SEAL 7K9220 - Caterpillar

System Operation Description:Table 1 lists the diagnostic codes that are covered by this procedure.
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