NUT 4B2041 - Caterpillar

System Operation Description:Use this procedure under the following conditions:This procedure covers diagnostic codes that are associated with the following sensors:
Coolant temperature sensor
Intake manifold air temperature sensorUse this procedure to troubleshoot the system when one of the following diagnostic codes is active, logged or when a diagnostic code can easily be activated.
110-3 Engine Coolant Temperature Sensor voltage above normal
110-4 Engine Coolant Temperature Sensor voltage below normal
172-3 Intake Manifold Air Temperature Sensor voltage above normal
172-4 Intake Manifold Air Temperature Sensor voltage below normalThe following background information is related to this procedure:The troubleshooting procedures for the diagnostic codes of each temperature sensor are identical. The temperature sensors have two terminals. Pin P2:37 is the common connection for the engine temperature sensors. The common line is connected to each sensor connector terminal 2. Terminal 1 is the sensor output. The signal voltage from terminal 1 of each sensor is supplied to the appropriate terminal in the P2/J2 connector.Pull-up VoltageThe ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage in order to detect an open in the signal circuit. When the ECM detects the presence of a voltage that is above a threshold on the signal circuit, the ECM will generate an open circuit diagnostic code (3) for the sensor.If the sensor is disconnected at the sensor connector, the presence of pull-up voltage at the sensor connector indicates that the wires from the sensor connector to the ECM are not open or shorted to ground. If the sensor is disconnected at the sensor connector, the absence of pull-up voltage at the sensor connector indicates an open in the signal wire or a short to ground. If the sensor is disconnected at the sensor connector and the voltage at the sensor connector is different from pull-up voltage, the signal wire is shorted to another wire in the harness.
Illustration 1 g01761878
Schematic for engine temperature sensors
Illustration 2 g01459099
Pin locations for the temperature sensors on the P2 connector (37) Intake Manifold Air Temperature Sensor and Coolant Temperature Sensor Return (42) Intake Manifold Air Temperature Sensor Signal (43) Coolant Temperature Sensor Signal
Illustration 3 g01170313
Engine coolant temperature sensor and intake manifold air temperature sensor (1) Signal (2) ReturnTest Step 1. Verify All Active Diagnostic Codes
Connect the electronic service tool to the diagnostic connector.
Turn the keyswitch to the ON position.Note: Wait at least 30 seconds for activation of the diagnostic codes.
Use the electronic service tool in order to verify if any of the following diagnostic codes are active or recently logged:
110-3 Engine Coolant Temperature Sensor voltage above normal
110-4 Engine Coolant Temperature Sensor voltage below normal
172-3 Intake Manifold Air Temperature Sensor voltage above normal
172-4 Intake Manifold Air Temperature Sensor voltage below normalExpected Result:One or more of the preceding diagnostic codes are active or recently logged.Results:
Yes - Proceed to Test Step 2.
No - The fault is intermittent. Proceed to Test Step 8.Test Step 2. Inspect Electrical Connectors And Wiring
Thoroughly inspect ECM engine harness connector P2 and the suspect sensor connector. Refer to Troubleshooting, "Electrical