Adventures with a Xantia VSX and a C5 v6

[octinum]

Ah, does blink code work for Hydractive? I saw some resources using it for reading engine error codes, but not Hydractive.

I think it was something like shorting a pin (C2, IIRC) for x seconds, then watching the engine check light blink. I'll find the source and give it a try. The Lexia I have doesn't have the connector for Series 1 (I previously used it to diagnose my old C5), and it's the first time I'm hearing about "Elit" reader. thank you!

The suspension should go into soft mode when the car is stationary with the engine running, regardless of the dynamic sensors (steering angle and suspension movement), so you can initially ignore them (and the speed input sensor).

The first thing to check are the 2 power voltages (constant and ignition switched). Beyond that, it is most efficient to get the ECU codes. If you don't have a Lexia or Elit code reader, the hydractive ECU codes can be read with a simple blink code reader.

[xantia_v6]

I beleive that the hydractive ECU supports blink code reading, but needs an external LED on the line, not the built-in warning light. But if you have a lexia with a 16 pin connector, then you should be able to jumper to the appropriate pins on the 30 pin connector for the hydractive ECU.

See: viewtopic.php?t=49045

[xantia_v6]

After thinking about it, maybe the best thing for you to do is to get a 16 pin obd connector from another car and wire it into the car using the link above as a guide.

[octinum]

Thank you xantia_v6!

A bit of progress in terms of diagnostics: Constant and Ign. Switched fuses are working. I also tried cutting the external diode to the front electrovalve and I heard the "clack!" this time, at least what I think is the EV click. I'm assuming the diodes the previous person who worked on the car are also dead. Then again, the car is still in stiff mode; I sat on the front side and it only moves a couple centimeters or so.

This, I think, can point to a few causes:
- Dead diodes: According to the datasheet, VN05N SSRs in the Hydractive control unit have thermal shutdown feature. If the diodes are dead, VN05N temperatures would increase, causing shutdown (even if they aren't fried yet). Good news is, I should have some backup VN05Ns somewhere, and I have a spare Hydractive control unit I can work on. Bad news is that; I can't find either. So first thing to try is to fit proper diodes with high breakdown voltage specs.
- Dead VN05N or hydractive control unit: Should be quite rare to see the Hydractive control unit dead. VN05Ns are a more probable suspect.
- Spheres. I'm not hearing a lot of "clicks" from the regulator, but the center spheres might be low on pressure. I think the electrovalves need a certain pressure differential to work; the solenoid allows a "low power" valve which in turn activates the "main" valve which allows LHM to flow. So if that first "small" valve cannot work due to low pressure, the actual mechanism that allows LHM to flow wouldn't also work
- Internal leak in the electrovalves. That is the horror scenario. I'm not good at mechanical things, and I don't think I can find anybody who could work on the valves without killing them. Let's hope it doesn't come to this.

[xantia_v6]

Measure the voltage on each electrovalve when it should be in soft mode. If the electronics are correct, you will see a few volts (3V to 6V) continuously. If you see voltage for a second or so that then diappears, then there is probably as faulty diode or solenoid. If there is no voltage at all, then it would indicate a problem inside the ECU.

A leaking electrovalve is not too difficult to repair if you treat it carefully.