Reconditioned Citroën C4 Gearbox

Eight engine variants, four gearbox types: the faults that lead to replacement on the C4

On the Citroën C4, transmission problems tend to cluster around a few recurring issues depending on the gearbox family. The BMP6 — an automated manual gearbox fitted to the 1.6 HDi, 2.0 HDi and 2.0 petrol — is the most frequently reported source of faults: juddering during gentle driving, hesitant gear changes or refusal to engage a gear are typically signs of internal mechanical wear, distinct from actuator-related problems. On manual versions, the 5-speed gearboxes fitted to the 1.6 HDi (engine codes 9HX, 9HY, 9HZ, 9HP, 9HR) develop synchromesh wear over time, particularly on 2nd and 3rd gears. The BMP5 specific to the naturally aspirated 1.2 (engine codes HMZ, HN01, HN02, HNS, HNZ) follows a different pattern, particular to that small unit.

Diesel, naturally aspirated petrol or THP: gearboxes with no cross-compatibility between families

The C4 spans two decades (2004–2024) and a highly varied engine line-up. On the diesel side, the 2.0 HDi (RHF, RHR) is paired with either a 6-speed manual or a BMP6, with no mechanical commonality with the 1.6 HDi gearboxes. On the petrol side, the 1.6 THP (5FV EP6CDT, 5FX EP6DT) is coupled to a 5-speed manual, while the naturally aspirated 1.6 covers three engine code families — NFU/TU5JP4, 5FW EP6 and 5FS/5FV EP6 on the C4 II — which do not necessarily share the same gearbox despite having an identical engine capacity. The 1.2 PureTech (EB2DT, EB2DTS) can take either a 5- or 6-speed manual depending on the year and trim level: engine capacity alone is not enough to determine the exact reference.

What this means before you order

The engine code stamped on the block is the essential starting point, particularly for the 1.6 HDi, where the six recorded codes (including the grouped form 9HX/9HZ/8HX/8HZ/9HN) correspond to different fitments. For BMP6 units, the gearbox is supplied without the automated actuator: the mechanical assembly is replaced, while the original actuator is retained or dealt with separately. EDEN BOITES lists all of these engine variants, from high-volume diesels through to lower-volume versions such as the 1.4 VTi 95 (8FP) and the 2.0 petrol (RFJ, RFN).