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| Illustration 1 | g02222833 |
Front Differential and Right Front Axle Speed Sensor | |
The MID 087, CID 3535 diagnostic code is associated with the Right Front Axle Speed Sensor that provides a square wave frequency input signal to the Chassis ECM.
The FMI 02 means that the Chassis ECM has detected an incorrect condition in the speed sensor input signal circuit.
This speed sensor reacts differently than the typical speed sensor. This sensor can determine that a pulse signal is present between the sensor and the Chassis ECM.
The speed sensor does not measure wheel speed directly. The sensor determines wheel speed from the measured differential case speed and side gear speed (same speed as axle shaft). The ECM detects the frequency of the signal change and uses the frequency to determine the speed of the wheel.
The FMI 2 diagnostic fault code activates for the following possible causes:
- The front differential speed sensor and right axle speed sensor are interchanged in the system.
- The sensor is internally faulted.
The inputs that impact the FMI 2 diagnostic codes are listed below:
- Input from the speed sensor
- Input from the transmission gear
- Input from the inertial measurement sensor
System Response:
- ATC is not available
- The ATC will automatically engage the interaxle lock clutch when throttle and retarding are available
- ATC lamp on the main cluster display will flash when the fault is active and a warning message will pop up on the CMPD
Note: The CID 3535 FMI 02 diagnostic code may be an intermittent condition.
Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.
Test Step 1. VERIFY THE HARNESS CONNECTIONS TO THE SENSOR
The key start switch and the battery disconnect switch must be in the OFF position.
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| Illustration 2 | g02216834 |
Speed Sensor Access Cover | |
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| Illustration 3 | g02216836 |
(1) Axle Speed Sensor (2) Differential Speed Sensor | |
- Open the access cover on the differential carrier to access the front differential speed sensor and the right front axle speed sensor.
Note: Facing the pinion yoke side of the differential carrier the two speed sensors are located on the right-hand side of the carrier. The upper sensor is the axle speed sensor and the lower sensor is the differential speed sensor.
- Visually inspect the wiring harness for the differential speed sensor to ensure that the correct harness connector is going to the correct speed sensor.
Note: Verify the correct wires with the schematic provided.
Expected Result:
The harness connections are in the correct locations.
Results:
- YES - The harness connections are in the correct locations. Proceed to Test Step 2.
- NO - The harness connections are not in the correct location.
Repair: Remove and connect the harness connector to the correct sensor. Turn the disconnect switch and the key start switch to the ON position. Operate the machine. Check the status of the CID 3535 FMI 02 code. Note: The machine must move (Forward or Reverse gear and Forward or Reverse speed) to detect or clear the CID 3535 FMI 02 code.
STOP
Test Step 2. CHECK IF THE INERTIAL SENSOR HAS ACTIVE DIAGNOSTIC CODE
- Use Cat ET to determine if any diagnostic codes are active on the inertial measurement sensor.
Expected Result:
The inertial sensor is faulted.
Results:
- OK - Resolve the inertial sensor fault by following the troubleshooting procedure for the Inertial Measurement Sensor. Confirm the CID 3535 FMI 02 is no longer active. The machine must move (forward or reverse gear and forward or reverse speed) to detect or to clear the CID 3535 FMI 02 code.STOP
- NOT OK - The CID 3535 FMI 02 is active. The diagnostic code has not been corrected.
Repair: Contact the Technical Communicator for your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Troubleshooting, "Electronic Control Module (ECM) - Replace".If the cause of the problem is not found, contact the Technical Communicator for your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Troubleshooting, "Electronic Control Module (ECM) - Replace"
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