PISTON AS 2959689 - Caterpillar

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 following diagnostic codes is active or easily repeated.
Table 1
Diagnostic Codes Table
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 Electronic Control Module (ECM) detects an incorrect frequency on the throttle signal or an incorrect duty cycle on the throttle signal.
This code is used when the parameter for the "Desired Speed Input Configuration" is configured to "PWM". 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. The Electronic Control Module (ECM) can be configured to receive three different types of throttle signals for the engine throttle control:"CAN Input" - A J1939 signal is received via the CAN data link."PWM" - The Pulse Width Modulated signal (PWM) must be received via terminal P1-66 at the ECM connector. If direct fuel control mode is used on the engine, the PWM signal must be received via terminal P1-66 at the ECM connector."0 - 5 VDC" - This analog signal must be received via terminal P1-1 at the ECM connector.The signals must be present at the respective inputs in order for the signals to be received by the ECM.The ECM also allows a primary throttle and a secondary throttle to be configured for the engine. The type of signal that will be used for the primary throttle is configured by setting the "Desired Speed Input Configuration" parameter. The type of signal that will be used for the secondary throttle is configured by setting the "Secondary Desired Speed Input Configuration" parameter. Configuring both of these parameters to the same setting will invalidate the setting for the secondary throttle. For using an electronic external governor for engine control, the "Direct Fuel Control Mode" parameter must be enabled. The ECM input at P1-66 must be used for direct fuel control of the engine. Refer to Troubleshooting, "Direct Fuel Control Mode - Test" for details.For information on these parameters, refer to Troubleshooting, "Configuration Parameters". The ECM will utilize