0325074 JOHNSON BUSHING, Steering handle

Table 1
Diagnostic Codes
J1939 Code Description
91-8 Accelerator Pedal Position 1 : Abnormal Frequency, Pulse Width, or Period
91-13 Accelerator Pedal Position 1 : Calibration Required
644-8 Engine External Speed Command Input : Abnormal Frequency, Pulse Width, or Period
644-13 Engine External Speed Command Input : Calibration Required
678-3 ECU 8 Volts DC Supply : Voltage Above Normal
678-4 ECU 8 Volts DC Supply : Voltage Below Normal Background Information for the Accelerator Pedal Position SensorThe accelerator pedal position sensor provides a throttle position signal to the Engine Control Module (ECM). The sensor is attached directly to the accelerator pedal assembly. The sensor cannot be adjusted.The accelerator pedal position sensor is powered by the 8 volt supply inside the ECM. The sensor's output is a constant frequency signal with a duty cycle that varies with the pedal position. The sensor produces a minimum duty cycle of 10 percent at low idle and a maximum of 90 percent when the accelerator pedal is fully depressed. The ECM translates the duty cycle into an accelerator pedal position of 3 to 100 percent. Caterpillar Electronic Technician (ET) displays the value of the accelerator pedal position as "Accelerator Pedal Position".Automatic CalibrationThe ECM performs a new calibration of the accelerator pedal position sensor whenever the ECM is powered up.Initially, the ECM assumes that 22 percent duty cycle is equal to three percent of "Accelerator Pedal Position". As a result, some movement of the accelerator pedal may be required for the "Accelerator Pedal Position" to increase above three percent. The ECM assumes that 75 percent duty cycle is equal to 100 percent of "Accelerator Pedal Position". As a result, the "Accelerator Pedal Position" may reach 100 percent well before the accelerator pedal is fully depressed. This is normal operation.After some cycling of the accelerator pedal from the low idle position to the high idle position, the ECM automatically adjusts the "Accelerator Pedal Position" so that the entire available output from the sensor is used.Accelerator Pedal Position Sensor and PTO OperationIf the vehicle uses the ECM dedicated PTO functions, the output from the accelerator pedal position sensor is affected by several parameters. The "PTO Configuration" can be programmed to one of these three values:Remote Switches - The output from the accelerator pedal position sensor is ignored.Remote Throttle - The output from the accelerator pedal position sensor is ignored.Cab Switches - The output from the accelerator pedal position is ignored if the "PTO Cab Throttle RPM Limit" is programmed to "Low Idle".
Illustration 1 g00642016
Typical schematic for the cab's accelerator pedal position sensor
Note: The return wire may be connected to P1-3, P1-5, or P1-18.Background Information for the Remote Accelerator Position SensorA remote accelerator position sensor may be used for PTO purposes. The remote accelerator position sensor must be connected to terminal J1/P1-68 of the Engine Control Module (ECM). Before the ECM will respond to the remote accelerator position sensor, the ECM "PTO Configuration" must be programmed to "Remote Throttle", and the "PTO On/Off Switch" must be in the ON position.The remote accelerator position sensor must be powered from the vehicle battery (+12 VDC or +24 VDC). A version of the accelerator position sensor that is powered by the vehicle's battery must be used for the remote accelerator position sensor, and a accelerator pedal position sensor that is powered by +8 VDC from the ECM must be used in the cab.The ECM will not respond to the remote accelerator position sensor while a 630-2 (J1939) Calibration Memory : Erratic, Intermittent, or Incorrect code is active. Refer to Troubleshooting, "ECM Memory - Test" if the 630-2 (J1939) diagnostic code is active.The remote accelerator position sensor provides a throttle position signal to the ECM. The output of the remote accelerator position sensor is a constant frequency signal with a pulse width that varies with the position of the sensor. This output signal is referred to as either a duty cycle or a pulse width modulated signal (PWM).The output signal of the remote accelerator position sensor is expressed as a percentage between 3 and 100 percent. The accelerator position sensor will produce a duty cycle of 10 to 22 percent at low idle and 75 to 90 percent when the sensor is fully actuated. The percent of duty cycle is translated in the ECM into a throttle position of 3 to 100 percent.If the vehicle is using the ECM dedicated PTO functions, the accelerator position sensor will be ignored while the engine is in "PTO Mode" and the "PTO Configuration" is programmed to the "Remote Throttle" option.The ECM is in "PTO Mode" while the PTO on/off switch is ON. This can be checked through the status screen on Caterpillar Electronic Technician (ET).The ECM will not respond to the remote accelerator position sensor when both of the following conditions are met:
The PTO on/off circuit is switched from the OFF position to the ON position.
The ECM reads the remote accelerator position sensor above low idle.This prevents the engine from experiencing unexpected acceleration or sudden acceleration when the PTO on/off circuit is turned ON. The remote accelerator position sensor must return to low idle before the ECM will respond. The ECM must also see a transition from the OFF position to the ON position in the PTO on/off switch in order to allow the other PTO speed control functions to operate. If the engine is started with the PTO on/off switch in the ON position, the accelerator will respond. The response will occur only if the accelerator pedal is first returned to the low idle position. The other engine speed controls will not respond.
Illustration 2 g01275106
Typical schematic for remote accelerator pedal position sensor
Note: The return wire may be connected to P1-3, P1-5, or P1-18.
Illustration 3 g01182700
P1 terminals for the pulse width modulated sensors (PWM)
(3) Return
(4) + 8V
(5) Return
(18) Return
(66) Accelerator pedal position
(68) Remote accelerator position sensor Test Step 1. Inspect Electrical Connectors and Wiring
Thoroughly inspect ECM vehicle harness connector J1/P1, the firewall bulkhead connector and the accelerator pedal position sensor connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10