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)/powertrain control module (PCM) that crank has been requested. The ECM/PCM then verifies that the transmission is in Park or Neutral. If it is, the ECM/PCM then supplies a ground to the control circuit of the STARTER/CRANK relay. When this occurs, battery voltage is supplied through the switch of the STARTER/CRANK relay to S terminal of the starter solenoid.

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

1. Verify that battery is sufficiently charged and that the battery cables are clean and tight.

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

⇒	If battery cables are not within specified range, refer to Fastener Tightening Specifications .

2. Turn the ignition switch to the start position. The starter solenoid should click.

⇒	If starter solenoid does not click, refer to Starter Solenoid Does Not Click .

3. Remove the drive belt. Refer to Drive Belt Replacement or Drive Belt Replacement - Accessory .
4. Turn the ignition switch to the START position.

⇒	If the engine cranks, inspect the engine and belt drive system for mechanical binding, seized engine, or seized generator, etc.

⇒	If the engine does not crank, refer to Engine Will Not Crank - Crankshaft Will Not Rotate for the 3.8L engine, or Engine Will Not Crank - Crankshaft Will Not Rotate for the 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L engine.

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

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

6. Using a DMM, measure the negative battery cable to the starter motor case as the ignition switch is turned to the START position. Voltage should be less than 0.5 volts.

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

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.