
Symptom List:
P1482-GLOW PLUG MODULE - COMMUNICATION ERROR
P2537-GLOW PLUG CONTROL CIRCUIT PREGLOW FAULT
P2537-GLOW PLUG CONTROL CIRCUIT PREGLOW SHORT TO
GROUND
P2537-GLOW PLUG CONTROL CIRCUIT PREGLOW SHORT TO
VOLTAGE
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be P1482-GLOW PLUG MODULE -
COMMUNICATION ERROR.
POSSIBLE CAUSES
ENGINE CONTROL MODULE
GLOW PLUG CONTROL SIGNAL CIRCUIT OPEN
GLOW PLUG CONTROL SIGNAL CIRCUIT SHORTED TO GROUND
GLOW PLUG CONTROL SIGNAL CIRCUIT SHORTED TO VOLTAGE
GLOW PLUG MODULE
INTERMITTENT CONDITION
TEST ACTION APPLICABILITY
1NOTE: If the ECM detects and stores a DTC, the ECM also stores the
engine/vehicle operating conditions under which the DTC was set. Some of
these conditions are displayed on the DRB at the same time the DTC is
displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to
duplicate these conditions may assist when checking for an active DTC.
Turn the ignition on.
With the DRB, erase ECM DTCs.
Perform several engine run cycles, turning the ignition off for at least 20 seconds
between each engine run cycle.
Turn the ignition on.
With the DRB, read ECM DTCs.
Did this DTC set again?All
Ye s!Go To 2
No!Go To 6
2 Turn the ignition off.
Disconnect the Glow Plug Module harness connectors.
Disconnect the ECM harness connectors.
Measure the resistance of the Glow Plug Control Signal circuit.
Measure the resistance of the Glow Plug Module Control circuit.
Is the resistance below 10.0 ohms?All
Ye s!Go To 3
No!Repair the Glow Plug Control Signal circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
80
DRIVEABILITY - DIESEL

TEST ACTION APPLICABILITY
1NOTE: If the ECM detects and stores a DTC, the ECM also stores the
engine/vehicle operating conditions under which the DTC was set. Some of
these conditions are displayed on the DRB at the same time the DTC is
displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to
duplicate these conditions may assist when checking for an active DTC.
Turn the ignition on.
With the DRB, erase ECM DTCs.
Perform several ignition cycles leaving the ignition on for at least 10 seconds then off
for 10 seconds.
With the DRBIIIt, read the ECM DTCs.
Did this DTC set again?All
Ye s!Go To 2
No!Go To 6
2 Turn the ignition off.
Disconnect each Glow Plug harness connector.
Disconnect the Glow Plug Module harness connector.
Measure the resistance of each Glow Plug Control circuit.
Is the resistance below 10.0 ohms for each circuit?All
Ye s!Go To 3
No!Repair the appropriate Glow Plug Control circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
3 Turn the ignition off.
Disconnect each Glow Plug harness connector.
Disconnect the Glow Plug Module harness connector.
Measure the resistance between ground and each Glow Plug Control circuit.
Is the resistance below 1000.0 ohms for any of the measurements?All
Ye s!Repair the appropriate Glow Plug Control circuit for a short to
ground.
Perform ROAD TEST VERIFICATION - VER-2.
No!Go To 4
4 Turn the ignition off.
Disconnect each Glow Plug harness connector.
Disconnect the Glow Plug Module harness connector.
Turn the ignition on.
Measure the voltage of each Glow Plug Control circuit.
Is the voltage below 1.0 volt for each circuit?All
Ye s!Go To 5
No!Repair the appropriate Glow Plug Control circuit for a short to
voltage
Perform ROAD TEST VERIFICATION - VER-2.
83
DRIVEABILITY - DIESEL
P1482-GLOW PLUG MODULE - EXCESS CURRENT ÐContinued

Symptom List:
P1482-GLOW PLUG MODULE - INCORRECT TIMER
P1482-GLOW PLUG MODULE - INTERNAL FAULT
P2538-GLOW PLUG MODULE COMMUNICATION ERROR
P2538-GLOW PLUG MODULE EXCESSIVE CURRENT ERROR
P2538-GLOW PLUG MODULE TIMER ERROR
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be P1482-GLOW PLUG MODULE -
INCORRECT TIMER.
POSSIBLE CAUSES
GLOW PLUG MODULE
INTERMITTENT CONDITION
TEST ACTION APPLICABILITY
1NOTE: If the ECM detects and stores a DTC, the ECM also stores the
engine/vehicle operating conditions under which the DTC was set. Some of
these conditions are displayed on the DRB at the same time the DTC is
displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to
duplicate these conditions may assist when checking for an active DTC.
NOTE: This DTC indicates an internal Glow Plug Control Module problem
or an incorrect Glow Plug Module has been installed.
Turn the ignition on.
With the DRBIIIt, erase ECM DTCs.
Perform several engine run cycles, turning the ignition off for at least 20 seconds
between each engine run cycle.
With the DRBIIIt, read the ECM DTCs.
Did this DTC set again?All
Ye s!Replace and program the Glow Plug Control Module in accor-
dance with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
No!Go To 2
85
DRIVEABILITY - DIESEL

Symptom:
P1610-ENGINE CONTROL RELAY PLAUSIBILITY
When Monitored and Set Condition:
P1610-ENGINE CONTROL RELAY PLAUSIBILITY
When Monitored: During after-run.
Set Condition: The internal ECM timer determines that the Engine Control Relay
remains on for more than 2.0 seconds after the ECM has turned off the Engine Control
Relay.
POSSIBLE CAUSES
CHECK FOR OTHER DTCS
CHECK THE ECM POWER AND GROUNDS
ENGINE CONTROL MODULE
INTERMITTENT CONDITION
SUBSTITUTE ENGINE CONTROL RELAY
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRB, check for additional DTCs.
Are other DTCs present?All
Ye s!Refer to the Symptom List for diagnosis of the other DTCs before
continuing.
Perform ROAD TEST VERIFICATION - VER-2.
No!Go To 2
2NOTE: If the ECM detects and stores a DTC, the ECM also stores the
engine/vehicle operating conditions under which the DTC was set. Some of
these conditions are displayed on the DRB at the same time the DTC is
displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to
duplicate these conditions may assist when checking for an active DTC.
Turn the ignition on.
With the DRB, erase ECM DTCs.
Perform several ignition key cycles, pausing for at least 10 seconds between each
cycle.
Turn the ignition on.
With the DRB, read ECM DTCs.
Did this DTC set again?All
Ye s!Go To 3
No!Go To 5
87
DRIVEABILITY - DIESEL

Symptom:
P1610-ENGINE CONTROL RELAY SHUTS OFF TOO EARLY
When Monitored and Set Condition:
P1610-ENGINE CONTROL RELAY SHUTS OFF TOO EARLY
When Monitored: During after-run.
Set Condition: The internal ECM timer determines that the Engine Control Relay has
shut off before the AFTER-RUN mode of operation has been completed.
POSSIBLE CAUSES
CHECK FOR OTHER DTCS
INTERMITTENT CONDITION
SUBSTITUTE ENGINE CONTROL RELAY
ENGINE CONTROL RELAY CONTROL CIRCUIT OPEN INTERMITTENTLY
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRB, check for additional DTCs.
Are other DTCs present?All
Ye s!Refer to the Symptom List for diagnosis of the other DTCs before
continuing.
Perform ROAD TEST VERIFICATION - VER-2.
No!Go To 2
2NOTE: If the ECM detects and stores a DTC, the ECM also stores the
engine/vehicle operating conditions under which the DTC was set. Some of
these conditions are displayed on the DRB at the same time the DTC is
displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to
duplicate these conditions may assist when checking for an active DTC.
Turn the ignition on.
With the DRB, erase ECM DTCs.
Perform several ignition key cycles, pausing for at least 10 seconds between each
cycle.
Turn the ignition on.
With the DRB, read ECM DTCs.
Did this DTC set again?All
Ye s!Go To 3
No!Go To 5
89
DRIVEABILITY - DIESEL

Symptom:
P1610-ENGINE CONTROL RELAY SHUTS OFF TOO LATE
When Monitored and Set Condition:
P1610-ENGINE CONTROL RELAY SHUTS OFF TOO LATE
When Monitored: During after-run.
Set Condition: The internal ECM timer determines that the Engine Control Relay
remains on for more than 2.0 seconds after the ECM has turned off the Engine Control
Relay.
POSSIBLE CAUSES
CHECK FOR OTHER DTCS
INTERMITTENT CONDITION
SUBSTITUTE ENGINE CONTROL RELAY
ENGINE CONTROL RELAY CONTROL CIRCUIT SHORTED TO GROUND INTERMITTENTLY
ENGINE CONTROL RELAY OUTPUT CIRCUIT SHORTED TO VOLTAGE
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRB, check for additional DTCs.
Are other DTCs present?All
Ye s!Refer to the Symptom List for diagnosis of the other DTCs before
continuing.
Perform ROAD TEST VERIFICATION - VER-2.
No!Go To 2
2NOTE: If the ECM detects and stores a DTC, the ECM also stores the
engine/vehicle operating conditions under which the DTC was set. Some of
these conditions are displayed on the DRB at the same time the DTC is
displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to
duplicate these conditions may assist when checking for an active DTC.
Turn the ignition on.
With the DRB, erase ECM DTCs.
Perform several ignition key cycles, pausing for at least 10 seconds between each
cycle.
Turn the ignition on.
With the DRB, read ECM DTCs.
Did this DTC set again?All
Ye s!Go To 3
No!Go To 6
91
DRIVEABILITY - DIESEL

Symptom:
P1611-SENSOR SUPPLY 1 VOLTAGE IS TOO HIGH
When Monitored and Set Condition:
P1611-SENSOR SUPPLY 1 VOLTAGE IS TOO HIGH
When Monitored: With the ignition on.
Set Condition: The ECM detects a short to voltage on the APP Sensor 5-volt Supply
circuit or the CMP Sensor 5-volt Supply circuit.
POSSIBLE CAUSES
VISUAL WIRING AND CONNECTOR INSPECTION
INTERMITTENT CONDITION
SENSOR SUPPLY 1 SHORTED TO VOLTAGE
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1NOTE: If the ECM detects and stores a DTC, the ECM also stores the
engine/vehicle operating conditions under which the DTC was set. Some of
these conditions are displayed on the DRB at the same time the DTC is
displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to
duplicate these conditions may assist when checking for an active DTC.
Turn the ignition on.
With the DRB, erase ECM DTCs.
Turn the ignition off for 10 seconds.
Start the engine.
Monitor the DRB for ECM DTCs.
Did this DTC set again?All
Ye s!Go To 2
No!Go To 4
2 Turn the ignition off.
Visually inspect the wiring and connectors associated with the APP and CMP Sensors
for problems that may result in a short circuit.
Were any problems found?All
Ye s!Repair or replace wiring/connectors as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No!Go To 3
94
DRIVEABILITY - DIESEL

Symptom:
P1611-SENSOR SUPPLY 1 VOLTAGE IS TOO LOW
When Monitored and Set Condition:
P1611-SENSOR SUPPLY 1 VOLTAGE IS TOO LOW
When Monitored: With the ignition on.
Set Condition: The ECM detects a short to ground on the APP Sensor 5-volt Supply
circuit or the CMP Sensor 5-volt Supply circuit.
POSSIBLE CAUSES
APP SENSOR
CMP SENSOR
VISUAL WIRING AND CONNECTOR INSPECTION
INTERMITTENT CONDITION
SENSOR SUPPLY 1 SHORTED TO GROUND
ACCEL PEDAL POSITION SENSOR 5-VOLT SUPPY CIRCUIT SHORT TO SENSOR GROUND CIR-
CUIT
CAMSHAFT POSITION SENSOR 5-VOLT SUPPLY CIRCUIT SHORTED TO SENSOR GROUND
CIRCUIT
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1NOTE: If the ECM detects and stores a DTC, the ECM also stores the
engine/vehicle operating conditions under which the DTC was set. Some of
these conditions are displayed on the DRB at the same time the DTC is
displayed.
NOTE: Before erasing stored DTCs, record these conditions. Attempting to
duplicate these conditions may assist when checking for an active DTC.
Turn the ignition on.
With the DRB, erase ECM DTCs.
Turn the ignition off for 10 seconds.
Turn the ignition on.
Monitor the DRB for ECM DTCs.
Did this DTC set again?All
Ye s!Go To 2
No!Go To 8
2 Turn the ignition off.
Visually inspect the wiring and connectors associated with the APP and CMP Sensors
for problems that may result in a short circuit.
Were any problems found?All
Ye s!Repair or replace wiring/connectors as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No!Go To 3
96
DRIVEABILITY - DIESEL