SHAFT 4N3944 - Caterpillar

Table 1
J1939 Code and Description CDL Code and Description Comments
91-3
Accelerator Pedal Position 1 : Voltage Above Normal 91-3
Throttle Position Sensor : Voltage Above Normal The Electronic Control Module (ECM) detects signal voltage that is not in the acceptable range.
The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle.
The code is logged.
91-4
Accelerator Pedal Position 1 : Voltage Below Normal 91-4
Throttle Position Sensor : Voltage Below Normal The ECM detects signal voltage that is not in the acceptable range.
The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle.
The code is logged.
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 signal voltage that is not in the acceptable range.
The ECM flags the throttle position as invalid data and a default value is used. The engine speed is limited to high idle.
The code is logged. Note: Performing steps within this procedure requires the use of a multimeter capable of measuring a PWM duty cycle and frequency.
Table 2
Required Tools
Part Number Part Name Qty
7X-1710 Multimeter Probe 1
146-4080 Digital Multimeter Gp 1
326-4904 Adapter Cable As 1
Table 3
Troubleshooting Test Steps Values Results
1. Check the Signal Frequency and the Duty Cycle at the Sensor
A. Turn the keyswitch to the OFF position.
B. Remove the wire from terminal location C (throttle position) on the wiring 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 the ON position.
F. Measure the frequency and the duty cycle at the 326-4904 Adapter Cable As (3-PIN BREAKOUT) between the following terminals:
- B (digital return) and C (throttle position)
G. Operate the throttle pedal while making the measurements.
H. Turn the keyswitch to the OFF position.
J. Remove the breakout harness.
K. Restore the wiring harness connector to the original configuration.
Frequency
Duty cycle
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.
Result: The frequency and the duty cycle are within specifications for the entire range of the pedal.
Repair: Repair or replace the wiring harness.
If the problem is not resolved, proceed to Test Step 2.
2. Check the Supply Voltage to the Sensor
A. Turn the keyswitch to the OFF position.
B. Disconnect the wiring harness connector for the throttle position sensor.
C. Measure the voltage across the following wiring harness connector terminals:
- A (8 V supply) and B (digital return)
7.5 VDC
Result: