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 message to the engine control module (ECM) that crank has been requested. The ECM then verifies that the transmission is in Park or Neutral. If it is, the ECM then supplies 12 volts to the control circuit of the STRTR relay. When this occurs, battery voltage is supplied through the switch of the STRTR relay to terminal A X1 of the starter solenoid, and the engine cranks.

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

Scan Tool Reference

Control Module References for scan tool information

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

1. Measure and record the battery voltage at the battery terminals. The voltage should be between 12.6 and 15.0 volts.

⇒	If not within the specified range, refer to Charging System Test .

2. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5 ohms between the starter motor case and the negative terminal of the battery.

⇒	If greater than the specified range, test the battery negative cable for an open/high resistance.

3. Verify that a test lamp illuminates between the starter solenoid B+ circuit ring terminal B X2 and ground.

⇒	If the test lamp does not illuminate, test the battery positive cable for an open/high resistance.

4. Remove the drive belt. Refer to the appropriate procedure listed below.

•	Drive Belt Replacement for the 2.4L (LL8) engine

•	Drive Belt Replacement - Accessory for the 5.3L (LH6) or 6.0L (LS2) engine

5. Rotate each pulley by hand. Verify that none of the engine accessories or idler pulleys are seized.

⇒	If any components are seized, replace the appropriate component.

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

⇒	If the engine is seized, refer to the appropriate procedure listed below.

•	Engine Will Not Crank - Crankshaft Will Not Rotate for the 4.2L (LL8) engine

•	Engine Will Not Crank - Crankshaft Will Not Rotate for the 5.3L (LH6) or 6.0L (LS2) engine

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.