C1201 – Engine Control System Malfunction


When the Electronic Control Unit (ECU) has failed, the C1201 happens
The C1201 is triggered when the Electronic Control Unit (ECU) has failed

The Electronic Control Unit (ECU) has failed.

Main Symptoms:

  • Check Engine Light comes on
  • Other warning lights may come on depending on which module is affected

Possible Causes:

  • Defective ECU
  • Damaged controller(s) due to abnormal system voltages

Diagnostic Steps:

  • Diagnose and address all other codes first before replacing ECU
  • Check whether system voltage is within manufacturer’s recommendation
  • Inspect wiring to ECU and ensure that there are no open, shorted or broken wires
  • Reset all codes and do test drive. If the code returns you may have to replace ECU

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