0510827 JOHNSON TERMINAL

Table 1
Diagnostic Codes Table    
Code and 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, the engine ECM detects 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, the engine ECM detects a duty cycle that is greater than 95 percent for one second.     The throttle signal defaults to a zero percent duty cycle.    The throttle position sensor provides a throttle position signal to the engine ECM. The pedal mounted throttle position sensor is attached directly to the assembly. The pedal mounted throttle position sensor cannot be adjusted.The engine ECM receives a pulse width modulated signal from the throttle position sensor. The ECM converts the duty cycle of the signal into a usable throttle position. The duty cycle must be between 5 percent and 95 percent for a valid signal. The frequency of the signal must be a fixed frequency between 150 Hz and 1000 Hz. The ECM displays the throttle position as a percentage between 0 and 100 percent.
Illustration 1 g02581502
Typical schematicTest Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01234146
Location of ECM connectors
Thoroughly inspect the J1/P1 ECM connectors, the machine connectors, and the connectors for the throttle position sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01573106
P1 ECM connector (P1-4) +8 V digital supply (P1-5) Digital return (P1-10) Throttle signal
Illustration 4 g02581505
Machine Connector (Terminal 17) +8 V digital supply (Terminal 36) Digital return (Terminal 19) Throttle position
Illustration 5 g01159881
Terminal locations at the connector for the throttle position sensor (Terminal A) +8 V digital supply (Terminal B) Digital return (Terminal C) Throttle position
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the sensor connectors that are associated with the active diagnostic code.
Check the allen head screw for each of the ECM connectors and the machine connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for abrasions and for pinch points from the sensor back to the ECM.Expected Result:All connectors, pins, and sockets are inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem in the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled.Verify that the repair eliminates the problem.STOPTest Step 2. Inspect the Throttle Assembly
Inspect the throttle assembly for components that are loose, bent, missing, or worn.
Operate the throttle assembly through the full range of motion.Expected Result:The throttle assembly operates smoothly without excessive drag. The throttle assembly returns to the low idle position without assistance in less than one second.Results:
OK - The throttle assembly is operating correctly. Proceed to Test Step 3.
Not OK - The throttle assembly is not operating correctly.Repair: Repair the throttle assembly or replace the throttle assembly. The throttle assembly should return to the low idle position without assistance in less than one second.STOPTest Step 3. Check the Status for "Throttle Position"
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the keyswitch to the ON position.
Observe the status for "Throttle Position" on Cat ET while you operate the throttle.
Turn the keyswitch to the OFF position.Expected Result:The throttle position reads 0 percent when the throttle pedal is released. The throttle position increases to 100 percent when the throttle pedal is fully depressed.Results:
OK - The throttle position sensor is working properly.Repair: There may be an intermittent electrical problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting the problem.STOP
Not OK - The status is not correct on Cat ET. There may be a problem with the throttle position sensor. Proceed to Test Step 4.Test Step 4. Check the Supply Voltage at the Sensor
Disconnect the connector for the throttle position sensor.
Turn the keyswitch to the ON position.
Measure the voltage between terminals A and B on the harness side of the sensor connector.
Turn the keyswitch to the OFF position.Expected Result:The voltage is 8.0 0.4 VDC.Results:
OK - The voltage is 8.0 0.4 VDC. The voltage is correct. Proceed to Test Step 5.
Not OK - The voltage is not 8.0 0.4 VDC. Proceed to Test Step 8.Test Step 5. Check the Signal Frequency and the Duty Cycle at the Sensor
Remove the wire from terminal C (signal) on the harness side of the connector for the throttle position sensor.
Install a 7X-6370 Adapter Cable As (3-PIN BREAKOUT) at the connector. Connect the connectors for the sensor.
Turn the keyswitch to the ON position.
Use a multimeter to measure the signal frequency and the duty cycle. Measure between terminal B (digital return) and terminal C (signal) at the breakout while you operate the throttle pedal.
Turn the keyswitch to the OFF position.
Remove the breakout from the circuit. Restore the wiring to the original configuration.Expected Result:The frequency is between 150 and 1000 Hz. The duty cycle is between 5 percent and 95 percent.Results: