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 one of the diagnostic codes in Table 2 is active or easily repeated.
Note: Some of the following codes may not be applicable for certain applications.
Note: Performing steps within this procedure requires the use of a multimeter capable of measuring a PWM duty cycle and frequency. Refer to Table 1 for the tools recommended for the procedure.
Recommended Tools | |
146-4080 Digital Multimeter Gp | |
7X-1710 Multimeter Probe | |
326-4904 Adapter Cable As |
Diagnostic Trouble Codes | |||
---|---|---|---|
J1939 Code | CDL Code | Code Description (code descriptions may vary) |
Comments |
29-2 | 774-2 | Accelerator Pedal Position 2 : Erratic, Intermittent, or Incorrect | The Electronic Control Module (ECM) has detected an invalid combination of positions for the multi-position switches. The code is logged. If equipped, the warning light will come on. Engine RPM defaults to a predetermined safe speed. The throttle switch is ignored by the ECM until the fault is cleared and the keyswitch is cycled. |
29-3 | 774-3 | Accelerator Pedal Position 2 : 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 is limited to high idle. |
29-4 | 774-4 | Accelerator Pedal Position 2 : 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 is limited to high idle. |
29-8 | 774-8 | Accelerator Pedal Position 2 : 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. |
91-2 | 91-2 | Accelerator Pedal Position 1 : Erratic, Intermittent, or Incorrect | The Electronic Control Module (ECM) has detected an invalid combination of positions for the multi-position switches. The code is logged. If equipped, the warning light will come on. Engine RPM defaults to a predetermined safe speed. The throttle switch is ignored by the ECM until the fault is cleared and the keyswitch is cycled. |
91-3 | 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 is limited to high idle. |
91-4 | 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 is limited to high idle. |
91-8 | 91-8 | Accelerator Pedal Position 1 : 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.
Illustration 1 g02075215
Schematic for throttle position sensor
Illustration 2 g01214474
P1 ECM connector
(P1-4) 8 VDC supply
(P1-5) Digital return
(P1-66) Throttle position