Circuit/System Testing

Engine idling, observe the ignition voltage parameter with a scan tool. The ignition voltage should be between 12-15 volts.
- If the voltage is above the specified range, refer to Charging System Test for further diagnosis.
Measure the voltage on the battery with a DMM. Verify the battery voltage is between 12-15 volts.
- If the voltage is below the specified range, refer to Charging System Test for further diagnosis.
Verify that the difference between the battery voltage and the ignition voltage parameter is less than 1 volt.
- If the voltage difference is above the specified value, test for an open/high resistance on the ignition voltage circuit of the ECM.
If all circuits/connections test OK, replace the ECM.