0127280 JOHNSON KEY, #71

Table 1
Diagnostic Codes Table    
Description    Conditions which Generate this Code    System Response    
110-3 Engine Coolant Temperature Sensor : Voltage Above Normal    The Electronic Control Module (ECM) detects signal voltage that is above normal for eight seconds.
The ECM has been powered for at least two seconds.    The code is logged.
If equipped, the warning light will illuminate.
The ECM flags engine coolant temperature as invalid data and a default value of
90 °C (194 °F) is used.    
110-4 Engine Coolant Temperature Sensor : Voltage Below Normal    The ECM detects signal voltage that is below normal for eight seconds.
The ECM has been powered for two seconds.    
172-3 Intake Manifold Air Temperature Sensor : Voltage Above Normal     The ECM detects signal voltage that is above normal for eight seconds.
The ECM has been powered for at least two seconds.     The code is logged.
If equipped, the warning light will illuminate.
The ECM flags intake manifold air temperature as invalid data. The default value of
−10 °C (14.0°F) is used.    
172-4 Intake Manifold Air Temperature Sensor : Voltage Below Normal     The ECM detects signal voltage that is below normal for eight seconds.
The ECM has been powered for two seconds.    
174-3 Fuel Temperature Sensor : Voltage Above Normal     The ECM detects signal voltage that is below normal for eight seconds.
The ECM has been powered for two seconds.     The code is logged.
If equipped, the warning light will illuminate.
The ECM flags fuel temperature as invalid data and a default value is used.    
174-4 Fuel Temperature Sensor : Voltage Below Normal     The ECM detects signal voltage that is below normal for eight seconds.
The ECM has been powered for two seconds.     The code is logged.
If equipped, the warning light will illuminate.    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.The troubleshooting procedures for the diagnostic codes of each temperature sensor are identical. The temperature sensors are passive sensors.
Illustration 1 g01323624
Schematic for engine temperature sensors
Illustration 2 g01170313
Engine coolant temperature sensor and intake manifold air temperature sensor (1) Sensor signal (2) Sensor return
Illustration 3 g01325174
A typical view of the P2connector (harness side) pin locations. (37) Intake manifold air temperature sensor return (37) Coolant temperature sensor return (42) Intake manifold air temperature sensor signal (43) Coolant temperature sensor signal (41) Fuel temperature sensor signal (37) Fuel temperature sensor return
Illustration 4 g01345594
A typical view of the P2 connector (ECM side) pin locations.Test Step 1. Inspect Electrical Connectors And Wiring.
Turn the keyswitch to the OFF position.
Illustration 5 g01325579
Typical engine ECM (1) J2 ECM connector (2) J1 ECM connector
Thoroughly inspect the ECM engine harness connector and the suspect sensor connector. Refer to service Troubleshooting, "Electrical Connectors - Inspect".
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the temperature sensors.Refer to illustration 4.
Verify that the latch tab of the connector is correctly latched. Also verify that the latch tab of the connector has returned to the fully latching position.
Check the allen head screws for each ECM connector for the proper torque. Refer to service Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness for abrasions, for pinch points, and for corrosion.Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness is free of corrosion, of abrasion, and of pinch points.Results:
OK - The connectors and wiring appear to be 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.If applicable, use Caterpillar Electronic Technician (ET) to perform a wiggle test.STOPTest Step 2. Check for Active Diagnostic Codes
Connect the Cat 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 for the diagnostic codes to become active.
Look for a -3 diagnostic code or a -4 diagnostic code.Expected Result:No diagnostic codes are active.Results:
OK - No diagnostic codes are active. The problem appears to be resolved.Repair: The problem may have been intermittent. Carefully reinspect the connectors and wiring. Refer to service Troubleshooting, "Electrical Connectors - Inspect".If applicable, use Cat ET to perform a wiggle test .STOP
Not OK - A -4 diagnostic code is active at this time. Proceed to Test Step 3.
Not OK - A -3 diagnostic code is active at this time. Proceed to Test Step 4.Test Step 3. Disconnect the Suspect Sensor in Order to Create an Open Circuit
Turn the keyswitch to the OFF position.
Disconnect the suspect sensor from the engine harness.