System Operation Description:
Accelerator Pedal Position Sensor
The accelerator pedal position sensor is used to provide a throttle position signal to the ECM. Sensor
output is a constant frequency signal with a pulse width that varies with the pedal position. This output
signal is referred to as either a duty cycle or a pulse width modulated signal (PWM) and this output signal is expressed as a percentage between 3 and 100 percent.
The pedal mounted accelerator pedal position sensor is attached directly to the accelerator pedal assembly and the pedal mounted accelerator pedal position sensor requires no adjustment.
The accelerator pedal position sensor will produce a duty cycle of 10 to 22 percent at low idle and 75
to 90 percent when the accelerator pedal is fully depressed. The percent of duty cycle is translated in the ECM into an accelerator pedal position of 3 to 100 percent.
The accelerator pedal position sensor is powered by the ECM supply voltage (+8 VDC) from connector
P1:4 to terminal “A” of the accelerator pedal position sensor connector. The accelerator pedal position
sensor can be replaced separately from the pedal assembly. An incorrectly calibrated pedal assembly
can not be adjusted. The entire pedal assembly must be replaced.
If the vehicle is using the ECM dedicated PTO functions, the accelerator pedal position sensor will
be ignored while the engine is in PTO mode and the “PTO Configuration” is programmed to one of the following parameters:
• Remote Switches
• Remote Throttle
Note: In the cab switches configuration, the cab accelerator pedal can be used in order to control
the engine rpm for the PTO operation. The cab accelerator pedal can also be ignored in the “Cab
Switches” PTO configuration. Programming of customer parameters is required in order to ignore
the cab accelerator pedal in the “Cab switches” configuration.
The ECM is in PTO mode if the “PTO On/Off Switch” is on. This can be checked with the electronic service tool. Refer to Troubleshooting, “PTO Switch Circuit – Test” for testing if the PTO is being used.
Test Step 1. Monitor the Status for the “Accelerator Pedal Position”
A. Connect the electronic service tool to the data link connector.
B. Turn the key switch to the ON position.
C. Access the status for the “Accelerator Pedal Position”.
D. While the status is monitored, depress the accelerator pedal and release the accelerator pedal.
Expected Result:
The status for the “Accelerator Pedal Position” is 100% when the accelerator is fully depressed. The
status for the “Accelerator Pedal Position” is 0% when the accelerator is fully released.
Results:
• OK – The accelerator pedal position sensor is operating correctly.
Repair: If the problem is intermittent, refer to Troubleshooting, “Electrical Connectors – Inspect”.
Verify that the engine is not in PTO mode. PTO mode may cause the accelerator pedal position sensor to be ignored.
Verify that all required parameters are programmed. Certain unprogrammed parameters may cause the engine to be limited to low idle.
Refer to Troubleshooting, “System Configuration Parameters”.
STOP.
• Not OK – The accelerator pedal position sensor is not operating correctly. Proceed to Test Step 2.
Test Step 2. Monitor the Duty Cycle
A. Turn the key switch to the ON position.
B. Access the following display screen in order:
• “Service”
• “Calibrations”
• “Monitor Throttle Position Sensor”
C. While the duty cycle is being monitored, depress the accelerator pedal and release the accelerator pedal.
Expected Result:
The duty cycle is 10% to 22% when the accelerator pedal is released. The duty cycle is 75% to 90%
when the accelerator pedal is depressed.
Results:
• OK – The duty cycle is within the specified range.
Repair: If the problem is intermittent, refer to Troubleshooting, “Electrical Connectors – Inspect”.
Verify that the engine is not in PTO mode. PTO mode may cause the accelerator pedal position
sensor to be ignored.
Verify that all required parameters are programmed. Certain unprogrammed parameters
may cause the engine to be limited to low idle.
Refer to Troubleshooting, “System Configuration Parameters”.
STOP.
• Not OK – The duty cycle is not within the range.
Proceed to Test Step 3.
Test Step 3. Inspect Electrical Connectors and Wiring
A. Thoroughly inspect the J1/P1 ECM connector, the firewall bulkhead connector and the
accelerator pedal position sensor connector.
Refer to Troubleshooting, “Electrical Connectors – Inspect” for details.
B. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the accelerator pedal position sensor:
• P1:3
• P1:4
• P1:5
• P1:66
C. Check the ECM connector (Allen Head Screw) for the proper torque of 6.0 N·m (55 lb in).
D. Check the harness and wiring for abrasion and pinch points from the accelerator pedal position
sensor to the ECM.
Expected Result:
All connectors, pins and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion or pinch points.
Results:
• OK – Proceed to Test Step 4.
• Not OK
Repair: Perform the following repair:
Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the
seals are properly in place and ensure that the connectors are completely coupled.
Verify that the repair eliminates the problem.
STOP.
Test Step 4. Check for Active Diagnostic Codes
A. Turn the key switch to the ON position.
B. Check for active diagnostic codes on the electronic service tool.
Note: When the ECM automatically calibrates new duty cycle values for the low idle throttle position
and the high idle throttle position the ECM assumes 22 percent duty cycle at low idle and 75 percent
duty cycle at high idle. As a result, you may notice that the throttle position status reaches 100 percent well before the accelerator pedal is fully depressed.
This is normal. After some cycling of the accelerator pedal to the high idle position, the ECM will adjust
the calibration automatically. The ECM will adjust the calibration automatically provided that the high
idle stop position is within the 75 to 90 percent duty cycle range, and the low idle is in the 10 to 22
percent duty cycle range. During normal operation, you may also notice that more movement of the
accelerator pedal is required for the throttle position status to increase above 3 percent. You may also
observe that the status reaches the 100 percent value prior to the limit of the high idle position. This
is done in order to ensure that the throttle reaches these two critical points for engine operation.
Expected Result:
Result 1 91-08 or 91-13 is Active.
Result 2 41-03 is Active.
Result 3 41-04 is Active.
Results:
• Result 1 – Proceed to Test Step 5.
• Result 2 – Proceed to Test Step 10.
• Result 3 – Proceed to Test Step 12.
Test Step 5. Check the Supply Voltage at the Sensor for the Accelerator Pedal Position Sensor
A. Install a breakout T with 3 terminals at the accelerator pedal position sensor connector J403/P403.
B. Turn the key switch to the ON position.
C. Measure the voltage at terminal “A” (+8 V) with reference to terminal “B” (Accelerator/Switch Sensor Common).
Expected Result:
The measured voltage is between 7.5 VDC and 8.5 VDC for the pedal mounted throttle position sensor that is used in the cab.
Results:
• OK – Proceed to Test Step 6.
• Not OK – The sensor is not receiving the correct voltage.
Repair: Inspect the electrical connectors and wiring.
Repair the faulty wiring.
Verify that the repair eliminates the problem.
STOP.
Test Step 6. Check the Duty Cycle at the Sensor
Note: Performing certain steps within this procedure requires the use of a multimeter that is capable of measuring a PWM duty cycle.
A. Turn the key switch to the OFF position.
B. Remove the signal wire for the accelerator pedal position sensor (terminal “C”) from P403. This is the harness side of the accelerator pedal position sensor connector.
C. Install a breakout T with 3 terminals between the J403 and the P403 Accelerator pedal position sensor connector.
D. Connect the multimeter probes to terminal “C” (Accelerator Pedal Position) and terminal “B” (Accelerator/Switch Sensor Common) of the breakout T.
E. While the duty cycle is being monitored on the multimeter, depress the accelerator pedal and
release the accelerator pedal.
Expected Result:
The duty cycle is between 10% and 22% when the accelerator pedal is fully released. The duty cycle is between 75% and 90% when the accelerator pedal is fully depressed.
Results:
• OK – The accelerator pedal position sensor is working correctly.
Repair: Insert the signal wire into terminal C of the P403 connector.
Proceed to Test Step 7.
• Not OK – Leave the PWM probe connected to the breakout T. Insert the wire (terminal C) into
the vehicle harness connector. The accelerator pedal position sensor or the accelerator pedal assembly is faulty. Proceed to Test Step 8.
Test Step 7. Check the Duty Cycle of the Accelerator Pedal Position Sensor at the ECM
Note: Performing certain steps within this procedure requires the use of a multimeter that is capable of
measuring a PWM duty cycle.
A. Turn the key switch to the OFF position.
B. Remove the wire for the accelerator pedal position sensor P1:66.
Note: You may be required to disconnect the P1 ECM connector in order to remove the terminal for the signal input of the accelerator pedal position sensor.
C. Connect the multimeter probes between the removed wire and P1:5 (Accelerator/Switch Sensor Common).
D. Reconnect the P1 ECM connector to the ECM.
E. Turn the key switch to the ON position.
F. While the duty cycle output of the accelerator pedal position sensor is being monitored on the multimeter, depress the accelerator pedal and release the accelerator pedal.
G. Turn the key switch to the OFF position.
H. Reinsert the signal wire into P1:66 of the P1 ECM connector.
Expected Result:
The duty cycle is between 10% and 22% when the accelerator pedal is fully released. The duty cycle is between 75% and 90% when the accelerator pedal is fully depressed.
Results:
• OK – A good signal from the accelerator pedal position sensor is reaching the ECM. Verify that
the ECM is receiving the proper battery voltage. If the ECM is receiving the proper battery voltage,
temporarily connect a test ECM and verify that the problem is resolved. If the problem disappears
with the test ECM, reconnect the suspect ECM.
If the problem returns with the suspect ECM, replace the ECM. STOP.
• Not OK – There is a problem with signal wire for the accelerator pedal position sensor in the
vehicle wiring harness. Proceed to Test Step 9.
Test Step 8. Remove the Accelerator Pedal Position Sensor from the Accelerator Pedal Assembly
A. Turn the key switch to the OFF position.
B. Remove the accelerator pedal position sensor from the accelerator pedal assembly. Note sensor orientation in the accelerator pedal assembly, and the sensor pigtail routing prior to sensor removal. Thoroughly inspect the pigtail for signs of abrasion.
C. Connect the multimeter that is capable of measuring a PWM duty cycle to terminal “C” of
the breakout T.
D. Turn the key switch to the ON position.
E. Display the duty cycle output of the accelerator pedal position sensor while the sensor slot is released. Use a screwdriver to advance the
sensor slot to the maximum position. Refer to Illustration 32.
When the sensor is removed from the accelerator pedal assembly, the following diagnostic code
may be generated:
• 91-13 Throttle Sensor Calibration (28) This is normal. The diagnostic code should
disappear when the sensor is properly assembled back into the accelerator pedal assembly.
Expected Result:
When the sensor is removed from the accelerator pedal assembly and the sensor slot is released, the duty cycle is 10 percent or less. When the sensor slot is moved to the maximum position, the duty cycle increases to 90 percent or more.
Results:
• OK – The accelerator pedal position sensor is working correctly. Clear any diagnostic codes that
were caused by performing this test procedure.
Refer to the OEM dealer for correct replacement of the accelerator pedal assembly. STOP.
• Not OK – The accelerator pedal position sensor is faulty. Check the accelerator pedal assembly
in order to ensure that the accelerator pedal assembly is not causing damage to the sensor.
If the accelerator pedal assembly is causing damage to the sensor, refer to the OEM dealer for correct replacement of the accelerator pedal assembly. If the accelerator pedal assembly appears OK, replace the accelerator pedal position sensor. STOP.
Test Step 9. Route the Supply Bypass Wires to the Accelerator Pedal Position Sensor
A. Turn the key switch to the OFF position.
B. Remove the signal wire for the accelerator pedal position sensor from P1:66.
C. Remove terminal “C” (Accelerator Pedal Position) from the accelerator pedal position sensor connector.
D. Route new wiring from the ECM to the accelerator pedal position sensor.
E. Turn the key switch to the ON position.
F. Check the duty cycle of the accelerator pedal position sensor on the electronic service tool
while the accelerator pedal assembly is being moved over the full range.
Expected Result:
The duty cycle is between 10% and 22% when the accelerator pedal is fully released. The duty cycle is between 75% and 90% when the accelerator pedal is fully depressed.
Results:
• OK
Repair: Perform the following repair:
The wiring from the ECM to the accelerator pedal position sensor appears faulty. Permanently install new wiring.
Verify that the repair eliminates the problem.
STOP.
• Not OK – Double check the wiring, the J1/P1 ECM connector and the sensor connector. If a problem still exists, restart the test procedure.
STOP.
Test Step 10. Short the +8 Volt Supply at the Sensor
A. Turn the key switch to the Off position.
B. Connect a breakout T between the J403 and the P403 Accelerator Pedal Position Sensor connectors.
C. Insert a jumper wire between terminal A and terminal B of the breakout T.
D. Turn the key switch to the On position.
E. Check for active diagnostic codes on the electronic service tool.
Expected Result:
The 41-03 changes to 41-04 when the jumper wire is installed.
Results:
• OK – There is a problem with the accelerator pedal position sensor.
Repair: Remove the breakout T.
Temporarily connect a new sensor.
If the new sensor eliminates the problem, reconnect the suspect sensor.
If the problem returns, permanently replace the sensor.
Verify that the repair eliminates the problem.
STOP.
• Not OK – Proceed to Test Step 11. Test Step 11. Short the +8 Volt Supply at the ECM
A. Turn the key switch to the Off position.
B. Connect a 140-2266 Cable (Seventy-Pin Breakout) between the J1 and P1 ECM connectors.
C. Insert a jumper wire between terminal 4 and terminal 5 of the breakout T.
D. Turn the key switch to the On position.
E. Check for active diagnostic codes on the electronic service tool.
Expected Result:
The 41-03 changes to 41-04 when the jumper wire is installed.
Results:
• OK – There is a problem with the wiring between the ECM and the accelerator pedal position
sensor.
Repair: Remove the breakout T.
Inspect the wiring between the ECM and the sensor.
Repair the faulty wiring.
Verify that the repair eliminates the problem.
STOP.
• Not OK – There may be a problem with the ECM.
Repair: Remove the breakout T.
Temporarily connect a test ECM.
If the test ECM fixes the problem, reconnect the suspect ECM.
If the problem returns, permanently replace the ECM.
Verify that the repair eliminates the problem.
STOP.
Test Step 12. Disconnect the Sensor
A. Turn the key switch to the Off position.
B. Disconnect the J403/P403 Accelerator Pedal Position Sensor connector.
C. Turn the key switch to the On position.
D. Check for active diagnostic codes on the electronic service tool.
Expected Result:
The 41-04 changes to 41-03 when the jumper wire is installed.
Results:
• OK – There is a problem with the accelerator pedal position sensor.
Repair: Temporarily connect a new sensor.
If the new sensor eliminates the problem, reconnect the suspect sensor.
If the problem returns, permanently replace the sensor.
Verify that the repair eliminates the problem.
STOP.
• Not OK – Proceed to Test Step 13.
Test Step 13. Remove the +8 Volt Supply Wires from the ECM
A. Turn the key switch to the Off position.
B. Remove the wires from P1:4 and P1:5.
C. Turn the key switch to the On position.
D. Check for active diagnostic codes on the electronic service tool.
Expected Result:
The 41-04 changes to 41-03 when the wires are removed.
Results:
• OK – There is a problem with the wiring between the ECM and the accelerator pedal position
sensor.
Repair: Inspect the wiring between the ECM and the sensor.
Repair the faulty wiring.
Verify that the repair eliminates the problem.
STOP.
• Not OK – There may be a problem with the ECM.
Repair: Temporarily connect a test ECM.
If the test ECM fixes the problem, reconnect the suspect ECM.
If the problem returns, permanently replace the ECM.
Verify that the repair eliminates the problem.
STOP.
