Citroen C4 Aircross ECU/PCM

Used and VIN-specific, a C3 1.2 PureTech ECU is around R4,500 and a 1.6 THP unit around R5,500 through our network. Repair, where the board is salvageable, sits nearer R3,167. Before you buy either, have the wiring and the earths checked — a corroded connector or a bad earth produces the same symptoms and costs a fraction to fix.

No-start, erratic running, a spread of warning lamps that follows wet weather rather than mileage, and communication errors on a diagnostic scan. The timing is the useful clue: faults that appear after rain and clear after a dry week are water ingress, not electronics reaching the end of their life. On the C2 and C3, unplugging the connector and finding green corrosion on the pins confirms it in seconds.

Repair is often the better route. Specialists here rebuild the PureTech, Xsara and THP units for around R3,167 and — the part that matters — keep your original coding, so the car does not need reprogramming to the immobiliser afterwards. What defeats a repair is corrosion that has eaten through the circuit tracks themselves rather than just the connector. In that case it is a replacement plus a coding session.

Yes, always. New or used, the ECU has to be matched to the vehicle and synchronised with the BSI, the immobiliser and the keys, or the car will crank and refuse to start. This is routine work for a Citroen specialist with the correct diagnostic equipment, but it is not something to discover after the part has arrived. We match used units on exact part number to keep the coding as straightforward as possible.

Blocked drains, in almost every case. The scuttle tray under the windscreen has drain channels that carry rainwater away; leaves, grit and pollen block them, the tray fills, and the water finds the ECU and the pollen filter housing. A perished windscreen seal does the same thing more slowly. Clearing those drains once a year takes ten minutes, costs nothing, and prevents the single most expensive electrical failure these cars suffer.