Circuit/System Testing
IMS Switch Circuit Malfunction
- Ignition OFF, disconnect the harness connector at the AT Inline 20-Way Connector.
- Ignition ON, verify the scan tool PNP Switch parameter displays In Gear.
- If not the specified value, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the ECM.
- Install a 3A fused jumper wire between the ignition circuit terminal 2 and ground. Verify the scan tool PNP Switch parameter reads Park/Neutral.
- If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, test or replace the IMS switch.
Crank Relay Circuit Malfunction
- Ignition OFF, disconnect the crank relay.
- Ignition OFF, test for less than 5.0 ohms between the relay ground circuit terminal 85 and ground.
- If greater than the specified range, test the relay ground circuit for an open/high resistance.
- Ignition ON, verify a test lamp illuminates between the relay switch B+ circuit terminal 30 and ground.
- If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
- Ensure the parking brake is applied and the transmission is in NEUTRAL on manual transmissions or PARK on automatic transmissions.
- Momentarily install a 40A fused jumper wire between the B+ circuit terminal 30 and the control output circuit terminal 87. The starter solenoid should engage and the engine should begin cranking.
- If the solenoid does not engage, test the control output circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the starter motor.
- Connect a test lamp between the coil control circuit terminal 86 and the coil ground circuit terminal 85.
- With the transmission range selector in park or neutral on automatic transmissions or the clutch pedal fully depressed on manual transmissions cycle the ignition between the OFF and CRANK position.
- The test lamp should turn ON and OFF when changing between the commanded states.
- If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
- If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
- If all circuits test normal, test or replace the crank relay.