COVER 2175164 - Caterpillar

This procedure covers the following diagnostic codes:
91-08 Throttle Position signal abnormalThe throttle switch provides the operator with the ability to select the desired engine speed. The throttle switch is a rotary switch with ten positions. The throttle switch is connected to the four switch inputs of the engine and hydraulic pump controller. A throttle command is sent to the engine's Electronic Control Module (ECM) from the engine and hydraulic pump controller. The throttle command is referred to as a duty cycle or as a PWM signal. The throttle command is valid when the following conditions exist:
The duty cycle is between 5 percent and 95 percent.
The PWM signal is 1.228 kHz 150 Hz.When a diagnostic code is generated, the ECM ignores the throttle command and the desired engine speed is set to the last valid speed that was recognized by the ECM. When a problem is detected with the throttle signal, the throttle backup switch is enabled. The operator can use the throttle backup switch to set the desired engine speed. If the throttle backup switch is held in the ACCEL position, the desired engine speed will increase 200 rpm per second. If the throttle backup switch is held in the DECEL position, the engine speed will decrease 200 rpm per second.
Illustration 1 g01253310
Schematic
Table 1 shows continuity between the contacts of the throttle position switch in each position.
Table 1
Throttle Position Switch
Position Contacts
1 COM, S1
2 COM, S1, S2
3 COM, S2
4 COM, S2, S3
5 COM, S1, S2, S3
6 COM, S1, S3
7 COM, S3
8 COM, S3, S4
9 COM, S1, S3, S4
10 COM, S1, S2, S3, S4
Illustration 2 g01120703
P1 ECM connector
(P1-5) Digital return
(P1-22) Throttle backup switch
(P1-23) Throttle backup switch
(P1-66) Throttle command Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that is associated with the active diagnostic code.
Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and wiring for abrasions and for pinch points from the sensors back to the ECM. 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 harness and wiring are 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 completely coupled.Verify that the repair eliminates the problem.STOPTest Step 2. Check for Active Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the keyswitch to the ON position.
Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order