2-Tronic Gearbox

 see here for the MA gearbox mechanics 

 "Automatic Gearbox Fault"  - "auto" and "snowflake" flashing 

 see here for excellent thread on how 2-tronic works 

this is a Citroen C2Club thread; you may need to register to see

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 five years and over 24,000 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

Mysterious unable to get one gear on autos:

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.

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 ten 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.

On test, the battery and alternator appear to be perfect. This is a suggested mechanism of failure:

You can get a similar effect sometimes when manoeuvering a manual car around a car park. If you let the engine revs drop too far when engaging the clutch, the alternator cuts out (as it should). The battery volts suddenly drop from 14.3 to 12.3 volts which causes the ECU to hiccup and you can feel the engine jerk and go lumpy; occasionally it can stall.

Now relate this to higher speeds - if the alternator momentarily stops charging for any reason, battery volts instantly drop, the ECU hiccups and on an Auto it messes up the gear changes and signals an auto gearbox failure indication.  The car coasts to a halt

Two minutes later the alternator cools a bit, comes good and you can drive normally and wonder what happened?

This is rather like the early stages of starter motor failure - it is well-known that a starter motor can fail to operate when hot but work perfectly next morning.

We have Lucas; Peugeot have . . . .

Commentary:

 also see - this copied page from Eurocarcare 

The actuators work very hard - where there is noise there is wear is a good adage. Perhaps the clutch actuator is getting slow in its old age (after all, most are now 8 years old and the grease they use has a SHELF life of only 5 years) and/or maybe the gear actuator is slowing down.

They have to operate very quickly in order to fall within the time window set by the electronics. If the operation isn't completed a fault flags up; with possibly greater frequency as the actuators get hotter in traffic.

It does appear that the gearbox/ecu/actuator system gives one or two warning shots before failing completely. The actuators take short bursts of very high current so a resistance as little as 0.1 ohm can drop the voltage to the actuator motor by 2-3 volts - so the actuator motor only sees 9 volts; runs slow and misses the time window.

It seems the next stage can be to kill the engine possibly leaving you in a dangerous situation.

Had it left you stuck in one gear (so you could at least drive off the carriageway) it would be relatively safe, but to kill the engine should be a no-no.

Perhaps this needs reporting to VOSA as clearly this is becoming a safety issue on these transmissions as they age.

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

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

  * * * see here for a dismantled Gearbox Actuator * * *  

  * * * see here for a dismantled Clutch Actuator * * *  

 possible source for REPAIRS to GEAR and CLUTCH ACTUATORS 

Neena says:  this is interesting. I have called them today and they quoted £50.00 to test/diagnose per unit, mentioning that gear actuator often goes as a consequence of clutch actuator...is this true? Therefore testing of both parts would equate £100

Thereafter a max of £250 to repair each, with no reprogramming required. Lifetime warranty on work too. Hmm... I wonder what they are doing to fix the part. We need to learn! Thanks for posting this. I am unsure as to the reliability, however all in all cheaper than the usual big P.