SWITCH AS-TRANSMISSION 4727835 - Caterpillar

System OperationThe sensor signal for the passive sensor is routed from the ECM to terminal 2 of the sensor connector. The sensor return for the passive sensors is routed from the ECM to terminal 1 of the sensor connector.
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Typical schematic
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P1 ECM connector (P1-3) Analog return (P1-14) Intake manifold air temperature sensor
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Location of ECM connectors
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Sensor connector (Terminal 1) Analog return (Terminal 2) Intake manifold air temperature sensorTest Step 1. Check for "Active" or "Logged" Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the main disconnect switch to the ON position.
Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Determine if a diagnostic code has occurred several times.Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a poor connection between a socket and a pin in a connector or of a poor connection between a wire and a terminal.
Determine if the problem is active and related to one of the following diagnostic codes:
-3
-4Expected Result:A diagnostic code is not active.Results:
OK - A diagnostic code is not active.Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - An active -3 diagnostic code is present. Proceed to Test Step 2.
Not OK - An active -4 diagnostic code is present. Proceed to Test Step 3.Test Step 2. Create a Short at the Sensor Connector
Turn the main disconnect switch to the OFF position.
Disconnect the suspect sensor.
Use a wire jumper in order to create a short between terminal 2 (signal) and terminal 1 (sensor return) at the sensor connector.
Turn the main disconnect switch to the ON position.
Access the "Active Diagnostic Code" screen on Cat ET. Check for an active -4 diagnostic code for the suspect sensor.Expected Result:A -4 diagnostic code is now active for the suspect sensor(s).Results:
OK - A -3 diagnostic code was active before creating the short at the sensor connector. A -4 diagnostic code became active after creating the short at the sensor connector. The wiring between the ECM and the sensor connector is OK.Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.STOP
Not OK - A -3 diagnostic code is still active for the suspect sensor(s). There is an open circuit between the sensor connector and the ECM. Leave the sensor disconnected. Proceed to Test Step 4.Test Step 3. Create an Open at the Suspect Sensor Connector
Turn the main disconnect switch to the OFF position.
Disconnect the sensor connector of the suspect sensor(s) with the active -4 diagnostic code.
Turn the main disconnect switch to the ON position. Wait at least 30 seconds for activation of the