Low Voltage or Loss of Power/Ground during ECM Diagnosis

When performing diagnosis on a vehicle for several Engine Control Module (ECM)-related DTCs, it’s critical to check for conditions that may cause low battery voltage or a momentary loss of power or ground to the ECM. Verify that there are not any power or ground concerns before replacing the K20 ECM.

A high number of ECMs with no trouble found have been replaced on vehicles equipped with the 5.3L V8 engine (RPO L83) and 1.5 4-cylinder engine (RPO LFV). (Fig. 18)

Fig. 18

The following ECM DTCs may be set:

DTC P0601     Control Module Read Only Memory Performance

DTC P0602     Control Module Not Programmed

DTC P0603     Control Module Long Term Memory Reset

DTC P0604     Control Module Random Access Memory Performance

DTC P0606     Control Module Processor Performance

DTC P062B     Control Module Fuel Injector Control Performance

DTC P062F     Control Module Long Term Memory Performance

DTC P0630     VIN Not Programmed or Mismatched – ECM

DTC P16F3     Control Module Redundant Memory Performance

DTC P262B     Control Module Power Off Timer Performance


These DTCs are related to internal microprocessor integrity conditions in the ECM as well as incomplete ECM programming.

If any of these DTCs are set, verify that the battery cables are clean and tight and that the battery is fully charged. In addition, check that all ECM power and ground supply circuits do not have an open or high resistance and that there are not any connection or terminal tension issues. Low voltage or a temporary loss of power or ground to the ECM may cause a DTC to set.

TIP: The ECM can withstand normal current draws that are associated with vehicle operations. However, avoid overloading any of these circuits when testing for opens or shorts. Do not ground or apply voltage to any of the ECM circuits unless called out in the appropriate Service Information diagnostic procedures. These circuits should only be tested with a DMM unless the diagnostic procedure instructs otherwise.


– Thanks to Tracy Lucas

Engine ID Needed during ECM Programming
Excessive High Pressure Fuel Pump Roller Pin Movement

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