Wheel Speed Sensor

Replacing a Wheel Speed Sensor on a Lotus Exige 390 Final Edition (Also Applicable to Evora)

Symptoms

A failed wheel speed sensor will typically illuminate:

• ABS warning light (permanently on)
• Traction Control warning light (permanently on)

Parts Required

• Replacement Bosch wheel speed sensor
  • Bosch Part Number: (A132J6001F, Wheel Speed Sensor, rear suspension // BOSCH 0 986 594 610)
• 8mm socket or spanner
• Jack and axle stands (or a lift)
• Lotus 20/20 Diagnostic Software and compatible interface, Link to guide, Lotus 20/20 diagnostic Software

Diagnosis

Before replacing any parts, use the Lotus 20/20 diagnostic software to identify which wheel speed sensor has failed.

The software will report the specific sensor (front left, front right, rear left or rear right), avoiding unnecessary replacement or investigation.

One particularly useful feature is that if the sensor is unplugged, the software can distinguish between an open circuit and a connected but failed sensor, making diagnosis much easier.

Confirming the Fault

If you want to be absolutely certain that the sensor itself has failed (rather than the wiring or ECU), a simple test is to swap it with the corresponding sensor on the opposite side of the car.

For example:

• Remove the suspected faulty front left sensor.
• Swap it with the working front right sensor.
• Reconnect both sensors and read the fault again using Lotus 20/20.

If the fault moves to the opposite side, the sensor itself is defective. If the fault remains on the original side, the problem is likely elsewhere, such as the wiring, connector or ABS module.

This quick test can save a lot of time chasing wiring faults and gives confidence that replacing the sensor will solve the problem.

Replacement Procedure

1. Park the car on level ground and safely jack up the affected corner.
2. Remove the wheel.
3. Recommended: Disconnect the vehicle battery before unplugging the sensor.
4. Locate the wheel speed sensor on the hub assembly. The sensor is retained by a single 7mm bolt and has a cable leading into the hub.
5. Remove the 7mm retaining bolt.
6. Carefully withdraw the old sensor from the hub.
7. Fit the new Bosch sensor into position.
8. Reinstall the 8mm retaining bolt and tighten securely.
9. Reconnect the electrical connector.
10. Reconnect the battery.
11. Refit the wheel and lower the vehicle.

Verification

Reconnect the Lotus 20/20 software and check for any stored fault codes.

In most cases the ABS and traction control warning lights should extinguish once the new sensor is recognised. If necessary, clear any stored fault codes and perform a short test drive to confirm normal operation.

Notes

• This procedure is applicable to the Lotus Exige 390 Final Edition and is believed to be valid for Evora models using the same Bosch wheel speed sensor arrangement.
• Diagnosing the fault with Lotus 20/20 before replacing parts can save significant time. Without it, distinguishing between a failed sensor and damaged wiring can be difficult.
• In my case, unplugging the sensor was immediately detected by Lotus 20/20, demonstrating that the software can differentiate between a disconnected sensor and one that is electrically connected but faulty.
• Swapping the suspected faulty sensor with the equivalent sensor on the opposite side is an excellent way to prove whether the sensor itself has failed before ordering a replacement.

If your ABS and traction control lights suddenly appear together, don't immediately assume the worst. A failed wheel speed sensor is a relatively simple and inexpensive fix once correctly diagnosed.