IDLER GP-FRONT 4962921 - Caterpillar

Table 1
Diagnostic Codes Table    
Description     Conditions which Generate this Code     System Response    
91-8 Throttle Position Sensor abnormal frequency, pulse width, or period     The Engine Electronic Control Module (ECM) detects a sensor frequency that is less than 150 Hz or a sensor frequency that is greater than 1000 Hz for two seconds.
OR
The engine ECM detects a duty cycle that is less than 5 percent or a duty cycle that is greater than 95 percent for one second.     The code will be active.
The throttle signal defaults to a zero percent duty cycle.    The direct fuel control mode enables the engine to be controlled by an external governor. You must install the components of the signal converter for the direct fuel control in order to operate in direct fuel control mode. The configuration parameter must be programmed to "Installed" in order for the ECM to respond properly to the external governor.The input to the signal converter is a DC current signal that is in the range of 0 to 200 mA. The signal to the converter is generated from an external governor. The output signal to the ECM from the signal converter is a Pulse Width Modulated signal (PWM). The PWM signal to the ECM is valid if the signal has a duty cycle in the range of 5 to 95 percent and the frequency of the signal is between 150 Hz and 1000 Hz. The ECM will convert the PWM signal into a throttle position of 0 to 100 percent. The throttle position on Caterpillar Electronic Technician (ET) will not match the duty cycle of the PWM signal. If an invalid signal is received, the engine will automatically be set to a minimum fuel setting and the engine will shut down.
Illustration 1 g01344589
"MMSII" panel
Illustration 2 g01344375
"Retrofit or ECP" panel
Illustration 3 g01277308
P1 ECM connector (P1-10) Remote PWM
Illustration 4 g01277310
Connector for the user interface panel (Terminal 15) Remote PWMTest Step 1. Inspect Electrical Connectors and Wiring
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The connectors and wiring are OK. Proceed to Test Step 2.
Not OK - The connectors and/or wiring are not OK.Repair: Repair the connectors or wiring and/or replace the connectors or wiring.STOPTest Step 2. Check the Throttle Position
Connect Cat ET to the service tool connector. Start Cat ET.
Observe the throttle position reading on Cat ET.
Vary the current to the signal converter from the lowest setting