The automatic gearbox of the Citroën C5 slips under acceleration, shifts jerkily between gears and increases fuel consumption. These problems occur mainly with older examples and cars with higher mileage. Kickdown responds slowly. Sometimes kickdown stops responding altogether. Do you recognise these symptoms? Read on to discover what the causes are and what you can do about them.
Why is the automatic gearbox of my Citroën C5 slipping?
Slip in the automatic gearbox occurs when there are problems with the coupling between the engine and the wheels. The drive is no longer transmitted correctly. You mainly notice this when accelerating: the revs rise, but the car barely moves forward. The Citroën C5 with automatic gearbox suffers from this more often than you might expect.
The main causes of slip are:
- Too little or contaminated transmission oil
- Insufficient oil pressure due to internal leakage
- Worn clutch plates or friction materials
- Defective solenoid valves that do not regulate the hydraulic pressure correctly
On older models of the Citroën C5 you mainly find the AL4 automatic gearbox. The AL4 is a four-speed gearbox that is also called the DP0. This four‑speed unit is known for being sensitive to oil quality. As soon as the oil is too old or too contaminated, the hydraulic pressure drops and the gearbox starts slipping. In later generations the Aisin six‑speed automatic is used. This gearbox is less vulnerable. However, the Aisin is not immune to similar problems.
Jerky gear changes with the Citroën C5 automatic gearbox
Jerky gear changes are common. The transition from first to second gear in particular feels abrupt and uncomfortable. When the engine is cold, the jerks are often even stronger than when the car has warmed up.
This behaviour can have several causes:
- Contamination in the valve body (the component that controls oil pressure), causing the hydraulic actuation not to operate smoothly
- Worn or sticking solenoids (electrically operated valves) that shift too late or too abruptly
- Software that deliberately shifts later with a cold engine in order to bring the engine up to temperature more quickly
- Internal wear in the clutch or friction discs
Owners report that the jerks can be mild at first. The shocks then only occur with a cold engine. If you do nothing, they often get worse and also occur with a warm engine. By that point there is usually already mechanical wear that can only be resolved with an overhaul or replacement.
Increased fuel consumption due to automatic gearbox problems
A slipping or jerky automatic gearbox often leads to higher fuel consumption. This is because the engine has to work harder to move the car forward. When the gearbox is slipping, the engine speed remains unnecessarily high, even if the speed stays constant. With jerky gear changes, each shift takes longer and more energy is wasted.
In addition, a defective automatic gearbox can keep the engine in a lower gear for longer. This is unnecessary. It increases fuel consumption by an average of 10 to 20 per cent, depending on the severity of the problem. A slipping gearbox is therefore noticeable not only in the driving behaviour, but also at the fuel pump.
Kickdown does not respond or is slow
The kickdown function ensures that the automatic gearbox quickly changes down when you fully depress the accelerator pedal. This is useful when overtaking or pulling away quickly. With a healthy automatic gearbox, the unit responds immediately and changes down within a second. With a worn or contaminated gearbox this reaction does not happen. Sometimes it takes several seconds before it changes down.
Possible causes are:
- Contaminated or worn transmission oil that delays pressure build‑up
- Defective kickdown switch in the accelerator pedal
- Electronics that do not communicate properly with the transmission control unit
- Blockage in the hydraulic system
If kickdown no longer works, this is not only annoying but also dangerous. Overtaking manoeuvres take longer and you have less control over the car’s power. Have this investigated quickly.
How do I flush the automatic gearbox of the Citroën C5?
Flushing the automatic gearbox means not only replacing the oil, but also thoroughly flushing the entire hydraulic system. The hydraulic system is the system that pumps the oil around under pressure. Flushing is often done with a special flushing machine that pumps fresh oil through the automatic gearbox while the old oil is drained. The aim is to remove all contamination, wear particles and old oil.
A standard oil change replaces about 40 to 60 per cent of the total oil quantity. The exact amount depends on the method (draining through the drain plug or via the cooler). The remainder stays behind in the cooler, valves and torque converter. Flushing removes these remnants and gives the automatic gearbox a thorough refresh.
Pay attention to the following points when flushing:
- Always use the correct ATF specification for your gearbox
- Have the flushing carried out by a garage with experience of Citroën automatic gearboxes
- Check whether there are filters present and have them replaced
- Drive gently for a short period after flushing and check whether the gearbox shifts smoothly
In some cases, flushing can temporarily make a worn automatic gearbox work better again. But if there is already mechanical damage, flushing will not solve the problem. That is why a thorough diagnosis beforehand is advisable.
Is automatic gearbox repair on the Citroën C5 expensive?
The cost of repairing the automatic gearbox depends on the nature of the problem. An oil change including filter costs on average between 200 and 400 euros. Flushing with a flushing machine comes to 300 to 600 euros. Replacing the valve body or solenoids can run up to 800 to 1,500 euros, depending on the brand of parts and labour costs.
In the event of serious internal damage, a complete overhaul or replacement is necessary. A refurbished automatic gearbox costs on average between 1,500 and 3,000 euros, including installation. A brand‑new gearbox is often not available or extremely expensive, which is why overhaul is the most common option.
Preventive maintenance is therefore sensible. Regularly renewing the oil keeps the hydraulic pressure up to standard and prevents internal contamination. This significantly extends the life of the automatic gearbox. Replace the oil every 60,000 to 80,000 kilometres, even if the manufacturer does not specify this. This considerably extends the lifespan and prevents small problems from developing into costly repairs.
Practical tips for buyers and owners
If you are considering a used Citroën C5 with an automatic gearbox, always ask for the transmission’s service history. Check whether the oil has been changed recently and whether any repairs have already been carried out on the valve body or solenoids. Take a thorough test drive, both with a cold and a warm engine, and pay attention to shift points, slip and jerky behaviour.
During a test drive, check the following:
- Smooth shifting under gentle acceleration
- No thump when engaging D or R
- Immediate response to kickdown
- No warning lights or error messages
- No burnt smell from the oil
For owners, the rule is: do not ignore minor complaints. An automatic gearbox that occasionally shifts jerkily can turn out to be much more expensive later if you wait too long. Have fault codes read professionally with diagnostic equipment (code‑reading equipment) that is specifically suitable for Citroën. Not every generic code reader provides sufficient information about transmission control.
On the Carnews website you will find much more information about other common problems with the Citroën C5 and other models. Discover useful tips, practical guides and experiences from car enthusiasts to help you with the maintenance and purchase of your car.
Frequently asked questions
Typical symptoms are jerky, harsh or illogical shifting, especially with a cold engine, and a thump when engaging D or R. Going into limp‑home mode (staying stuck in one gear) and warning messages on the dashboard also point to problems. In addition, slipping, hesitation when pulling away or changing down, and a burnt smell or very dark automatic transmission oil can be signs of a defective gearbox.
The most common causes of automatic gearbox problems in the Citroën C5 are aged or contaminated transmission oil, pressure loss in the hydraulics, wear or contamination of the valve body and faults in sensors or electronics. This often manifests itself as jerky shifting, limp‑home mode, fault codes and slow or illogical shift behaviour, especially with a cold engine. The older 4‑speed AL4/DP0 automatic gearbox has the worst reputation and is notorious for jerks, limp‑home mode and warning messages. The later Aisin 6‑speed (AM6) is seen as more robust and refined, but can also develop problems if the oil is not changed correctly and on time.
Possible repair options for a defective automatic gearbox of a Citroën C5 are: changing or flushing the automatic transmission oil (optionally including a second change shortly afterwards), overhaul or replacement of the valve body and solenoids, software update/diagnostics and repair of electronic components, or a complete overhaul/replacement of the automatic gearbox. A simple oil and filter change typically costs roughly €250–€450, depending on the method and the oil used. Repairs to the valve body/solenoids or targeted hydraulic/electronic repairs are usually in the region of €500–€1,200. A full overhaul or exchange gearbox often costs between about €1,500 and €3,000, depending on the type of gearbox, the damage and the specialist.
Change the automatic transmission oil preventively and at a shorter interval than “lifetime”, preferably via a specialist with experience of Citroën C5 gearboxes (AL4/Aisin) who uses exactly the specified ATF. Have fault codes read periodically with brand‑specific diagnostic equipment so that early faults in sensors, solenoids or the valve body are detected at an early stage. Do not ignore small jolts or hesitant shifting, but have the gearbox checked immediately to limit further wear. Regularly check for oil leaks, unusual smell or colour of the oil and have any suspicious signs assessed straight away.
With a Citroën C5 automatic gearbox, it is usually not advisable to start tinkering yourself or to try to “repair” things at random, because the gearbox is very sensitive to the wrong oil, incorrect filling methods and incorrect diagnosis. What you can do yourself is take a test drive, observe the shifting behaviour and have basic checks carried out, such as checking oil condition and having fault codes read. The real diagnosis of the valve body, oil pressure and electronics, however, requires brand‑specific or automatic‑gearbox‑specialist equipment and experience. In practice, it is therefore wiser to go to an automatic gearbox/Citroën specialist as soon as possible instead of experimenting yourself.