When the ignition switch is placed in the START position, a discrete signal is supplied to the body control module (BCM) notifying it that the ignition is in the START position. The BCM then sends a serial data message to the engine control module (ECM) that crank has been requested. The ECM monitors the park/neutral position switch. If the transmission is in Park or Neutral, and there are no DTCs that inhibit engine starting, then the ECM supplies voltage to the control circuit of the START relay. When this occurs, battery voltage is supplied through the START relay to S terminal of the starter solenoid. The starter solenoid energizes, and supplies battery voltage to the starter from the B terminal to crank the engine.

Schematic Reference

Starting and Charging Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Starting System Description and Operation

Electrical Information Reference

Attempt to start the engine. Verify that the starter solenoid clicks.

1. Verify that the battery is sufficiently charged and that the battery cables are clean and tight. Refer to Charging System Test.

⇒	If the battery is not sufficiently charged, refer to Battery Charging .

⇒	If the battery cables are not clean and tight, refer to Fastener Tightening Specifications .

2. Using a DMM, measure voltage between the positive battery terminal and terminal B at the solenoid as the ignition switch is turned to the START position. Voltage should be less than 0.5 volt.

⇒	If greater than the specified value, replace the positive battery cable.

3. Using a DMM, measure voltage between the negative battery terminal and the starter motor case as the ignition switch is turned to the START position. Voltage should be less than 0.5 volt.

⇒	If greater than the specified value, replace the negative battery cable.

4. Remove the drive belt. Refer to Drive Belt Replacement for the 2.2L (L61) engine, or Drive Belt Replacement for the 3.5L (LZ4) engine.
5. Attempt to start the engine, with the drive belt removed.

⇒	If the engine cranks, inspect the engine accessories and belt drive system for mechanical binding.

6. Attempt to rotate the crankshaft using a breaker bar, or other suitable tool. Verify that the engine is not seized.

⇒	If the engine is seized, refer to Engine Will Not Crank - Crankshaft Will Not Rotate for the 2.2L (L61) engine, or Engine Will Not Crank - Crankshaft Will Not Rotate for the 3.5L (LZ4) engine.

7. If all circuits test normal, replace the starter motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.