TEST ACTION APPLICABILITY
2 Turn the ignition on.
With the DRBIIIt, erase ECM DTCs.
Turn the ignition on and off several times pausing 10 seconds between each key cycle.
With the DRBIIIt, read the ECM DTCs.
Are any P1685 DTCs present?All
Ye s®Go To 3
No®Go To 4
3 Replace and program the SKIM in accordance with the Service Information.
Turn the ignition on.
With the DRBIIIt, erase ECM DTCs.
Turn the ignition on and off several times pausing for 10 seconds between key cycles.
With the DRBIIIt, read ECM DTCs.
Are there any P1685 DTC's present?All
Ye s®Replace and program the ECM in accordance with the Service
Information.
Perform ROAD TEST VERIFICATION - VER-2.
No®Test Complete.
4WARNING: 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.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
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 ROAD TEST VERIFICATION - VER-2.
No®Test Complete.
169
DRIVEABILITY - DIESEL
P1685-SKIM SYSTEM INVALID KEY CODE RECEIVED ÐContinued
Symptom List:
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY
WITH BRAKE SWITCH
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY
WITH POTENTIOMETER
P2120-ACC PEDAL POSITION SENSOR 1 CKT SIGNAL VOLTAGE
TOO HIGH
P2120-ACC PEDAL POSITION SENSOR 1 CKT SIGNAL VOLTAGE
TOO LOW
P2120-ACC PEDAL POSITION SENSOR 1 CKT SUPPLY VOLTAGE
TOO HIGH OR LOW
Test Note: All symptoms listed above are diagnosed using the same tests.
The title for the tests will be P2120-ACC PEDAL POSITION
SENSOR 1 CKT PLAUSIBILITY.
When Monitored and Set Condition:
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY
When Monitored: With the ignition on.
Set Condition: The Accelerator Pedal Position Sensor Signal is below 2% or above 21%
and the idle switch is not in the correct state. NOTE: The idle switch is designed to
transition when the accel position is approximately 16% (1.00 volt). This code sets the ECM
to Limp-in Mode, which includes a fixed engine speed of 1100 RPM.
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY WITH BRAKE
SWITCH
When Monitored: With the ignition on.
Set Condition: The ECM detects the Accelerator Pedal and the Brake Pedal have been
depressed at the same time for longer than the allowable time.
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY WITH POTENTI-
OMETER
When Monitored: With the ignition on.
Set Condition: The Accelerator Pedal Position Sensor Signal is below 0.20 volts, the idle
switch transitions at too high a percentage intermittently or the idle switch is not in the
correct state intermittently. NOTE: The idle switch is designed to transition when the accel
position is approximately 16% (1.00 volt). This code sets the ECM to Limp-in Mode, which
includes a fixed engine speed of 1100 RPM.
170
DRIVEABILITY - DIESEL
TEST ACTION APPLICABILITY
9 Turn the ignition on.
With the DRB III, read the PEDAL OUTPUT VOLTS.
With the accelerator pedal in the idle position, slowly depress the accelerator pedal
until the pedal is fully depressed.
NOTE: The PEDAL OUTPUT VOLTS should increase smoothly as the pedal
is depressed.
Does the voltage increase smoothly with the accelerator pedal travel?All
Ye s®Go To 10
No®Replace the Accelerator Pedal Position Sensor in accordance with
the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
10 Turn the ignition on.
With the DRB III, select Engine and with the custom display feature select Low Idle
Switch input and the Accel Pedal %.
Slowly depress and release the accelerator pedal several times while monitoring the
DRB III display.
NOTE: The Low Idle Switch state should change between 5% and 10% of
Accelerator Pedal position.
Did the Low Idle Switch state change between 5% and 10% of Accelerator Pedal
position?All
Ye s®Go To 11
No®Replace the Accelerator Pedal Position Sensor.
Perform ROAD TEST VERIFICATION - VER-2.
11WARNING: 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.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running and at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
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 ROAD TEST VERIFICATION - VER-2.
No®Test Complete.
12 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the APP Sensor Signal circuit.
Is the resistance below 10.0 ohms?All
Ye s®Go To 13
No®Repair the APP Sensor Signal circuit for an open
Perform ROAD TEST VERIFICATION - VER-2.
174
DRIVEABILITY - DIESEL
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY ÐContinued
TEST ACTION APPLICABILITY
13 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the APP Sensor Signal circuit.
Is the resistance below 1000 ohms?All
Ye s®Repair the APP Sensor Signal circuit for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 14
14 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between the APP Sensor Signal circuit and the Sensor
Ground circuit at of the APP Sensor harness connector.
Is the resistance below 1000 ohms?All
Ye s®Repair the APP Sensor Signal and Sensor Ground circuits for a
short together.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 15
15 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
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 APP Sensor Signal circuit.
Is the voltage above 1.0 volt?All
Ye s®Repair the APP Sensor Signal circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
16 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the 5-volt Supply circuit.
Is the resistance below 10.0 ohms?All
Ye s®Go To 17
No®Repair the 5-volt Supply circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
175
DRIVEABILITY - DIESEL
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY ÐContinued
TEST ACTION APPLICABILITY
17 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between the 5-volt Supply circuit and the Sensor Ground
circuit at the APP Sensor harness connector.
Is the resistance above 1000 ohms for both of the measurements?All
Ye s®Go To 18
No®Repair the 5-volt Supply circuit for a short to the Sensor Ground
circuit.
Perform ROAD TEST VERIFICATION - VER-2.
18 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the 5-volt Supply circuit.
Is the resistance below 1000 ohms?All
Ye s®Repair the 5-volt Supply circuit for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 19
19 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
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 5-volt Supply circuit in the ECM harness connector.
Is the voltage above 1.0 volt?All
Ye s®Repair the 5-volt Supply circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
20 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the Low Idle Position Switch Sense circuit.
Is the resistance below 10.0 ohms?All
Ye s®Go To 21
No®Repair the Low Idle Position Switch Sense circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
176
DRIVEABILITY - DIESEL
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY ÐContinued
TEST ACTION APPLICABILITY
25 Turn the ignition off.
Disconnect the APP Sensor harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the Low Idle Switch Sensor Ground circuit between the
APP Sensor and the ECM.
Is the resistance below 10.0 ohms?All
Ye s®Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
No®Repair the Low Idle Switch Sensor Ground circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
178
DRIVEABILITY - DIESEL
P2120-ACC PEDAL POSITION SENSOR 1 CKT PLAUSIBILITY ÐContinued
Symptom:
*CHECKING THE BOOST PRESSURE SENSOR CALIBRATION
POSSIBLE CAUSES
TURBOCHARGER BOOST PRESSURE SENSOR CALIBRATION
TEST ACTION APPLICABILITY
1 Allow the engine to idle.
With the DRB, select Engine, Bosch then Sensors. Read the Boost Pressure Voltage.
Is the Boost Pressure Voltage between 1.50 and 2.00 volts?All
Ye s®Test Complete.
No®Replace the Turbocharger Boost Pressure Sensor.
Perform ROAD TEST VERIFICATION - VER-2.
182
DRIVEABILITY - DIESEL
Symptom:
*CHECKING THE EGR SYSTEM
POSSIBLE CAUSES
ECM/PCM RELAY OUTPUT CIRCUIT OPEN
EGR SOLENOID CONTROL CIRCUIT OPEN
EGR VALVE
VACUUM SUPPLY HOSE
TEST ACTION APPLICABILITY
1 Disconnect the Vacuum Supply Hose at the EGR solenoid.
Connect a vacuum gauge to the Vacuum Supply Hose.
Start the engine and allow the engine to idle.
Is the vacuum above 10 inches of mercury at idle?All
Ye s®Go To 2
No®Repair leaking or restricted Vacuum Supply Hose or faulty
Vacuum Supply Pump.
Perform ROAD TEST VERIFICATION - VER-2.
2 Turn the ignition off.
Disconnect the EGR Solenoid harness connector.
Turn the ignition on.
Using a 12-volt test light connected to ground, check the ECM/PCM Relay Output
circuit at the EGR Solenoid harness connector.
Is the test light on?All
Ye s®Go To 3
No®Repair the ECM/PCM Relay Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
3 Turn the ignition off.
Disconnect the EGR Solenoid harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the EGR Solenoid Control circuit.
Is the resistance below 10.0 ohms?All
Ye s®Go To 4
No®Repair the EGR Solenoid Control circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
4NOTE: The Vacuum Output Hose must not be leaking or restricted for the
result of this test to be valid.
Turn the ignition off.
Disconnect the Vacuum Supply and Vacuum Output Hoses in the EGR Solenoid
vacuum connector.
Connect the Vacuum Supply Hose to the Vacuum Output Hose.
Test drive the vehicle and observe vehicle performance.
Is there a power reduction on vehicle acceleration?All
Ye s®Test Complete.
No®Replace the EGR Valve.
Perform ROAD TEST VERIFICATION - VER-2.
185
DRIVEABILITY - DIESEL