MID 039 - Machine Control Module
CID 0838 - Left Front Strut Pressure Sensor
FMI 21 - Data Drifted Low
Illustration 1 | g06042376 |
Mini schematic of the left front strut pressure sensor circuit |
This diagnostic code is activated if the strut pressure falls below (
Test Step 1. CONFIRM NO OTHER STRUT DIAGNOSTICS ARE ACTIVE
- Using Cat ET confirm that no other strut diagnostics are active.
Expected Result:
No other strut diagnostics are active
Results:
- OK - No other strut diagnostics are active. Proceed to Test Step 1.
- NOT OK - There are other diagnostics active.
Repair: Troubleshoot all other codes before proceeding
STOP
Test Step 2. CONFIRM CORRECT STRUT PRESSURES AND STRUT CHARGE BY PERFORMING THE STRUT CHARGING PROCEDURE
Reference: Refer to Special Instruction, SEHS9411, "Servicing the Suspension Cylinders for Large Off-Highway Trucks" for the Strut Charging Procedure.
Note: You will need to drive the truck for 30 seconds after performing the Strut Charging Procedure, to confirm that the diagnostic code is no longer active.
Expected Result:
The diagnostic code is no longer active.
Results:
- OK - Strut pressures and strut charge are OK. The diagnostic code is no longer active.
STOP
- NOT OK - The strut pressures and strut charge are NOT OK after performing the Strut Charging Procedure. Proceed to Test Step 1.
Test Step 3. CHECK THE SENSOR SUPPLY VOLTAGE
- Locate the suspect sensor.
- Identify the sensor wires and connector contacts.
Note: Do not disconnect any harness connectors.
- Turn on the keyswitch.
Note: The truck can be empty or the truck can be loaded.
- At the sensor connector, identify the +V and ground circuits.
- Insert 7X-1710 Multimeter Probe leads beside the +V and ground circuit wires in the back of the connector for the sensor .
- Measure the voltage.
Expected Result:
The voltage is between 22.0 DCV and 29.5 DCV.
Results:
- OK - The voltage is between 22.0 DCV and 29.5 DCV. Proceed to Test Step 1.
- NOT OK - The voltage is not between 22.0 DCV and 29.5 DCV.
Repair: Trace the +V and ground circuits in the harness.
Perform one of the following:
- Repair or replace the harness if the harness has failed
- Replace the sensor if the harness has not failed
STOP
Test Step 4. CHECK THE SENSOR SIGNAL VOLTAGE
- At the sensor connector, identify the signal and ground circuits.
- Insert 7X-1710 Multimeter Probe leads beside the signal and ground circuit wires in the back of the connector for the sensor.
- Measure the voltage.
Expected Result:
The voltage is between 1.0 DCV and 9.0 DCV.
Results:
- OK - The voltage is between 1.0 DCV and 9.0 DCV. Proceed to Test Step 1.
- NOT OK - The voltage is greater than 9.0 DCV Proceed to Test Step 1.
- NOT OK - The voltage is less than 1.0 DCV. Proceed to Test Step 1.
Test Step 5. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO +BATTERY
- Disconnect the sensor from the harness.
- At the harness connector for the sensor, measure the voltage between the signal contact and the ground contact.
Expected Result:
The voltage is less than 9.0 DCV.
Results:
- NOT OK - The voltage is above 9.0 DCV. The signal circuit is shorted to the +battery or the Input/Output Module has failed.
Repair: Trace the signal and ground circuits in the harness. Repair or replace the harness. If the harness is correct, the Input/Output Module may have failed. Contact the Technical Communicator at your Cat® Dealer.
STOP
- OK - The voltage is between 1.0 and 9.0 DCV. The voltage is correct, the sensor has failed.
Repair: Replace the sensor.
STOP
Test Step 6. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND
- Disconnect the sensor from the harness.
- At the harness connector for the sensor, measure the voltage between the signal contact and the ground contact.
Expected Result:
The voltage is between 1.0 and 9.0 DCV.
Results:
- OK - The voltage is between 1.0 and 9.0 DCV. The voltage is correct, the sensor has failed.
Repair: Replace the sensor.
STOP
- NOT OK - The voltage is less than 1.0 DCV.
Repair: Possible causes:
- Incorrect Input/Output Module software installed
- Signal circuit shorted to ground in the harness
- Input/Output Module has failed
- Check that the correct Input/Output Module software is installed.
Install the correct Input/Output Module software.
- Trace the signal circuit and the ground circuit in the harness.
Repair or replace the harness.
- If the harness is correct, the Input/Output Module may have failed.
Contact the Technical Communicator (TC) at your Cat® Dealer.
STOP
Test Step 7. CHECK THE SENSOR SIGNAL FREQUENCY
- Remove the sensor from the suspension cylinder.
Note: Do NOT disconnect the harness connector.
- At the harness connector for the sensor, identify the signal and ground circuits.
Note: Do NOT disconnect or reconnect the harness connector.
- Insert 7X-1710 Multimeter Probe leads beside the signal and ground circuit wires in the back of the connector for the sensor.
- Measure the frequency between the signal and the ground contacts.
Expected Result:
The frequency is between 186 Hz and 214 Hz when ambient temperature is between
Results:
- OK - The frequency is correct. If the problem of incorrect payload measurement persists, proceed to Test Step 1.
- NOT OK - The frequency is not correct. The sensor has failed.
Repair: Replace the sensor.
STOP
Test Step 8. MOVE THE SENSOR
- Substitute the suspect sensor with a properly functioning sensor.
For example, substitute the suspect left front suspension cylinder pressure sensor with a good right front suspension cylinder pressure sensor.
- Verify that the problem followed the suspect sensor to the other suspension cylinder.
Verify that the problem followed the suspect sensor:
- Ride in the truck during the loading operation
- Observe the performance of the four suspension cylinder pressure sensors by using Cat ET or by activating a data logger
- Compare the signal outputs of the four sensors
- Verify that the suspect sensor does not respond to the loading of the truck in the same manner as the other sensors
Expected Result:
The problem followed the sensor to the other suspension cylinder.
Results:
- OK - The problem followed the sensor to the other suspension cylinder. The sensor has failed.
Repair: Replace the sensor.
STOP
- NOT OK - The problem did not follow the sensor to the other suspension cylinder. The suspension cylinder is causing the failure.
Repair: Contact the Technical Communicator (TC) at your Cat® Dealer.
STOP