PCM)-ABS); DTC U0122: F-CAN MALFUNCTION (POWERTRAIN CONTROL MODULE (PCM)-VSA); DTC U0155: F-CAN MALFUNCTION (POWERTRAIN CONTROL MODULE (PCM)-GAUGE CONTROL MODULE); DTC U1205: IMA-CAN MALFUNCTION (POWERTRAIN CONTROL MODULE (PCM)-MOTOR CONTROL MODULE (MCM))
2006 Chevrolet Cobalt SS, 4D Sedan, Standard

DTC U0029: F-CAN Malfunction (BUS-OFF); DTC U0121: F-CAN Malfunction (Powertrain Control Module (PCM)-ABS); DTC U0122: F-CAN Malfunction (Powertrain Control Module (PCM)-VSA); DTC U0155: F-CAN Malfunction (Powertrain Control Module (PCM)-Gauge Control Module); DTC U1205: IMA-CAN Malfunction (Powertrain Control Module (PCM)-Motor Control Module (MCM))

2006 Chevrolet Cobalt SS, 4D Sedan, StandardSECTION DTC U0029: F-CAN Malfunction (BUS-OFF); DTC U0121: F-CAN Malfunction (Powertrain Control Module (PCM)-ABS); DTC U0122: F-CAN Malfunction (Powertrain Control Module (PCM)-VSA); DTC U0155: F-CAN Malfunction (Powertrain Control Module (PCM)-Gauge Control Module); DTC U1205: IMA-CAN Malfunction (Powertrain Control Module (PCM)-Motor Control Module (MCM))
WARNING: This page is about a different car, the 2011 Honda Insight and 2010 Honda Insight. However, it is still accessible from the selected car via links, so may be relevant.

2010 Model 

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot with the HDS, and review General Troubleshooting Information (see GENERAL TROUBLESHOOTING INFORMATION  ).
  1. Turn the ignition switch to ON (II).
  2. Clear the DTC with the HDS.
  3. Check for Pending or Confirmed DTCs in the PGM-FI SYSTEM with the HDS.

    Is DTC U0029, U0121, U0122, U0155, or U1205 indicated in the PGM-FI system? 

    YES  -Go to the DTC U0029 troubleshooting (see DTC U0029: F-CAN MALFUNCTION (BUS-OFF (PCM)) ), DTC U0121 troubleshooting (see DTC U0121: F-CAN MALFUNCTION (PCM-ABS MODULATOR-CONTROL UNIT) ), DTC U0122 troubleshooting (see DTC U0122: F-CAN MALFUNCTION (PCM-VSA MODULATOR-CONTROL UNIT) ), DTC U0155 troubleshooting (see DTC U0155: F-CAN MALFUNCTION (PCM-GAUGE CONTROL MODULE) ), or DTC U1205 troubleshooting (see DTC U0037: IMA-CAN MALFUNCTION (BUS-OFF); DTC U1205: IMA-CAN MALFUNCTION (PCM-MOTOR CONTROL MODULE (MCM)) ).

    NO  -Go to step 4.

  4. Check for Pending or Confirmed DTCs in the A/T SYSTEM with the HDS.

    Is DTC U0029, U0121, U0122, U0155, or U1205 indicated in the A/T system? 

    YES  -Go to step 5.

    NO  -Intermittent failure, the system is OK at this time. If any other Pending or Confirmed DTCs were indicated, go to the indicated DTC's troubleshooting.

  5. Update the PCM if it does not have the latest software (see PCM UPDATE ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ).
  6. Start the engine, and let it idle for at least 2 minutes.
  7. Check for Pending or Confirmed DTCs the A/T SYSTEM with the HDS.

    Is DTC U0029, U0121, U0122, U0155, or U1205 indicated in the A/T system? 

    YES  -Check for poor connections or loose terminals at the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then go to step  6. If the PCM was substituted, go to step  1.

    NO  -Go to step 8.

  8. Monitor the OBD STATUS for U0029, U0121, U0122, U0155, or U1205 in the DTCs MENU with the HDS.

    Does the HDS indicate PASSED? 

    YES  -If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ). If any other Pending or Confirmed DTCs were indicated in step 7, go to the indicated DTC's troubleshooting.

    NO  -If the HDS indicates FAILED, check for poor connections or loose terminals at the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then go to step  1. If the HDS indicates NOT COMPLETED, go to step  6.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.