Deanxm wrote:
You may well be right but certainly hydractive one will not trigger hard mode without speed sensor input, there is only brake pressure switch, steering angle input, body movement and speed sensor, the ecu will remain in soft mode with ignition on and 0 speed for pressure equalisation during loading and unloading, you can wiggle the steering wheel and bounce the car as much as you want it wont trigger firm mode unless it see's a speed of over 8kmh? cant remember now, later H2 may have been able to tell if a sensor is open circuit or a dead short or if it is telling porkies, the speed sensor in early cars is fitted inline to the speedo cable above the gearbox at the bulkhead, if you unplug the sensor from the cable it is still connecetd electricaly but will not detect movement of the car, yes the speedo will not work unless you use a joiner or second speed sensor to plug in place but it will tell you very quickly if you have pressure problems or electrovalve driver issues.
Works fine with mine anyway, disconnecting the body movement sensor (mechanicaly from the arb) will also prevent switching to firm on undulating roads whilst giving firm mode in the corners but if your roads are really rough you do risk bottoming out on big bumps.
D
Sorry I had assumed the original poster was talking about a Xantia, which are all Hydractive 2. Hydractive 1 is a different beast and has quite different behaviours, so you could well be right on Hydractive 1.
On Hydractive 2 a faulty speed sensor is determined by inference - the main way is if the accelerator is depressed more than 15% for over 30 seconds and the speed sensor registers nothing, (no pulses) it is assumed to be faulty. So whether you disconnect it electrically or mechanically makes no difference, it is assumed to be faulty and the vehicle speed assumed to be 100Km/hr (low turning thresholds for the steering wheel before triggering hard mode etc) for safety. If the speed sensor starts working again for at least 20 seconds it will start believing its input again.
There are various clever ways to detect by inference faults in all of the various sensors by comparing the data from them and checking them for consistency and believability, all detailed at the table near the end of this document: (page 70)
http://homepages.igrin.co.nz/simon/imag ... ive_II.pdf" onclick="window.open(this.href);return false;
(alter the 'e' in citroen to the standard lower case e, and the C to lower case)
One sensor you can disconnect to keep the car in soft mode a lot more is the throttle sensor - I did this on my Mk1 Xantia for a few months and it prevents the car switching to hard on take-off from a standstill - the rear squats a lot more but at least you don't get that bumpity ride for 5 seconds every time you accelerate from a standstill over broken road surfaces. It also prevents it switching to hard when you stomp on the pedal at speed. (Albeit with more rear body squat obviously)
It has no effect on the car going to hard when braking or cornering though, which is good, and still safe. Nor does it affect the anti-roll bar sensor. So for anyone who prefers a softer ride more often and doesn't drive like a maniac the throttle sensor (plug up behind the accelerator pedal on the firewall) can be safely unplugged, the only real downside is a lot more squat under acceleration. On something like a V6 it probably wouldn't be a good idea to disconnect, as the squat is likely to be ridiculously bad if left in soft mode
I might try it for a few days for a laugh...