Automatic gearbox fault

Q I have a 2007 Citroën Picasso 2.0 with the AL4 automatic gearbox. I changed the fluid at about 40,000 miles and, at about 75,000 miles, the ‘automatic gearbox fault’ light illuminated. My local garage checked it and said it showed lower pressure, so I changed the fluid again and this seemed to cure the problem for about six months.

The fault reoccurs on an average of once per week. It happens usually when accelerating hard and it then locks in third gear. If I stop and switch off, then restart the engine, everything works perfectly. The vehicle has now done 92,000 miles. WS Swann

A The AL4 box is known for electrovalve issues that allow the running pressure to drop – this is normally indicated by the ‘snow’ and ‘sport’ indicators flashing. The illumination of the ‘automatic gearbox fault’ with the gearbox locked in third gear indicates an operational abnormality, which also can be due to failing electrovalves. The earlier Acutex valves were replaced in later units by Borg Warner valves, which should be more reliable; the later valves can be fitted in earlier gearboxes, as long as the gearbox software is updated.

It appears many owners of vehicles with the AL4 gearbox recommend frequent oil changes at a recommended interval of 20,000 miles. It is also

strongly advised to only use the genuine Citroën fluid (part number 9736 22).

You mention that the problem usually occurs during hard acceleration. For this reason, I would suggest checking the coolant flow to the heat exchanger on the rear of the gearbox to ensure that the gearbox oil is being sufficiently cooled.

There are nine electrovalves within the hydraulic block, six of them sequence solenoid valves, and it may only be one that is causing problems. Getting the system read by a Citroën dedicated scanner should narrow this down, making a repair possible by replacing the faulty valve. The Citroën book time for removing and refitting the valve block is 2.4 hours.