Case IH 12608 – ABS Module / TECU: Rear left wheel speed sensor - open circuit or shorted to battery.

The control module is not receiving a valid signal from the rear left wheel speed sensor because the electrical circuit is either broken (open) or a wire is shorting directly to a power source (battery voltage).

• Puma 165
• Puma 185
• Puma 200
• Puma 215
• Puma 230
• Optum
• Magnum

1. 1

   Inspect the wiring harness leading to the rear left wheel speed sensor for visible damage, cuts, or chafing against the chassis or axle.

2. 2

   Disconnect the sensor and inspect the connector pins for corrosion, moisture ingress, or bent pins.

3. 3

   Using a multimeter, check the sensor signal and ground wires for continuity back to the ABS module/TECU to rule out an open circuit in the main harness.

4. 4

   With the key ON (engine off), probe the sensor signal wire to ensure it is not receiving unintended battery voltage (which would confirm the shorted to battery condition).

5. 5

   Measure the internal resistance of the wheel speed sensor itself to see if it has failed internally (open circuit).

1. 1

   Safely park the tractor on level ground, engage the parking brake, and turn off the engine. Disconnect the negative battery terminal to prevent electrical spikes.

   Safely park the tractor on level ground, engage the parking brake, and turn off the engine. Disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Locate the rear left wheel speed sensor on the rear axle/hub assembly.

   Locate the rear left wheel speed sensor on the rear axle/hub assembly.

3. 3

   Disconnect the electrical connector from the sensor harness.

   Disconnect the electrical connector from the sensor harness.

4. 4

   Remove the retaining bolt securing the sensor to the axle housing.

   Remove the retaining bolt securing the sensor to the axle housing.

5. 5

   Carefully pull the sensor out of its mounting bore. Clean the mounting surface and inspect the internal tone ring (if visible) to ensure no debris or metal shavings will interfere with the new sensor.

   Carefully pull the sensor out of its mounting bore. Clean the mounting surface and inspect the internal tone ring (if visible) to ensure no debris or metal shavings will interfere with the new sensor.

6. 6

   Install the new OEM wheel speed sensor and tighten the mounting bolt to the manufacturer's specified torque.

   Install the new OEM wheel speed sensor and tighten the mounting bolt to the manufacturer's specified torque.

7. 7

   Reconnect the electrical connector, ensuring it clicks securely into place. Secure the wire harness with cable ties (OEM part 82013031 or equivalent) to keep it away from moving parts.

   Reconnect the electrical connector, ensuring it clicks securely into place. Secure the wire harness with cable ties (OEM part 82013031 or equivalent) to keep it away from moving parts.

8. 8

   Reconnect the battery, turn the ignition on, and use a diagnostic tool to clear the fault codes. Test drive the tractor to verify the ABS system functions correctly and code 12608 does not return.

   Reconnect the battery, turn the ignition on, and use a diagnostic tool to clear the fault codes. Test drive the tractor to verify the ABS system functions correctly and code 12608 does not return.