EDGE-CUTTING 4T2922 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the throttle position sensor or if the diagnostic code in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table    
Code and Description     Conditions which Generate this Code     System Response    
91-8 Throttle Position Sensor : Abnormal Frequency, Pulse Width, or Period     The Electronic Control Module (ECM) detects an incorrect duty cycle on the throttle signal.     The code is logged. The ECM flags the throttle position as invalid data and a default value of zero percent is used. The engine speed is limited to low idle.    The throttle position sensor provides the throttle signal to the ECM. The throttle position sensor is mounted to a mechanism that allows the operator to control the speed of the engine. The geometry of the mechanism controls both the travel of the sensor and the range of the output signal. The throttle position sensor cannot be adjusted.The output from the throttle position sensor is a PWM signal that varies with the position of the mechanism. The throttle position sensor produces a minimum duty cycle in the deactivated position and a maximum duty cycle in the fully activated position. When the throttle is deactivated, the ECM translates the sensor's output signal to a throttle position of 0 percent. When the throttle is fully activated, the ECM translates the output signal to a throttle position of 100 percent.
Illustration 1 g01429530
Schematic for the throttle position sensorTest Step 1. Inspect the Electrical Connectors and the Wiring
Remove electrical power from the ECM.
Illustration 2 g01139425
ECM (1) J1/P1 connectors (2) J2/P2 connectors
Thoroughly inspect the J1/P1 and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01429547
P1 ECM connector (P1-6) +Battery (P1-37) Throttle position
Illustration 4 g01159881
Connector for the throttle position sensor (A) +Battery (B) Return (C) Throttle position
Perform a 45 N (10 lb) pull test on each of the wires in the circuit.
Check the allen head screw from each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque value.
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All of the connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - The connectors and/or wiring are not OK.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.STOPTest Step 2. Check the Status for "Throttle Position"
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Restore electrical power to the ECM.
Observe the status for "Throttle Position" on Cat ET while you operate the throttle control through the entire range of travel.Expected