ENGINE AR-PRIMARY 4551491 - Caterpillar

Illustration 1 g03372576
Schematic of the Accelerator Pedal Position Sensor
This diagnostic code is associated with the Accelerator Pedal position sensor circuit. The FMI 08 means that the ECM has determined that the signal frequency or the signal pulse width is not within the expected range.The Accelerator Pedal position control has an output frequency of approximately 500 Hz. The duty cycle of the signal changes as the Accelerator Pedal pedal position is changed. The duty cycle increases as the Accelerator Pedal pedal position is changed. Valid values range from 5% to 95% duty cycle.The possible causes of this diagnostic code are listed:
The Accelerator Pedal sensor has failed.
Intermittent connections or poor connections
Mechanical devices are loose.
The ECM has failed. The ECM is unlikely to fail.System Response:The diagnostic code will generate a level 2 warning. Underspeed Control will be disabled and the hystat transmission will be limited to low speed.Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 2795 FMI 08 is active before performing this procedure.Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.Test Step 1. Check For Power At The Sensor
Do not disconnect the harness connector from the joystick.
Turn the key start switch to the ON position.
At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the voltage supply wire 308-YL(Yellow) (contact C) and along the return wire 200-BK(Black) (contact B).
Measure the voltage from contact C (wire 308-YL(Yellow)) to contact B (wire 200-BK(Black)). Expected Result:The voltage is approximately 8.0 1.0 DCV.Results:
OK - The voltage is approximately 8.0 1.0 DCV. Proceed to Test Step 3.
NOT OK - The measurement is not correct.Repair: Repair the machine harness or replace the machine harness.STOPTest Step 2. Check The Signal Circuit For A Short In The Harness
Disconnect the negative battery cable and turn the key start switch to the OFF position.
Disconnect the machine harness connectors from the sensor and the ECM.
Measure the resistance between contact J1-38 (wire R914-OR(Orange)) and all contacts that are used in the J1 harness connectors. Expected Result:The resistance is greater than 5000 ohms.Results:
OK - The resistance is greater than 5000 ohms. The circuit is correct. Proceed to Test Step 3.
NOT OK - The resistance is less than 5 ohms. The signal circuit is shorted to another circuit in the harness.Repair: Repair the machine harness or replace the machine harness.STOPTest Step 3. Check The Signal Circuit Of The Sensor For The Correct Frequency
The key start switch remains in the OFF position.
At the back of the harness connector for the sensor, remove the 7X-1710 Multimeter Probe from contact C (wire 308-YL(Yellow)) and insert the probe along the signal wire R914-OR(Orange) (contact F).
At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the ground wire 200-BK(Black) (contact B).
Reconnect the negative battery cable and turn the key start switch to