BLOCK-COUPLING 6T8526 - Caterpillar

System Operation Description:Use this procedure to troubleshoot any suspect problems with the following sensors:
Coolant temperature sensor
Engine oil temperature sensor
Fuel temperature sensor
Intake manifold air temperature sensorThis procedure covers the following diagnostic codes:
110-03 Engine Coolant Temperature open/short to +batt
110-04 Engine Coolant Temperature short to ground
172-03 Intake Manifold Air Temp open/short to +batt
172-04 Intake Manifold Air Temp short to ground
174-03 Fuel Temperature open/short to +batt
174-04 Fuel Temperature short to ground
175-03 Engine Oil Temperature open/short to +batt
175-04 Engine Oil Temperature short to groundThe troubleshooting procedures for the diagnostic codes for each of the temperature sensors are identical. The temperature sensors are passive sensors that have two terminals. The temperature sensors do not require supply voltage from the Electronic Control Module (ECM).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 a problem 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 (03) 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 OK. If the sensor is disconnected at the sensor connector, the absence of pull-up voltage at the sensor connector indicates a problem in the signal wire. 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 g01241464
Schematic for the engine temperature sensors
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove electrical power from the ECM.
Illustration 2 g01241499
Locations of the engine temperature sensors (typical left side engine view)
(1) Intake manifold air temperature sensor
(2) Fuel temperature sensor
(3) J2/P2 ECM connectors
(4) J1 ECM connector
Illustration 3 g01241515
Locations of the engine temperature sensors (typical right side engine view)
(5) Engine coolant temperature sensor
(6) Engine oil temperature sensor
Thoroughly inspect the connectors for sensors (1), (2), (5), and (6). Also, thoroughly inspect ECM connectors (3) and (4). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 4 g01241522
Terminal locations at the P2 ECM connector for the engine temperature sensors
(P2-13) Engine coolant temperature
(P2-30) Sensor return
(P2-56) Intake manifold air temperature
(P2-62) Fuel temperature
Illustration 5 g01241529
Terminal locations at the P1 ECM connector for the engine temperature sensors
(P1-26) Engine oil temperature
Illustration 6 g01241538
Connector for the temperature sensors
(1) Sensor signal
(2) Sensor return
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the temperature sensors.
Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for correct torque values.
Check the harness and wiring for abrasions and for pinch points from each sensor to the ECM. Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The connectors and wiring appear to be OK.