Citroën Reverse Light and Parking Sensor Stopped Working? A Guide to Fixing It at Home

If you put the car in reverse gear Citroën C3, Aircross or Basalt If nothing happens — the light doesn’t turn on and the parking sensor doesn’t beep — you have an immediate safety problem. Besides the risk of collisions, you could be fined for driving with burned-out bulbs.

This is a frequent technical defect in the Stellantis/Citroën line and, most of the time, the culprit is not the bulb, but a small part called Reverse switch.

The Problem

The symptom is twofold: the rear white lights remain off, and the parking sensor (if your car has one) does not activate the screen or sound. This indicates that the car’s electronic control unit does not “know” that you have engaged reverse gear.

How does it work?

There is a small switch (reverse switch) screwed directly onto the gearbox. When you move the lever into reverse, an internal rod presses this sensor, closing the electrical circuit that sends power to the lights and the parking sensor module.

Why does the defect occur?

There are three main causes for this “rear blackout” in Brazil:

1. Connector Oxidation: Since the sensor is exposed on the underside/side of the engine, mud and moisture can oxidize the pins, preventing the passage of electricity.
2. Part Wear: The internal spring of the switch loses its strength or the metal tip wears down, ceasing to make contact.
3. Blown Fuse: A short circuit in one of the taillights may have triggered the protection system.

Tidying Up (Step by Step)

Before spending money on an electrician, try this procedure:

1. Contact Cleaning: Locate the sensor (it’s on top of the gearbox, accessible from above on many C3 models). Disconnect the plug and apply the spray. Contact Cleaner. Replace and test.
2. Sensor Test: With the car running (ignition only), disconnect the plug and make a “bridge” (jump) with a piece of wire between the two pins of the connector. If the reverse lights come on, the problem is the sensor, which needs to be replaced (it costs around R$80).
3. Replacement: The replacement is simple: just unscrew the old part (usually a 22mm wrench) and screw in the new one. There’s no need to drain the transmission fluid.

Protection Fuse

If the “bridge” test above didn’t work, the problem is the fuse. In the new Citroën line (C3/Aircross/Basalt), the reverse and auxiliary circuit is protected by the internal box.

• Related Fuse: Check the fuse. F12 or F21 in the internal fuse box (below the dashboard).
• Amperage: Generally 10A (Red). If it is burned out, the reverse lights and other driver assistance sensors will not work.

Expert Tip

Verdict: If you recently installed a non-original backup camera and the reverse light stopped working, the installer likely used a “switch” that overloaded the circuit. In these cases, the fuse blows to protect the BSI control unit. Always prefer video interfaces that don’t cut original wires.