ABS Light On and Speedometer Malfunction (Citroën C4)

In the most modern Citroën models (such as the C4 Pallas, Hatch and Lounge), there is no longer a speedometer cable or a speed sensor in the gearbox. The vehicle’s speed is calculated by averaging the readings of the… 4 ABS sensors of the wheels.

• The Real Problem: If one of the front wheel sensors fails or if the wiring harness breaks, the ABS control unit loses its rotation reference. As a result:
  1. The light of ABS/ESP It lights up.
  2. THE Speedometer It stops recording (it stays at 0 km/h or gives an error).
  3. THE Power steering It can become heavier or lighter than normal (since it is progressive and depends on the speed).
  4. THE Automatic Transmission (If present) it may enter emergency mode because it does not know the car’s actual speed.
• Common Causes: * Excessive dirt (iron filings) on the sensor.
  • Wheel sensor burned out (common after driving through flooded areas).
  • Wheel bearing incorrectly replaced (the C4 bearing has a magnetic surface that the sensor reads; if installed upside down, the ABS will not work).

Location of Protection (Fuses):

There are two main fuses for the ABS system, both located in BSM (under the hood):

1. F01 (20A): It powers the electronic control components of the ABS module.
2. MF01 (Maxi-Fuse 40A/60A): It is hidden in the lower part of the BSM and powers the ABS pump motor. If this burns out, the brake pedal will…