BOLT 1541582 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the circuit that is for the throttle position sensor. Also use this procedure if the diagnostic code in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
J1939 Code and Description Conditions that Generate the Code System Response
91-8 Accelerator Pedal Position 1 : Abnormal Frequency, Pulse Width, or Period The Electronic Control Module (ECM) detects an incorrect frequency on the throttle signal or an incorrect duty cycle on the throttle signal. The code is logged. The ECM flags the throttle position as invalid data. The load sharing module provides a throttle signal to the engine ECM. The output for rated speed is a pulse width modulated signal (PWM) at a constant frequency. The speed signal varies with the position of the speed adjust potentiometer. The output signal is referred to as a duty cycle or as a PWM signal. The output signal is expressed as a percentage between 0 and 100 percent for the speed adjust.Note: Desired speed can be adjusted from 1141 to 1621 rpm over the range of the PWM signal for a 50 Hz application. For a 60 Hz application, the desired speed can be adjusted from 1369 to 1945 rpm over the range of the PWM signal.The ECM calculates the desired engine rpm from the throttle signal and the droop signal. The throttle signal is valid when the duty cycle is in the range of 5 to 95 percent. If the ECM determines that the throttle signal is invalid, the engine rpm is set to rated speed and the droop percentage will be applied.
Illustration 1 g02738562
Schematic of the circuit for the speed control
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the main disconnect switch to the OFF position.
Illustration 2 g02721290
Location of the J1/P1 and the J2/P2 ECM connectors (typical engine view)
(1) J1/P1 ECM connector
(2) J2/P2 ECM connector
Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect all of the other connectors that are in the circuit. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g02739536
Terminal locations at the P1 ECM connector
(P1-66) Throttle signal
Illustration 4 g02739576
Terminal locations at the P2 ECM connector
(P2-92) Digital return
Illustration 5 g02739582
Terminal locations at the engine interface connector
(5) Digital return
(30) + Battery
(40) - Battery
(66) Throttle signal
Illustration 6 g02756096
Terminal locations at the power interface connector
(44) + Battery
(45) - Battery
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the engine interface connector that are associated with the circuit.
Check the allen head screw on each ECM connector and the engine interface connector for the proper torque. refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points. Expected Result:All connectors, pins, and sockets are coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion or of pinch points.Results:
OK - The connectors and wiring appear to be OK. Proceed