
3.EXCESSIVE RESISTANCE IN THE CASE GROUND
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands
near the pulleys, belts, or fan. Do notwear loose clothing. Failure to follow these instructions can result in
personal injury or death.
Start the engine.
Warm the engine to operating temperature.
NOTE: Make sure all wires are clear of the engine’s moving parts.
Measure the voltage between the Generator Case and Battery ground post.
Is the voltage above 0.1 of a volt?
Ye s>>
Repair the excessive resistance in the Generator Case Ground.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 4
4.GENERATOR OPERATION
Turn the ignition off.
Disconnect the Generator Field harness connector.
Using a 12-volt test light, jump across the Generator Field harness con-
nector.
Ignition on, engine not running.
With a scan tool, actuate theGenerator Field Driver.
Does the test light illuminate brightly and flash on and off?
Ye s>>
Replace the Generator.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 5
5.(K20) GEN FIELD CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE
Turn the ignition off.
Disconnect the C2 PCM harness connector.
Ignition on, engine not running.
Measure the voltage on the (K20) Gen Field Control circuit in the Gen-
erator Field harness connector.
Is the voltage above 1.0 volt?
Ye s>>
Repair the short to battery voltage in the (K20) Gen Field
Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 6

Possible Causes
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
(A109) FUEL PUMP RELAY OUTPUT CIRCUIT OPEN
FUEL PUMP RELAY
FUEL PUMP
Diagnostic Test
1.FUEL PUMP OPERATION
Ignition on, engine not running.
With a scan tool, actuate the Fuel System test.
NOTE: It may be necessary to use a mechanics stethoscope in the next step.
Listen for fuel pump operation at the fuel tank.
Does the Fuel Pump operate?
Ye s>>
Go To 2
No>>
Go To 5
CAUTION: Stop All Actuations.
2.FUEL PRESSURE
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Install a fuel pressure gauge at the engine.
Ignition on, engine not running.
With the scan tool, actuate the ASD FuelSystem test and observe the fuel pressure gauge.
NOTE: NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Choose a conclusion that best matches your fuel pressure reading.
Below Specification
Go To 3
Within Specification
Te s t C o m p l e t e .
Above Specification
Replace the fuel filter/fuel pressure regulator.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
CAUTION: Stop All Actuations.
3.RESTRICTED FUEL SUPPLY LINE
Turn the ignition off.
WARNING: The fuel system is under a constant pressure even with the engine off. Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released.
Raise vehicle on hoist, and disconnect the fuel pressure line at the fuel pump module.
Install special tool #6539 (5/16
) or #6631(3/8) fuel line adapter and the fuel pressure gauge between the fuel sup-
ply line and the fuel pump module.
Ignition on, engine not running.
With the scan tool, actuate the ASD FuelSystem test and observe the fuel pressure gauge.

NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
CAUTION: Stop All Actuations.
Is the fuel pressure within specification now?
Ye s>>
Repair/replace fuel supply line as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 4
4.CHECKING FUEL INLET STRAINER
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.
Is the Fuel Inlet Strainer plugged?
Ye s>>
Replace the Fuel Pump Inlet Strainer.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Replace the Fuel Pump Module.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
5.(A109) FUEL PUMP RELAY OUTPUT CIRCUIT OPEN
Turn the ignition off.
Remove the Fuel Pump Relay from the IPM.
Disconnect the Fuel Pump Module harness connector.
Measure the resistance of the (A109) Fuel Pump Relay Output circuit
from the relay connector to the fuel pump module connector.
Is the resistance below 5.0 ohms?
Ye s>>
Replace the Fuel Pump Relay.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
No>>
Repair the open in the (A109) Fuel Pump Relay Output cir-
cuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)

*HARD START FUEL SYSTEM
For a complete wiring diagramRefer to Section 8W.
Possible Causes
FUEL CONTAMINATION
RESTRICTED FUEL SUPPLY LINE
FUEL PUMP INLET STRAINER PLUGGED
FUEL PUMP MODULE
FUEL INJECTOR(S)
Diagnostic Test
1.CHECKING FUEL PRESSURE
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Install a fuel pressure gauge at the engine.
Ignition on, engine not running.
With a scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.
NOTE: NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Choose a conclusion that best matches your fuel pressure reading.
Below Specification
Go To 2
Within Specification
Go To 4
2.RESTRICTED FUEL SUPPLY LINE
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Raise vehicle on hoist, and disconnect the fuel supply line at the fuel pumpmodule.
Install special tool #6539 (5/16
) #6631(3/8) fuel line adapter and the fuel pressure gauge between the fuel supply
line and the fuel pump module.
Ignition on, engine not running.
With the scan tool, actuate the ASD FuelSystem test and observe the fuel pressure gauge.
NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Is the fuel pressure within specification?
Ye s>>
Visually and physically inspect the fuel supply lines between the fuel tank and the fuel rail. Repair/re-
place as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3

3.CHECKING THE FUEL INLET STRAINER
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.
Is the Fuel Inlet Strainer plugged?
Ye s>>
Replace the Fuel Pump Inlet Strainer.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Replace the Fuel Pump Module.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
4.FUEL PUMP MODULE
NOTE: Before continuing visually and physically inspect the fuel delivery system for external leaks or dam-
age. Repair / replace as necessary.
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Install special tool #6539 (5/16
) or #6631 (3/8) fuel line adapter.
Install the fuel pressure gauge.
Start the engine and allow the fuel system to reach maximum pressure.
Turn the ignition off.
NOTE: Fuel specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Using special tool #C4390, Hose Clamp Pliers, pinch the rubber fuel line between the fuel pressure gauge and the
engine.
Monitor the fuel pressure gauge for a minimum of 5 minutes.
NOTE: The pressure should not fall below 241 KPa (35 psi)
Does the fuel pressure drop?
Ye s>>
Replace Fuel Pump Module.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 5
5.FUEL INJECTOR(S)
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Remove special tool #C4390.
Start the engine and allow the fuel system to reach maximum pressure.
Turn the ignition off.
NOTE: Fuel specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Move special tool #C4390, Hose Clamp Pliers, from between the fuel pressure gauge and the engine to between
the fuel pressure gauge and fuel pump module.
Monitor the fuel pressure gauge for a minimum of 5 minutes.

*FUEL PRESSURE LEAK DOWN
For a complete wiring diagramRefer to Section 8W.
Possible Causes
FUEL PUMP MODULE
FUEL INJECTOR(S)
Diagnostic Test
1.FUEL PUMP MODULE
NOTE: Before continuing visually and physically inspect the fuel delivery system for external leaks or dam-
age. Repair / replace as necessary.
Turn the ignition off.
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Install special tool #6539 (5/16
) or #6631 (3/8) fuel line adapter.
Install the fuel pressure gauge.
Start the engine and allow the fuel system to reach maximum pressure.
Turn the ignition off.
NOTE: Fuel specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Using special tool #C4390, Hose Clamp Pliers, pinch the rubber fuel line between the fuel pressure gauge and the
engine.
Monitor the fuel pressure gauge for a minimum of 5 minutes.
NOTE: The pressure should not fall below 241 KPa (35 psi)
Does the fuel pressure drop?
Ye s>>
Replace Fuel Pump Module.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 2
2.FUEL INJECTOR(S)
WARNING: The fuel system is under a constant pressure (even with the engineoff). Before testing or ser-
vicing any fuel system hose, fitting or line, the fuel system pressure mustbe released. Failure to follow
these instructions can result in personal injury or death.
Remove special tool #C4390.
Start the engine and allow the fuel system to reach maximum pressure.
Turn the ignition off.
NOTE: NOTE: Fuel specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).
Move special tool #C4390, Hose Clamp Pliers, from between the fuel pressure gauge and the engine to between
the fuel pressure gauge and fuel pump module.
Monitor the fuel pressure gauge for a minimum of 5 minutes.
NOTE: The pressure should not fall below 241 KPa (35 psi)
Does the fuel pressure drop?
Ye s>>
Replace the leaking fuel injectors.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Te s t C o m p l e t e .

Possible Causes
MECHANICAL CONDITION
BATTERY CIRCUIT RESISTANCE TOO HIGH
FUSED IGNITION SWITCH OUTPUT CIRCUITS
FUSED B+ CIRCUIT OPEN
(T752) STARTER RELAY CONTROL CIRCUIT OPEN
(T750) STARTER RELAY OUTPUT CIRCUIT OPEN
TRANSMISSION RANGE SENSOR
STARTER RELAY
STARTER
Diagnostic Test
1.MECHANICAL CONDITION
NOTE: Verify the battery is fully charged and capable of passing a load testbefore continuing.
WARNING: Make sure the battery is disconnected, then wait two minutes before proceeding. Failure to do
so may result in personal injury or possible death.
Turn the engine over by hand to make sure the engine is not seized.
Is the engine able to turn over?
Ye s>>
Go To 2
No>>
Repair the mechanical condition preventing the starter motor from cranking.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.TRANSMISSION RANGE SENSOR
Turn the ignition off.
Disconnect the TRS harness connectors.
Move the Gear selector through all gear positions, from Park to 1st and
back.
While moving the gear selector through each gear, measure the resis-
tance between ground and the TRS (T41) Sense (P/N Position Switch
Sense) circuit at the TRS connector.
NOTE: The circuit is grounded in Park and Neutral and open in the
other positions.
Did the resistance change from above 100 kohms (open) to
below 10.0 ohms (grounded) ?
Ye s>>
Go To 3
No>>
Replace the Transmission Range Sensor.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)

3.EXCESSIVE RESISTANCE IN THE BATTERY CIRCUIT
Turn the ignition off.
Check the Battery Cables for excessive resistance using the service information procedure.
Did either Battery Cable have a voltage drop greater than 0.2 of a volt?
Ye s>>
Repair the excessive resistance in the Battery circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 4
4.STARTER RELAY
Turn ignition off.
Remove the Starter Relay from IPM.
CAUTION: The Parking Brake must be on and the Transmission must be in park for a vehicle equipped with
an automatic transmission.
WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands
near the pulleys, belts, or fan. Do notwear loose clothing. Failure to follow these instructions can result in
personal injury or death.
Briefly connect a jumper wire from the Internal Fused B+ circuit to the (T750) Starter Relay Output circuit.
Did the Starter Motor crank the engine?
Ye s>>
Go To 5
No>>
Go To 7
5.(T751) FUSED IGNITION SWITCH OUTPUT CIRCUIT
Ignition on, engine not running.
Using a 12-volt test light, probe the (T751) Fused Ignition Switch Output circuit in the Starter Relay connector.
While observing 12-volt test light, hold ignition key in the start position.
Does the test light illuminate brightly?
Ye s>>
Go To 6
No>>
Repair the excessive resistance in the(T751)FusedIgnitionSwitchOutput circuit. Inspect related fuses
and repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)