The engine control module (ECM) controls engine cranking based on a power mode input and the status of the clutch start switch (manual transmission) or the internal mode switch (IMS) (automatic transmission).

On manual transmission vehicles, with the clutch depressed, voltage at the ECM PNP/Clutch Start Switch Signal circuit is high. On automatic transmission vehicles, with the vehicle in Park or Neutral, the Park/Neutral Signal circuit is low. These inputs indicates to the ECM that conditions are acceptable for cranking. When a power mode crank request is seen, the ECM grounds the starter relay coil control circuit. This energizes the coil side of the relay, which pulls the switch side of the relay closed, applying voltage to the starter S-terminal and engaging the starter solenoid.

A misadjusted IMS switch or clutch start switch may result in a starter solenoid does not click condition. The adjustment process can be found in the replacement procedure for the component.

Schematic Reference

Starting and Charging Schematics

Connector End View Reference

Engine Electrical Connector End Views

Description and Operation

Starting System Description and Operation

Electrical Information Reference

Scan Tool Reference

Special Tools Required

J 45681 Jumper Harness

Automatic Transmission

1. Ignition ON, transmission in Park or Neutral, verify the scan tool PNP Switch parameter reads Park/Neutral.

⇒	If not the specified value refer to IMS Switch Circuit Malfunction.

2. Command the Starter Relay ON with a scan tool. The starter solenoid should engage and the engine should crank.

⇒	If the solenoid does not engage, refer to Crank Relay Circuit Malfunction.

⇒	If the solenoid engages but the engine does not crank, refer to Starter Solenoid Clicks, Engine Does Not Crank .

Manual Transmission

1. Ignition ON, clutch pedal depressed, verify the scan tool Clutch Start Switch parameter reads Applied.

⇒	If not the specified value refer to Clutch Start Switch Circuit Malfunction.

2. Command the Starter Relay ON with a scan tool. The starter solenoid should engage and the engine should crank.

⇒	If the solenoid does not engage, refer to Crank Relay Circuit Malfunction.

⇒	If the solenoid engages but the engine does not crank, refer to Starter Solenoid Clicks, Engine Does Not Crank .

IMS Switch Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the AT Inline 20-Way Connector.
2. 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.

3. 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.

4. If all circuits test normal, test or replace the IMS switch.

Clutch Start Switch Circuit Malfunction

1. Ignition OFF, disconnect the harness connector at the clutch start switch.
2. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal A and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

3. Verify the scan tool Clutch Start Switch parameter reads Released.

⇒	If not the specified value, test the signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the ECM.

4. Install a 3A fused jumper wire between the ignition circuit terminal A and the signal circuit terminal B. Verify the scan tool Clutch Start Switch parameter reads Applied.

⇒	If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the Clutch Start Switch.

Crank Relay Circuit Malfunction

1. Ignition OFF, disconnect the CRANK relay.
2. Ignition ON, transmission in Park/Neutral (automatic transmission) or clutch pedal depressed (manual transmission), verify a test lamp illuminates between the relay coil ignition circuit terminal and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

3. Verify a test lamp illuminates between the relay switch B+ circuit terminal and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the CRANK fuse is open, test the relay controlled output circuit for a short to ground.

4. Connect a test lamp between the relay coil ignition circuit terminal and the relay coil control circuit terminal.

Important: The engine may begin to crank.

5. Ignition ON, transmission in Park/Neutral (automatic transmission) or clutch pedal depressed (manual transmission), command the Start Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the ECM.

⇒	If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or and open/high resistance. If the circuit tests normal, replace the ECM.

6. Connect the CRANK relay.
7. Install a test lamp between the starter S terminal and ground.

Important: The engine may begin to crank.

8. Ignition ON, transmission in Park/Neutral (automatic transmission) or clutch pedal depressed (manual transmission), command the Start Relay ON with a scan tool. The test lamp should illuminate.

⇒	If the test lamp does not illuminate, test the relay controlled output circuit for an open/high resistance. If the circuit tests normal, test or replace the CRANK relay.

9. If all circuits test normal, test or replace the starter.

IMS Switch

1. Ignition OFF, disconnect the harness connector at the AT Inline 20-Way Connector.
2. Connect the J44152 jumper harness to the transmission side of the 20-way connector.
3. With the IMS switch in each of the following positions, test for less than 2.0 ohms of resistance between the signal circuit terminal 2 and the ground circuit terminal 4.

•

Park

•

Neutral

⇒	If greater than the specified range, test both circuits for an open/high resistance. If a circuit fault is found, replace the internal transmission harness. If the circuit tests normal, replace the IMS switch.

4. With the IMS switch in each of the following positions, test for infinite resistance between the signal circuit terminal 2 and the ground circuit terminal 4.

•

Reverse

•

D

•

3

•

2

•

1

⇒	If less than the specified range, test both circuits for a short to ground or a short to each other. If a circuit fault is found, replace the internal transmission harness. If the circuit tests normal, replace the IMS switch.

Clutch Start Switch

1. Ignition OFF, disconnect the harness connector at the clutch start switch.
2. With the switch in the open position, test for infinite resistance between the B+ terminal A and the signal terminal B.

⇒	If not the specified value, replace the clutch start switch.

3. With the switch in the closed position, test for less than 2.0 ohms of resistance between the B+ terminal A and the signal terminal B.

⇒	If greater than the specified range, replace the clutch start switch.

CRANK Relay

1. Ignition OFF, disconnect the CRANK relay.
2. Test for 60-180 ohms of resistance between terminals 85 and 86.

⇒	If not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified value, replace the relay.

4. Install a 20-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms of resistance between terminals 30 and 87.

⇒	If greater than specified range, replace the relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.