Hummer H3. Manual - part 41

Diagnostic Fault Information

Circuit/System Description

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, then the ECM then supplies
12 volts to the control circuit of the PCM CNTRL relay. When this occurs, battery voltage is
supplied through the switch of the PCM CNTRL relay to the terminal A X1 of the starter
solenoid.

Reference Information

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

Circuit Testing

Circuit

Short to

Ground

Open/High

Resistance

Short to

Voltage

Signal

Performance

B+

PCM-1 Ignition Voltage

Park Neutral Signal

Relay Control

Starter Control

Ground

1. No crank
2. Cranks in any gear
3. Cranks all the time

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, verify that the scan tool ECM Ignition 1 Signal parameter displays B+.

If less than the specified value, test the PCM-1 fuse, the RUN/CRNK relay, and the
ignition voltage circuit for an open/high resistance. If the circuit tests normal, replace
the ECM.

2. Verify that no starter relay, theft deterrent, or automatic transmission DTCs are set that

would cause the ECM to disable starting.

If DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

3. Observe the scan tool ECM Crank Request Signal parameter. Place ignition switch in the

crank position. Verify that the scan tool displays Yes.

If not the specified value, refer to Power Mode Mismatch .

4. Transmission range selector in park. Verify that the scan tool ECM PNP Switch parameter

displays Park/Neutral.

If the ECM PNP Switch parameter does not indicate Park/Neutral, refer to
Circuit/System Testing.

5. Transmission range selector in park or neutral. Attempt to start the vehicle. The PCM

CNTRL relay should click and the engine should begin cranking.

If the PCM CNTRL relay does not click or the engine does not crank, refer to PCM
CNTRL.

6. If all circuits test normal, replace the ECM.

Circuit/System Testing

PNP Switch Circuit Malfunction

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

1. Inspect the range selector lever cable for proper adjustment. Refer to Range Selector

Lever Cable Adjustment (3.7L) or Range Selector Lever Cable Adjustment (5.3L) .

2. Inspect the park/neutral position switch for proper adjustment. Refer to Park/Neutral

Position and Backup Lamp Switch Adjustment .

3. Ignition OFF, disconnect the harness connector from the park/neutral switch.

4. With the PNP switch in the following positions, test for infinite resistance between the

ground terminal 7 and the signal terminal 3.

If not the specified value, replace the PNP switch.

5. With the PNP switch in the following positions, test for less than 2.0 ohms between the

ground terminal 7 and the signal terminal 3.

If greater than the specified range, replace the PNP switch.

PCM CNTRL Relay Circuit Malfunction

1. Ignition OFF, disconnect the PCM CNTRL relay.

2. With the ignition OFF and the scan tool disconnected, open and close the drivers door, and

wait 30 seconds. Test for less than 1.5 ohms between the ground circuit terminal 85 and
ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 30 and ground.

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

4. Ensure the parking brake is applied and the transmission is in PARK. Momentarily install a

40A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal
87. The starter solenoid should engage and the engine should begin cranking.

If the solenoid does not engage, test the starter control circuit for a short to ground or
an open/high resistance. If the circuit tests normal, test or replace the starter motor.

5. Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

85.

6. With the transmission range selector in park or neutral, cycle the ignition between the OFF

and CRANK position. The test lamp should turn ON and OFF when changing between the
commanded states.

If the test lamp is always ON, test the control circuit for a short to voltage. If the
circuit tests normal, replace the ECM.

If the test lamp is always OFF, test the control circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the ECM.

7. If all circuits test normal, test or replace the PCM CNTRL relay.

Component Testing

PNP Switch

1. Inspect the range selector lever cable for proper adjustment. Refer to Range Selector

Lever Cable Adjustment (3.7L) or Range Selector Lever Cable Adjustment (5.3L) .

2. Inspect the park/neutral position switch for proper adjustment. Refer to Park/Neutral

Position and Backup Lamp Switch Adjustment .

3. Ignition OFF, disconnect the harness connector from the park/neutral switch. Refer to

Park/Neutral Position and Backup Lamp Switch Replacement (3.7L) or
Park/Neutral Position and Backup Lamp Switch Replacement (5.3L) .

4. With the PNP switch in the following positions, test for infinite resistance between the

ground terminal 7 and the signal terminal 3.

If not the specified value, replace the PNP switch.

5. With the PNP switch in the following positions, test for less than 2.0 ohms between the

ground terminal 7 and the signal terminal 3.

If greater than the specified range, replace the PNP switch.

Relays

2008 Hummer H3

2008 ENGINE Engine Electrical - H3

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