SEAL AS 9W4866 - Caterpillar

System Operation Description:Use this procedure under the following circumstances:
Throttle switch inputs cannot be switched to ground.
Verification of the throttle switch is required.Also, use this procedure if another procedure has directed you here.The throttle switch provides the operator with the ability to select the desired engine speed. Engine speed will decrease with increasing load. The throttle switch is a rotary switch with ten positions.The throttle switch is connected to the four throttle inputs of the Electronic Control Module (ECM). Each position generates a specific on/off pattern on the throttle inputs. A diagnostic code is generated if a pattern that does not correspond with any of the switch positions is detected.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. Desired engine speed is set to low idle while the engine is not running.Voltage at the throttle inputs to the ECM should be 11.5 0.5 Volts DC when the throttle inputs are open. The voltage should be less than 0.5 Volts DC when the throttle inputs are closed.
Illustration 1 g01625557
Schematic diagram for the throttle switches (31 pin MIC)
Illustration 2 g01625558
Schematic diagram for the throttle switches (70 pin MIC)
Illustration 3 g01625559
Pin locations on the ECM connector
(11) Throttle Switch No.3
(19) Throttle Switch No.4
(20) Throttle Switch No.2
(28) Throttle Switch No.1
(37) Switch Return
Illustration 4 g01625560
Pin locations on the 31 pin MIC
(21) Throttle Switch No.1
(22) Throttle Switch No.4
(24) Throttle Switch No.3
(25) Throttle Switch No.2
(28) Switch Return
Illustration 5 g01332051
Pin locations on the 70 pin MIC
(11) Throttle Switch No.3
(19) Throttle Switch No.4
(20) Throttle Switch No.2
(28) Throttle Switch No.1
(37) Switch Return
Illustration 6 g01332048Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
Thoroughly inspect ECM connector J1/P1, machine interface connector J20/P20, and the battery connections. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and wiring for corrosion, abrasion, and pinch points from the throttle switch to the ECM. Expected Result:All connectors, pins, and sockets should be completely inserted and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the fault.STOPTest Step 2. Check "Throttle Switch Position" on the Electronic Service Tool
Turn the keyswitch to the OFF position.
Connect the electronic service tool to the diagnostic connector.
Turn the keyswitch to the ON position.
Observe the