Page 1417 of 4284

TEST ACTION APPLICABILITY
4 Turn the ignition off.
Install a substitute relay in place of the Lift Pump Relay.
Turn the ignition on.
With the DRB, actuate the Lift Pump Relay.
Does the Lift Pump Motor cycle on and off?All
Ye s®Replace the Lift Pump Relay.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 5
5 Turn the ignition off.
Disconnect the Lift Pump Motor harness connector.
Remove the Lift Pump Relay.
Turn the ignition on.
Measure the voltage on the Lift Pump Relay Output circuit.
Is the voltage above 1.0 volt?All
Ye s®Repair the Lift Pump Relay Output circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 6
6 Turn the ignition off.
Disconnect the Lift Pump Motor harness connector.
Remove the Lift Pump Relay.
Measure the resistance between ground and the Lift Pump Relay Output circuit.
Is the resistance above 100k ohms?All
Ye s®Go To 7
No®Repair the Lift Pump Relay Output circuit for a short to ground.
Inspect the fuse and replace as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
7 Turn the ignition off.
Disconnect the Lift Pump Motor harness connector.
Remove the Lift Pump Relay.
Connect a jumper wire across Lift Pump Relay connector cavities 30 and 87.
Using a 12-volt test light connected to ground, check the Lift Pump Relay Output
circuit.
Is the test light illuminated brightly?All
Ye s®Go To 8
No®Repair the Lift Pump Relay Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
8 Turn the ignition off.
Disconnect the Lift Pump Motor harness connector.
Using a 12-volt test light connected to 12-volts, check the Lift Pump Ground circuit.
Is the test light illuminated brightly?All
Ye s®Go To 9
No®Repair the Lift Pump Ground circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
198
DRIVEABILITY - DIESEL
*CHECKING THE LIFT PUMP MOTOR OPERATION ÐContinued
Page 1418 of 4284
TEST ACTION APPLICABILITY
9 If there are no possible causes remaining, view repair. All
Repair
Replace the Lift Pump Motor in accordance with the Service
Information.
Perform ROAD TEST VERIFICATION - VER-2.
199
DRIVEABILITY - DIESEL
*CHECKING THE LIFT PUMP MOTOR OPERATION ÐContinued
Page 1419 of 4284

Symptom:
*CHECKING THE MAF SENSOR CALIBRATION
POSSIBLE CAUSES
CHECKING THE MAF SIGNAL AT 2000 RPM
CHECKING THE MAF SIGNAL AT 3000 RPM
CHECKING THE MAF SIGNAL AT 4000 RPM
CHECKING THE MAF SIGNAL AT IDLE
TEST ACTION APPLICABILITY
1 Allow the engine to idle for 2 minutes.
NOTE: The induction tubes connected to the MAF Sensor and the turbo-
charger must be properly connected and without damage or restrictions.
With the DRBIIItin Sensors, read the MASS AIR FLOW Volts.
Is the voltage between 2.0 and 2.7 volts?All
Ye s®Go To 2
No®Replace the Mass Air Flow Sensor.
2 Allow the engine to idle for 2 minutes.
NOTE: The induction tubes connected to the MAF Sensor and the turbo-
charger must be properly connected and without damage or restrictions.
With the DRBIIItin Sensors, read the MASS AIR FLOW Volts.
With the transmission in Neutral and the parking brake set, increase engine speed
to 2000 rpm and note the DRB reading.
Is the voltage between 2.8 and 3.5 volts?All
Ye s®Go To 3
No®Replace the Mass Air Flow Sensor.
3 Allow the engine to idle for 2 minutes.
NOTE: The induction tubes connected to the MAF Sensor and the turbo-
charger must be properly connected and without damage or restrictions.
With the DRBIIItin Sensors, read the MASS AIR FLOW Volts.
With the transmission in Neutral and the parking brake set, increase engine speed
to 3000 rpm and note the DRB reading.
Is the voltage between 3.5 and 4.1 volts?All
Ye s®Go To 4
No®Replace the Mass Air Flow Sensor.
4 Allow the engine to idle for 2 minutes.
NOTE: The induction tubes connected to the MAF Sensor and the turbo-
charger must be properly connected and without damage or restrictions.
With the DRBIIItin Sensors, read the MASS AIR FLOW Volts.
With the transmission in Neutral and the parking brake set, increase engine speed
to 4000 rpm for 5.0 seconds and note DRB reading.
Is the voltage between 3.8 and 4.5 volts?All
Ye s®Test Complete.
No®Replace the Mass Air Flow Sensor.
200
DRIVEABILITY - DIESEL
Page 1420 of 4284

Symptom:
*CHECKING THE SPEED CONTROL OPERATION
POSSIBLE CAUSES
CHECKING CRUISE SWITCHES
CHECKING THE BRAKE SWITCH INPUT
CHECKING THE ECM FOR DTC'S
CHECKING THE VSS SIGNAL
CLUTCH PEDAL SWITCH
CLUTCH PEDAL SWITCH SENSE CIRCUIT OPEN
CLUTCH PEDAL SWITCH SENSE CIRCUIT SHORTED TO GROUND
ECM
ECM
INTERMITTENT CONDITION
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read the ECM DTCs.
Are there any ECM DTC's present?All
Ye s®Refer to symptom list for problems related to the ECM DTC.
Perform SPEED CONTROL VERIFICATION - VER-4.
No®Go To 2
2 Test drive the vehicle above 60 Km/h (35 mph).
Attempt to Set the Speed Control.
Is the Speed Control function operating properly?All
Ye s®Test Complete.
No®Go To 3
3 Start the engine.
With the DRB, read the CRUISE SW VOLTS.
Observe the cruise switch volts on the DRB while pressing and holding each cruise
button separately.
NOTE: Pressing each cruise button should result in the following voltages:
ON/OFF 0.0 - 0.3v, SET 3.58 - 3.99v, RESUME/ACCEL 4.19 - 4.59v, CANCEL 1.28
- 1.68v, COAST 2.69 - 3.01v, No Button Pressed 4.8 - 5.2v
Does each switch provide the correct voltage?All
Ye s®Go To 4
No®Refer to symptom list for problems related to S/C Switches.
Perform SPEED CONTROL VERIFICATION - VER-4.
201
DRIVEABILITY - DIESEL
Page 1421 of 4284

TEST ACTION APPLICABILITY
4 Turn the ignition on.
With the DRBIIItin Sensors, read the Vehicle Speed Sensor signal.
Have an assistant drive the vehicle while you are observing the Vehicle Speed Signal
on the DRB.
While observing vehicle speed signal note any rapid changes (signal drop-outs) in the
reading that do not correspond with actual vehicle speed.
Is the DRB displaying an accurate Vehicle Speed Signal?All
Ye s®Go To 5
No®Refer to symptom list for problems related to the Vehicle Speed
Sensor.
Perform SPEED CONTROL VERIFICATION - VER-4.
5 Turn the ignition on.
With the DRBIIItin Inputs/Outputs, read the Primary and Secondary switch states
while pressing and releasing the Brake Pedal several times.
Did the DRB indicate the correct brake pedal state when pressing and releasing the
Brake Pedal?All
Ye s®Go To 6
No®Refer to symptom list for problems related to Brake Switch input.
Perform SPEED CONTROL VERIFICATION - VER-4.
6 Turn the ignition on.
With the DRBIIItin Inputs/Outputs, read the Clutch switch states while pressing
and releasing the Clutch Pedal several times.
Did the DRB indicate the correct clutch pedal state when pressing and releasing the
Clutch Pedal?All
Ye s®Go To 7
No®Go To 8
7WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary.
Perform SPEED CONTROL VERIFICATION - VER-4.
No®Replace and program the ECM in accordance with the Service
Information.
Perform SPEED CONTROL VERIFICATION - VER-4.
202
DRIVEABILITY - DIESEL
*CHECKING THE SPEED CONTROL OPERATION ÐContinued
Page 1422 of 4284

TEST ACTION APPLICABILITY
8 Turn the ignition off.
Disconnect the Clutch Pedal Switch harness connector.
Turn the ignition on.
With the DRBIIItin Inputs/Outputs, read the Clutch Switch state while using a
jumper wire to connect the Clutch Pedal Switch Sense circuit to ground at the Clutch
Pedal Switch harness connector.
NOTE: Leave jumper connected to ground for 5 seconds then disconnect
jumper and note DRB reading for both conditions.
Does the DRB display RELEASED and PRESSED?All
Ye s®Replace the Clutch Pedal Switch.
Perform SPEED CONTROL VERIFICATION - VER-4.
No®Go To 9
9 Turn the ignition off.
Disconnect the Clutch Pedal Switch harness connector.
Measure the resistance of the Clutch Pedal Switch Sense circuit.
Is the resistance below 10.0 ohms?All
Ye s®Go To 10
No®Repair the Clutch Pedal Switch Sense circuit for an open.
Perform SPEED CONTROL VERIFICATION - VER-4.
10 Turn the ignition off.
Disconnect the Clutch Pedal Switch harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the Clutch Pedal Switch Sense circuit.
Is the resistance below 1000 ohms?All
Ye s®Repair the Clutch Pedal Switch Sense circuit for a short to
ground.
Perform SPEED CONTROL VERIFICATION - VER-4.
No®Replace and program the ECM in accordance with the Service
Information.
Perform SPEED CONTROL VERIFICATION - VER-4.
203
DRIVEABILITY - DIESEL
*CHECKING THE SPEED CONTROL OPERATION ÐContinued
Page 1423 of 4284

Symptom:
*CHECKING THE VEHICLE SPEED SIGNAL
POSSIBLE CAUSES
VEHICLE SPEED SENSOR SIGNAL CIRCUIT SHORTED TO SENSOR GROUND
CHECK FOR VSS DTC
IGNITION SWITCH OUTPUT CIRCUIT OPEN
SPEEDOMETER PINION AND DRIVE TEETH DAMAGED
VEHICLE SPEED SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
VEHICLE SPEED SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
ENGINE CONTROL MODULE - SHORTED TO VOLTAGE
VEHICLE SPEED SENSOR SIGNAL CIRCUIT OPEN
SENSOR GROUND CIRCUIT OPEN
VEHICLE SPEED SENSOR
ENGINE CONTROL MODULE - INTERNAL FAULT
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRB, select Engine, then Sensors.
While an assistant is test driving the vehicle, note the Vehicle Speed reading on the
DRB.
While reading the VSS Signal, note any rapid changes (signal drop-outs) that do not
correspond with actual vehicle speed.
Does the DRB display an accurate vehicle speed reading?All
Ye s®Test Complete.
No®Go To 2
2 Turn the ignition on.
With the DRB, read ECM DTCs.
Are any VSS DTCs present?All
Ye s®Refer to symptom list for problems related to VSS DTCs.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 3
3 Turn the ignition off.
Remove the Vehicle Speed Sensor.
Inspect the Speedometer Pinion and drive teeth on the Output Shaft (located in the
transmission).
Inspect the VSS for metal debris and damage to the Sensor and connector.
Are both components OK?All
Ye s®Go To 4
No®Repair or replace the Speedometer Pinion or internal components
as necessary in accordance with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
204
DRIVEABILITY - DIESEL
Page 1424 of 4284

TEST ACTION APPLICABILITY
4 Turn the ignition off.
Disconnect the Vehicle Speed Sensor harness connector.
Turn the ignition on.
Measure the voltage of the Ignition Switch Output circuit in the Vehicle Speed Sensor
harness connector.
Is the voltage above 10.0 volts?All
Ye s®Go To 5
No®Repair the Ignition Switch Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
5 Turn the ignition off.
Disconnect the Vehicle Speed Sensor harness connector.
Turn the ignition on.
Measure the voltage of the Vehicle Speed Sensor Signal circuit.
Is the voltage above 5.5 volts?All
Ye s®Go To 6
No®Go To 8
6 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the Vehicle Speed Sensor harness connector.
Remove the ECM/PCM Relay from the PDC.
Connect a jumper wire between cavity 30 and cavity 87 of the ECM/PCM Relay
connector.
Turn the ignition on.
Measure the voltage of the Vehicle Speed Sensor Signal circuit.
Is the voltage below 1.0 volt?All
Ye s®Go To 7
No®Repair the Vehicle Speed Sensor Signal circuit for a short to
voltage.
Perform ROAD TEST VERIFICATION - VER-2.
7 If there are no possible causes remaining, view repair. All
Repair
Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
8 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the Vehicle Speed Sensor harness connector.
Measure the resistance between ground and the Vehicle Speed Sensor Signal circuit.
Is the resistance above 100k ohms?All
Ye s®Go To 9
No®Repair the Vehicle Speed Sensor Signal circuit for a short to
ground.
Perform ROAD TEST VERIFICATION - VER-2.
205
DRIVEABILITY - DIESEL
*CHECKING THE VEHICLE SPEED SIGNAL ÐContinued