VALVE 0003640 - Caterpillar

The throttle switch and the decelerator pedal provide the operator with the ability to select the desired engine speed. The throttle switch is a two-position switch. When the engine is at low idle, pressing the throttle switch to the high idle position will cause the engine speed to increase to high idle. When the engine is above low idle, pressing the throttle switch in the low idle position will cause the engine speed to return to low idle.The decelerator pedal can be used to decrease the engine speed once the engine is at high idle. Holding the throttle switch in the high idle position will cause the ECM to control the engine speed at the current speed.The throttle switch is connected to four throttle inputs at the Electronic Control Module (ECM). Each position of the throttle switch generates a specific on/off pattern on the throttle inputs. A diagnostic code is generated if the pattern does not correspond with any of the valid patterns.Once a diagnostic code is generated, the ECM ignores the throttle input signals and desired engine speed is set to the last valid pattern that was recognized by the ECM.Voltage at the throttle inputs to the ECM is 7.5 0.5 VDC when the throttle inputs are open. The voltage is less than 0.5 VDC when the throttle inputs are closed.
Illustration 1 g02065558
Schematic
Illustration 2 g01013030
P1 ECM connector
Test Step 1. Inspect Electrical Connectors and Wiring
Place the engine control in the OFF/RESET mode.
Thoroughly inspect the J1/P1 ECM connector, J61/P61 machine connector, and the J702/P702 throttle switch connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and wiring for corrosion, for abrasion, and for pinch points from the throttle switch to the ECM. Expected Result:All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 2. Check the Status of the Throttle Switch
Connect the Caterpillar Electronic Technician (ET) to the service tool connector.
Place the engine control in the ON mode.
Observe the status of the throttle switch and the throttle inputs on Cat ET while you operate the throttle switch in each position.
Table 1
Status for the Throttle Switch
Released Low Idle High Idle
Input 1 Off On Off
Input 2 On On Off
Input 3 Off Off On
Input 4 On Off On Expected Result:The status of the throttle switch and the status of the inputs changes according to Table 1.Results:
OK - The throttle switch is functioning properly at this time.Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.STOP
Not OK - Note the suspect input. Proceed to Test Step 3.Test Step 3. Jumper the Switch Input at the Throttle Switch Connector
Disconnect the J702/P702 throttle