MID 87 - Chassis ECM
CID 75 - Steering Oil Temperature Sensor
FMI 3 - Voltage Above Normal
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| Illustration 1 | g06361681 |
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"Steering Oil Temperature" sensor circuit | |
This diagnostic code indicates that the "Chassis ECM" detects the steering oil temperature sensor voltage is above normal.
The following can cause this code:
- Failed sensor
- Open sensor supply circuit
- Open sensor ground circuit
- Signal circuit shorted to the +battery
- Open signal circuit
- Disconnected sensor
- ECM failure
System Response:
The "Steering Oil Temperature" indication is one of the following:
- Continuously at maximum temperature
- Intermittently at maximum temperature
Test Step 1. CHECK FOR POWER AT THE SENSOR
Do not disconnect the sensor from the harness.
- Turn on the disconnect switch and the key switch.
- At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the voltage supply wire (contact A).
- Measure the voltage from contact A to frame ground.
Expected Result:
The voltage is 8 ± 0.5 VDC.
Results:
- OK - The voltage is 8 ± 0.5 VDC. Proceed to Test Step 2.
- NOT OK - The voltage is not 8 ± 0.5 VDC. Proceed to Test Step 5.
Test Step 2. CHECK FOR SENSOR GROUND
- The harness remains connected to the sensor.
- Turn off the key switch and the disconnect switch.
- Remove the 7X-1710 Multimeter Probe from the voltage supply wire (contact A).
- At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the ground wire (contact B).
- Measure the resistance from contact B to frame ground.
Expected Result:
The resistance is less than 5 ohms.
Results:
- OK - The resistance is less than 5 ohms. Proceed to Test Step 3.
- NOT OK - The resistance is more than 5 ohms. Proceed to Test Step 5.
Test Step 3. CHECK THE SENSOR SIGNAL CIRCUIT
The harness remains connected to the sensor.
- At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the signal wire (contact C).
- At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the ground wire (contact B).
- Turn on the disconnect switch and the key switch.
- Measure the sensor signal.
Expected Result:
The sensor signal is valid.
Results:
- OK - The sensor signal is valid. Proceed to Test Step 4.
- NOT OK - The sensor signal is not valid. The sensor has failed.
Repair: Replace the sensor.
STOP
Test Step 4. CHECK THE SIGNAL CIRCUIT AT THE ECM
- Turn off the key switch and the disconnect switch.
- Insert the multimeter probes into the back of the ECM connector along J2-24 (wire A451-WH(White)) and J1-45 (wire C242-BK(Black)).
- Turn on the disconnect switch and the key switch.
- Monitor the sensor signal with a digital multimeter.
- Without disconnecting the sensor or hardware associated with the sensor from the machine, take the sensor through the full operating range.
Expected Result:
The sensor responds in the manner described at the beginning of this procedure.
Results:
- OK - The sensor responds in the manner described at the beginning of this procedure.
Repair: Exit this procedure and perform this procedure again. Contact your technical communicator. If the ECM requires replacement, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NOT OK - The sensor does not respond in the manner described at the beginning of this procedure. Proceed to Test Step 5.
Test Step 5. CHECK CONNECTIONS
- Inspect the harness.
Clean the harness connector contacts.
Inspect the harness connector contacts for corrosion or damage.
Inspect the wire insulation for damage caused by heat, corrosion, or chafing.
- Perform a
45 N (10 lb) pull test on each circuit wire. - Reconnect all harness connectors.
Verify that the connectors are fully seated and the clips are fastened.
- Check for intermittent problems. Using Cat® Electronic Technician (Cat® ET), perform a wiggle test on the harness.
- Turn on the disconnect switch and the key switch.
- Operate the machine.
- Check CID 75 FMI 3 status.
Expected Result:
CID 75 FMI 3 is not active.
Results:
- OK - CID 75 FMI 3 is not active.
Repair: The initial diagnostic code was probably caused by a poor connection at one of the connectors that was checked.
Resume normal operation.
STOP
- NOT OK - CID 75 FMI 3 is active. Proceed to Test Step 6.
Test Step 6. CHECK FOR A SHORTED HARNESS
The sensor and ECM remain disconnected from the harness.
The disconnect switch and the key switch remain in the off position.
- Perform the following:
- Measure the resistance between the signal contact C (wire A451-WH(White)) of the harness connector for the sensor and contact A (wire T800-OR(Orange)) of the 8 V sensor supply.
- Measure the resistance between the connector contact J2-24 (wire A451-WH(White)) of the ECM and contact C (wire A451-WH(White)) of the harness connector for the sensor.
Expected Result:
The resistance is greater than 5000 ohms.
Results:
- OK - The resistance is greater than 5000 ohms. Proceed to Test Step 7.
- NOT OK - The resistance is less than 5000 ohms. There is a short between the +battery or the 8 V sensor supply circuits and the signal circuit in the harness.
Repair: Repair or replace the harness.
STOP
Test Step 7. CHECK FOR AN OPEN HARNESS
The sensor and ECM remain disconnected from the harness.
The disconnect switch and the key switch remain in the off position.
- Measure the resistance of the signal circuit from the connector contact J2-24 (wire A451-WH(White)) for the ECM to the connector contact C (wire A451-WH(White)) for the sensor.
Expected Result:
The resistance is less than 5.0 ohms.
Results:
- OK - The resistance is less than 5.0 ohms. The ECM may have failed.
Repair: Exit this procedure and perform this procedure again. Contact the technical communicator at your Caterpillar dealer. If the ECM requires replacement, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NOT OK - The resistance is greater than 5.0 ohms. The harness is open.
Repair: Repair or replace the harness.
STOP