2-Tronic Auto Gearbox

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Loud clicking and death groan from gearbox

On hot days you may well have been driving with your windows open and heard that terrible death groan.

As long as the gearbox is working OK, DO NOT WORRY - this is normal. The clicking noise is three high power motors doing the gear changing; the death groan is the big return spring in the clutch actuator rubbing against the support inside the clutch actuator.

Mine has been doing exactly this for the last seven years and over 30,000 miles to my knowledge and probably before that. Live with it!

Few mechanics know as much about these cars as we do!

Legally - the 2-Tronic is an Automatic Gearbox

This is from the DT1 form given to DSA examiners and this is what the official guidelines state regarding automatic transmissions:

6.8 VEHICLES WITH AUTOMATIC TRANSMISSION

A vehicle with automatic transmission is defined in regulations as `A vehicle in which the gear ratio between the engine and the wheels can be varied only by the use of the accelerator or brakes'. In general a vehicle without a manual clutch is regarded as an automatic.

and specifically for semi-autos:

SEMI-AUTOMATIC SYSTEMS

With these the driver has to select the gear required by movement of the gear lever as with a manually controlled gearbox, but there is no clutch pedal. For driving test and licensing purposes these vehicles are regarded as automatics.

It has been said that only "Planetary" gearboxes can be automatic. This cannot be true as Planetary is a specific type of automatic gearbox. That definition omits the CVT (continuously variable ratio) boxes; our electrically operated automatic boxes; the swash plate; Hobbs and Hayes transmissions (to name a few) - all of which can be fully automatic. More recently; electric cars (and hybrids) are fully automatic in operation.

The 2-Tronic Gearbox (also known as the Citroen "Sensodrive")

is a conventional gearbox electrically operated via two special actuator units controlled by an electronic control unit

These operate the clutch and select the gear automatically (or can be manually selected)

the skeleton drawing shows the basic layout of the components.

an ECU (right-hand side) controls the clutch actuator (bottom right) and the gear selector (top centre) to provide a fully functional automatic functions

There is a switch inside the car which gives manual control, though it won't let you rev the engine too high or too low and the ECU takes over to prevent damage to the engine.

this is the wiring synopsis for the controls and actuators of the auto gearbox.

and this is the detailed wiring schematic for the controls and actuators of the auto gearbox. The coloured wires are the CAN/VAN circuits (legend in synopsis drawing above)

still can't see the detail? - try double-clicking: the drawing should then open in a browser window that can be zoomed

Another possible problem might be corrosion inside the in-line fuse-holder.

This in-line fuse is hidden under the air filter box and/or battery box. The fuse is unlikely to blow, BUT any corrosion could affect the supply to the gearbox ECU, as Chris Holmes discovered.

The small in-line fuse box is on the end of a piece of cable conduit and can be manipulated to become more visible. There is a 30amp fuse and the contacts on his were corroded. Chris cleaned it, and the socket on the fuse box, and rerouted it so it sits by the rear left of the battery box.

Just think that 30amps flowing through just 0.1Ω contact resistance will instantaneously drop 3volts so depriving the gear actuator of the full voltage it needs to operate quickly.

This alternative fuse for the ECU is mounted, on its own, on top of the gearbox. Access after removing the air filter box. This (possible replacement) appears to be secured in place.

Full 2-tronic (Sensodrive) gearbox information

Mysterious unable to get one gear on autos:

First sign of a problem is often the inability to select reverse - but assuming you have remembered to press the brake pedal when selecting reverse, check the actions below:

Peugeot 1007 2-tronic auto; 67,000 miles - doesn't seem to be selecting 4th and then flashes up automatic gearbox fault. A garage has quoted £700 not sure what for?

My reply:

Garage won't know so their estimate will almost certainly be a guess.

Fault could be in the gearbox - unlikely - no record of gear failures
Or in the clutch actuator - unlikely as it is OK in the lower gears
Or in the gear actuator - possible but these are generally very reliable
Or in the ECU - but again these are usually very reliable (but be aware of overheating problem)
Or the ECU fuse (see above)

Most common fault is a low or dying battery - when a gear change occurs, three powerful motors have to work very fast to change the gear and it has often been found that the extra load will drop the battery voltage momentarily and kill the change.

Secondly - maybe one of the connectors has minor corrosion on the contacts - it only takes a fraction of an ohm to drop the voltage enough to prevent the change occurring in the very short time interval allowed (see bottom of this web page)

A German board suggests that others have had the same problem and often aged grease in combination with bumpy roads were blamed. The grease in these actuators has a shelf life of 5 years - and our cars are all twelve years old give or take the odd year.

May be coincidence, but for reasons I won't go into, 5 years ago I sprayed WD40 over the vertical gear selector rod and end of the gear actuator - and have not had any trouble (so far) with gear selection

Neil Gibson reminds us that: what you might think as a transmission problem could be a symptom and not the cause.

Each electronic control unit feeds data via the BSI unit or body control module to the gearbox. A momentary glitch can have interesting results.

A recent problem with an ABS pump resulted in the sliding doors failing to open. Why should the ABS impact on the doors? The door control module won't allow operation above 3 mph. No speed reading. No door opening. The doors get blamed again!

The gearbox is the same. Virtually every power train sensor from throttle position to wheel speed can affect gear selection

Mysterious loss of all gears on autos:

Very occasionally the car can be going well and suddenly you lose all gears for no apparent reason and the car coasts to a halt with "Automatic Gearbox fault" showing on the multi-screen. Five minutes later the car can be restarted and all appears well.

Very often, a new battery can cure the problem for a while, however sometimes the problem recurs.

Be aware that a component inside the gearbox ECU (mounted on the side of the gearbox in a hot area) can overheat especially in heavy traffic with prolonged stops. In these circumstances, it can help to flick the gear into neutral at every prolonged traffic stop.

Mysterious loss of all gears on autos: longer explanation

If the temperature is above 20°C and you drive in heavy traffic, then this seems to be a common problem. It was first reported from South Africa, which has hot summers - but there are many more reports now as they age. Most likely is that something electronic inside the gearbox ECU is overheating; no-one has yet come up with a cure for this.

It seems to help if you flick the gear into neutral at every prolonged stop, (eg traffic lights or right turns in the UK).

Some have moved the ECU off the gearbox mounting to a position up by the radiator (I understand the cables will allow for this) - but I haven't heard if this solves the problem.

Less reported has been the gear change actuator has tight tolerances that causes it to tighten up when it gets hot and so misses the gearchange window. It may be that this problem has been cured in later actuators.

So far, there has been no definitive cure as far as I am aware.

Problems with the gearbox or clutch actuators?

Thunder says: The gearbox ECU is right under the battery box bolted to the front of the gearbox. The rubber boot on the electrical wiring can perish and the connectors are quite low to the ground so can get water in

Clean contacts with electric circuit cleaner and then spray with a silicone spray and then use some silicone sealer to seal hole and wires were they go in

And again: do check out the connectors on the motors and the ECU first as these are known to corrode (earlier models had poor seals, now replaced by better ones)

for the ECU: Seal for 48-pin connector: part number: 2530 64 (red) - Seal for 32-pin connector: part number: 2530 63 (blue) - 4 x ECU mounts part number: 2210 84 - Contact spray part number: 9731 2C note: these are Citroen numbers, Peugeot don't list separately

Turn off ignition and wait 5 minutes for electronics to settle.
Disconnect battery.
Disconnect both connectors from gearbox ECU and push the brackets back to remove old seals.
Remove the ECU from the gearbox (by cutting the four ECU mounts)
Inspect connector pins ECU for moisture and rust.
Replace the ECU if connector pins are corroded.
If only moisture in the ECU connectors dry carefully with hairdryer (max 800 watt - min 15 cm distance).
Clean connector pins with Contact Spray.
Place 4 new ECU mounts on the ECU bracket and check for secure attachment.
Remove old seals from connectors (one blue, one green).
Clean both connectors with Contact Spray.
Fit new seals, taking care they fit well.
Reconnect and check for good sealing.
Reconnect battery.