0513437 JOHNSON SEAL

Table 1
J1939 Code and Description CDL Code and Description Comments
91-8
Accelerator Pedal Position #1 : Abnormal Frequency, Pulse Width, or Period 91-8
Throttle Position Sensor : Abnormal Frequency, Pulse Width, or Period The 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 and a default value is used. The engine speed is limited to high idle. The throttle position sensor is mounted to a pedal assembly that allows the operator to control the speed of the engine. The geometry of the pedal assembly 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 throttle pedal. The throttle position sensor produces a minimum duty cycle in the released position and a maximum duty cycle in the fully depressed position. When the pedal is released, the ECM translates the sensor output signal to a throttle position of 0 percent. When the pedal is fully depressed, the ECM translates the output signal to a throttle position of 100 percent.
Table 2
Recommended Tools
146-4080 Digital Multimeter Gp
7X-1710 Multimeter Probe
326-4904 Adapter Cable As
Table 3
Troubleshooting Test Steps Values Results
1. Check the Signal Frequency and the Duty Cycle at the Sensor
A. Turn the keyswitch to OFF.
B. Remove the wire from terminal location C (throttle position) on the harness side of the connector for the throttle position sensor.
C. Install a 326-4904 Adapter Cable As (3-PIN BREAKOUT) at the connector for the throttle position sensor.
D. Connect the connector for the throttle position sensor.
E. Turn the keyswitch to ON.
F. Measure the frequency and the duty cycle between terminal B (digital return) and terminal C (throttle position) at the 326-4904 Adapter Cable As (3-PIN BREAKOUT). Operate the throttle pedal while making the measurements.
Turn the keyswitch to the OFF position.
Remove the breakout harness. Restore the wiring for the harness connector to the original configuration.
Frequency and Duty Cycle
Result: The frequency and the duty cycle are within specifications for the entire range of the pedal.
Repair: Repair the harness or replace the harness. Verify that the problem is resolved.
Result: The ECM detects an incorrect frequency on the throttle signal or an incorrect duty cycle on the throttle signal. The frequency is below 150 Hz or the frequency is above 1000 Hz. The duty cycle is less than 5 percent or the duty cycle is greater than 95 percent.
Proceed to Test Step 2.
2. Check the Supply Voltage to the Sensor
A. Turn the keyswitch to OFF.
B. Disconnect the harness connector for the throttle position sensor.
C. Measure the voltage across terminal A (8 V supply) and terminal B (digital return) on the harness side of the connector.
7.5 VDC
Result: The supply voltage is above 7.5 VDC at the sensor connector.
Repair: The wiring is OK. Replace the sensor. Verify that the problem is resolved.
Result: The supply voltage is not above 7.5 VDC at the sensor connector. The supply voltage is not reaching the speed control.
Repair: Repair the harness wiring or replace the harness. Verify that the problem is resolved.
If this procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solution Network (DSN).