BUSHING 7C6617 - Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the speed control circuit. Or, use this procedure if one of the following diagnostic codes is active or easily repeated.
Table 1
J1939 Code and Description Conditions which Generate this Code System Response
91-3
Accelerator Pedal Position #1 : Voltage Above Normal The ECM detects signal voltage that is not in the acceptable range. The code is logged. The ECM flags the throttle position as invalid data and a default value is used. The engine speed may be limited to high idle.
91-4
Accelerator Pedal Position #1 : Voltage Below Normal The ECM detects signal voltage that is not in the acceptable range. The code is logged. The ECM flags the throttle position as invalid data and a default value is used. The engine speed may be limited to high idle.
91-8
Throttle Position Sensor abnormal frequency, pulse width, or period The Engines Electronic Control Module (ECM) detects a sensor frequency that is less than 150 Hz or a sensor frequency that is greater than 1000 Hz for two seconds.
or
The ECM detects a duty cycle that is less than 5 percent or a duty cycle that is greater than 95 percent for one second. The code is logged.
The throttle signal defaults to a zero percent duty cycle (low idle). The speed control is used to provide a throttle signal to the engine control. The output for rated speed is a pulse width modulated signal. The signal varies with the position of the speed adjust potentiometer. The output signal is expressed as a percentage between 0 and 100 percent for the speed adjust potentiometer.The ECM calculates the desired engine speed. The desired engine speed is produced by the signal from the rated speed setting. The rated speed signal is valid when the duty cycle is in the range of 5 to 95 percent. If the rated speed signal is invalid, the engine will be set to the low idle.Some applications may choose not to use the speed control. Some applications may use a load sharing unit. The unit is configured to provide the engine control with a rated speed signal. Some of these units cannot provide a signal until the engine is running. In these cases, perform troubleshooting while the engine is running.
Illustration 1 g06284645
Schematic of the circuit for the speed control
Table 2
Troubleshooting Test Steps Values Results
1. Inspect the Electrical Connectors and the Wiring
A. Turn the main disconnect switch to the OFF position.
B. Thoroughly inspect connectors (P1), and (P2). Inspect all the connectors in the harness from the engine interface connector to the speed control that is associated with the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
C. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors, the engine interface connector, and the connector for the EMCP that are associated with the circuit.
D. Check the torque of the allen head screws for each of the ECM connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect"