Schematic Reference: Starting and Charging Schematics

Did you perform the Engine Electrical Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Engine Electrical

Turn the ignition switch to the START position.

Does the engine crank?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

Turn the ignition switch to the START position.

Does the starter motor relay click?

Go to Step 7

Go to Step 4

1. Remove the starter motor relay.
2. Connect a test light from the supply voltage circuit of the starter motor relay coil circuit to ground.
3. With the transmission in park, neutral or the clutch pedal depressed, turn the ignition switch to the START position.

Does the test light illuminate?

Go to Step 5

Go to Step 6

1. Connect a test light from the supply voltage circuit of the starter motor relay coil circuit to the control circuit of the starter motor relay coil circuit.
2. With the transmission in park, neutral or the clutch pedal depressed, turn the ignition switch to the START position.

Does the test light illuminate?

Go to Step 13

Go to Step 10

Is the starter equipped with over crank protection (OCP) thermal switch?

Go to Step 7

Go to Step 8

1. Turn OFF the ignition.
2. Disconnect the starter terminal switch.
3. Turn ON the ignition, with the Engine OFF.
4. Connect a 10 amp fused jumper between the starter motor relay coil control circuits of the starter terminal switch.
5. With the transmission in park, neutral or the clutch pedal depressed, turn the ignition switch to the START position.

Does the test lamp illuminate?

Go to Step 18

Go to Step 8

1. Turn OFF the ignition.
2. Disconnect the Park Neutral Position (PNP) switch refer to Park/Neutral Position and Backup Lamp Switch Replacement , Neutral Switch for the Automatic Transmission - Allison or the Clutch/Starter Interlock Switch , refer to Clutch Engine Brake Switch Replacement in Manual Transmission.
3. Turn ON the ignition, with the Engine OFF.
4. Connect a 10 amp fused jumper between the starter motor relay coil control circuits of the PNP switch, Neutral Switch or Clutch/Starter Interlock Switch.
5. With the transmission in park, neutral or the clutch pedal depressed, turn the ignition switch to the START position.

Does the test lamp illuminate?

Go to Step 16

Go to Step 13

1. Turn OFF the ignition.
2. Disconnect the starter motor relay.
3. Connect a test lamp between the battery positive voltage circuit of the Starter Motor relay switch circuit and a good ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 19

Connect a 30-amp fused jumper between the battery positive voltage circuit of the starter motor relay switch circuit and the supply voltage circuit of the starter solenoid.

Does the engine crank?

Go to Step 15

Go to Step 11

Does the fuse in the jumper open?

Go to Step 20

Go to Step 14

Test the control circuit of the starter motor relay for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 25

Go to Step 21

Test the supply voltage circuit of the starter motor relay coil circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 25

Go to Step 17

Test the supply voltage circuit of the starter solenoid for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 25

Go to Step 18

Inspect for poor connections at the starter motor relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 25

Go to Step 21

Did you find and correct the condition?

Go to Step 25

Go to Step 22

Inspect for poor connections at the ignition switch harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 25

Go to Step 23

Inspect for poor connections at the starter thermal switch/solenoid. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 25

Go to Step 24

Repair the open or high resistance in the battery positive voltage circuit of the Starter Motor relay switch circuit. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 25

--

Repair the short to ground in the supply voltage circuit of the starter solenoid. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 25

--

Replace the starter motor relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 25

--

Replace the following switches:

Did you complete the replacement?

Go to Step 25

--

Replace the ignition switch. Refer to Ignition and Start Switch Replacement .

Did you complete the replacement?

Go to Step 25

--

Replace the starter. Refer to Starter Motor Replacement .

Did you complete the replacement?

Go to Step 25

--

Operate the system for which the symptom occurred.

Did you correct the condition?

System OK

Go to Step 2

Schematic Reference: Starting and Charging Schematics

Did you preform the Engine Electrical Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Engine Electrical

Turn the ignition switch to the START position.

Does the engine crank?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

Turn the ignition switch to the START position.

Does the starter motor relay click?

Go to Step 11

Go to Step 4

Is the vehicle equipped with a manual transmission?

Go to Step 5

Go to Step 7

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, observe the Clutch Start Switch Signal parameter in the PCM data list while depressing the clutch pedal.

Does the scan tool display Released/Applied?

Go to Step 7

Go to Step 6

1. Turn OFF the ignition.
2. Disconnect the PCM harness connector.
3. Connect a test lamp between the Clutch Start Switch Signal of the PCM harness and a good ground.
4. Turn the ignition to the START position while depressing the clutch pedal.

Does the test lamp illuminate?

Go to Step 7

Go to Step 8

1. Turn OFF the ignition.
2. Disconnect the PCM harness connector.
3. Connect a test lamp between the crank voltage circuit (starter enable relay control) of the PCM harness and a good ground.
4. Turn the ignition to the START position.

Does the test lamp illuminate?

Go to Step 19

Go to Step 8

1. Remove the starter motor relay.
2. Connect a test light from the supply voltage circuit of the starter motor relay coil circuit to ground.
3. With the transmission in park, or clutch pedal depressed, turn the ignition switch to the START position.

Does the test light illuminate?

Go to Step 9

Go to Step 10

1. Connect a test light from the supply voltage circuit of the starter motor relay coil circuit to the control circuit of the starter motor relay coil circuit.
2. With the transmission in park, or clutch pedal depressed, turn the ignition switch to the START position.

Does the test light illuminate?

Go to Step 17

Go to Step 14

1. Turn OFF the ignition.
2. Disconnect the park neutral position (PNP) switch Park/Neutral Position and Backup Lamp Switch Replacement for the Automatic Transmission - Allison or Clutch Engine Brake Switch Replacement for the Manual Transmission.
3. Turn ON the ignition, with the engine OFF.
4. Connect a 10 amp fused jumper between the starter motor relay coil control circuits of the PNP switch or clutch pedal position switch.
5. With the transmission in park, or clutch pedal depressed, turn the ignition switch to the START position.

Does the test lamp illuminate?

Go to Step 18

Go to Step 15

1. Turn OFF the ignition.
2. Disconnect the starter motor relay.
3. Connect a test lamp between the battery positive voltage circuit of the starter motor relay switch circuit and a good ground.

Does the test lamp illuminate?

Go to Step 12

Go to Step 23

Connect a 30 amp fused jumper between the battery positive voltage circuit of the starter motor relay switch circuit and the supply voltage circuit of the starter solenoid.

Does the engine crank?

Go to Step 17

Go to Step 13

Does the fuse in the jumper open?

Go to Step 24

Go to Step 16

Test the control circuit of the starter motor relay for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 25

Test the supply voltage circuit of the starter motor relay coil circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 21

Test the supply voltage circuit of the starter solenoid for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 22

Inspect for poor connections at the starter motor relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 25

Did you find and correct the condition?

Go to Step 29

Go to Step 26

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 20

Important: The replacement PCM must be programmed.

Replace the PCM/ECM. Refer to Powertrain Control Module Replacement for the 8.1L engine or Engine Control Module Replacement for the 6.6L engine.

Is action complete?

Go to Step 29

--

Inspect for poor connections at the ignition switch harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 27

Inspect for poor connections at the starter solenoid. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 29

Go to Step 28

Repair the open or high resistance in the battery positive voltage circuit of the Starter Motor relay switch circuit. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 29

--

Repair the short to ground in the supply voltage circuit of the starter solenoid. Refer to Wiring Repairs .

Did you complete the repair?

Go to Step 29

--

Replace the Starter Relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 29

--

1. Replace the PNP switch. Refer to Park/Neutral Position and Backup Lamp Switch Adjustment for the Automatic Transmission - Allison.
2. Replace the Clutch Pedal Position switch. Refer to Clutch Engine Brake Switch Replacement .

Did you complete the replacement?

Go to Step 29

--

Replace the Ignition Switch. Refer to Ignition and Start Switch Replacement .

Did you complete the replacement?

Go to Step 29

--

Replace the starter. Refer to Starter Motor Replacement .

Did you complete the replacement?

Go to Step 29

--

Operate the system for which the symptom occurred.

Did you correct the condition?

System OK

Go to Step 2