How to Solve CAT C9 Engine 8 Volt Supply Voltage High Problem

This instruction show you guide on how to solve Caterpillar C9 engine 8 volt supply voltage high fault.

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The Engine Control Module (ECM) detects the following conditions:

-The 8 volt supply is more than 8.5 VDC for more than one second.

-The ECM has been powered for more than three seconds.

The accelerator pedal position sensor is used to provide a throttle position signal to the Engine Control Module (ECM).Sensor output is a constant frequency signal with a pulse width that varies with the pedal position. This output signal is referred to as either a duty cycle or a pulse width modulated signal (PWM) and this output signal is expressed as a percentage between 3 and 100 percent.

The accelerator pedal position sensor is attached directly to the accelerator pedal assembly. The accelerator pedal position sensor requires no adjustment.

The accelerator pedal position sensor will produce a duty cycle of 10 to 22 percent at low idle and 75 to 90 percent when the accelerator pedal is fully depressed.The percent of duty cycle is translated in the ECM into an accelerator pedal position of 3 to 100 percent.

The accelerator pedal position sensor is powered by the ECM supply voltage(DC from connector P1-4 to terminal “A”of the accelerator pedal position sensor connector The accelerator pedal position sensor can be replaced separately from the pedal assembly. An incorrectly calibrated pedal assembly can not be adjusted.The entire pedal assembly must be replaced.

If the vehicle is using the ECM dedicated PTO functions,the accelerator pedal position sensor will be ignored while the engine is in PTO mode and the “PTO Configuration” is programmed to one of the following parameters:

Probable Causes:

1) ECM Connection

2) Accelerator pedal position sensor or harness

3) Wiring between accelerator pedal position sensor and ECM

4) ECM Failure

5) Accelerator pedal assembly

More repair case for Caterpillar machine,please refer to:Caterpillar Machine Repair

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