Citroen Xsara HDI, problems with gearbox (AL4)

[mtkoskin]

Hello all Citroen owners out there,

Anyone out there who have had problems with AL4?

I've had few issues with the box and now the current one seems to be quite tricky.
Before, I had the usual problem with regulation pressure and changed the electro valves. The fault code about pressure doesn't occur anymore. That's good. At least all oil is now new.

Now, the box also had a fault code pointing to gearbox input speed sensor. I spent yesterday inside the motor bay and replaced the sensor. I measured the resistance of the original sensor after replacement and it seems to be OK. Also, live data from Lexias measurement environment still gives 0 Rpm for input speed almost at all times. Sometimes it shows some reading but most of the time the value is 0. This might be because some broken wiring between the sensor and the ECU. SEDRE told me that the ECU 1630 has pins 45 & 46 to connect the input speed sensor. So next job is to tear up the engine bay again and identify the correct pins in the ECU connector and test if the resistance is seen at ECU pins. If not the wiring is to suspect. Otherwise … the ECU … I don't want to talk about it …

Does anyone have any experience about this kind of problem? Any pictures showing the ECU connector, which pins are the ones to test this with?

Because the ECU doesn't receive correct input speed the transmission won't lockup. That is quite annoying…


Regards
Mikko

[mtkoskin]

I have an update to my own post.

The gearbox is now working quite perfectly. It was the wire connecting to pin 46 which was broken (pink wire). The ECU connector and the ECU itself has markings about the terminal/pin numbers, so it is quite easy to find correct wire. Also the other wire for the input speed sensor (terminal 45) was almost completely broken (green wire). I had to open the wiring harness all the way to the oil dip stick to find the broken part of the wire.

I used the old sensor plug to create a test harness. With it, it was a bit easier to test the harness. You could connect the multimeter and wiggle the harness/connector manually with both hands.

Now I have smooth gear changes, no slipping at all, Lexia is happy with engine speed and input speed (being the same at all times when driving) and it shows gears from second onwards do now lock-up.

I hope this helps someone with same kind of problems ...

[Mandrake]

Well done, excellent result.

I don't envy the job - although on paper finding a broken wire is simple electronic troubleshooting you could do with a multimeter, physically doing it on a car when the wires criss cross through the car in conduits in almost impossible to reach places can be nightmarish, especially when all the wires in a bundle are the same colour... (thanks Citroen )

Glad that it's all back to normal now.