0391658 JOHNSON THRUST WASHER PKG.

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 ECM has been powered for three seconds.     The code will be active.
The throttle signal defaults to a zero percent duty cycle.    
The throttle signal to the ECM is a pulse width modulated signal (PWM). The ECM displays the throttle position as a percentage between 0 and 100 percent. The remote PWM signal is provided by the customer. The duty cycle of the PWM signal must be between 5 percent and 95 percent for a valid signal. The frequency of the PWM signal must be a frequency between 150 Hz and 1000 Hz.A potentiometer that is mounted in the user interface panel can be used to send a signal to the customer's speed control in order to allow local speed control of the engine. The potentiometer is only available on the ECP or retrofit option of the user interface panel.
Illustration 1 g01277305
Typical schematic
Illustration 2 g01277308
P1 ECM connector (P1-10) Remote PWM
Illustration 3 g01277310
Connector for the user interface panel (Terminal 15) Remote PWM
Illustration 4 g01234146
Location of ECM connectorsTest Step 1. Check the Throttle Position with Caterpillar Electronic Technician (ET)
Connect Cat ET to the service tool connector. Start Cat ET.
Turn the local/remote switch on the control panel to the LOCAL position.
Observe the throttle position on Cat ET.
Adjust the throttle from low idle to high idle.Expected Result:The throttle position reads 0 percent when the throttle is at low idle. The throttle position increases to 100 percent when the throttle is at high idle.Results:
OK - The throttle position reads 0 percent when the throttle is at low idle. The throttle position increases to 100 percent when the throttle is at high idle. The throttle signal is OK.Repair: There may be an intermittent problem. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".STOP
Not OK - PWM - The throttle position is not 0 percent when the throttle is at low idle. The throttle position is not 100 percent when the throttle is at high idle. The ECM is not receiving a correct throttle signal. There may be a problem in the harness. Proceed to Test Step 2.Test Step 2. Check the