Faulty Hydractive 2 sensor ? - solved

Mandrake · Unread post by **Mandrake** » 16 Jul 2007, 01:53

Hi All,

Just to throw a spanner in the works of my testing of the effect of air bubbles on the ride, it seems that my Hydractive system has developed an electrical sensor fault

I still have the electrovalve LED connected after more than a year and in that time the soft/hard electrical switching has been pretty flawless, but now it is staying in hard mode at all times above 25Km/hr

I first noticed a problem a few days ago where it seemed like the straight ahead calibration was out - this is something that can occasionally happen as the steering wheel sensor has no centre position (it's an optical chopper disc) and straight ahead is determined by computer heuristics.

The symptom is that for a while the car can be in hard mode while driving straight ahead, and yet soft when turning in a specific direction. After a minute or so of driving the computer figures out that the centering is wrong and recaculates the centre position.

That happened a few times over the last few days but since yesterday it is staying in hard mode permanently above 25Km/hr - every time I slow down below that speed it switches back to soft mode.

The speed sensor must be ok if it knows whether I'm above or below that speed, and the throttle sensor is still working too. When I get home I'll have a look at the fault tables to confirm it, but I'm pretty sure the symptoms point at a slightly dodgy steering wheel sensor which has now completely failed.

Two questions:

1) Has anyone removed or replaced this sensor before ? Is it hard to get to ? Do I have to disconnect and remove the air bag to get at it ? I presume so, and its not something I'm looking forward to. is it likely to be repairable or should I be getting hold of a new one first ? Any clues as to where the cable runs and where the plug connecting it is ?

2) I wonder how many other people have this problem ? Could it be a contributor to some peoples mysterious hard ride ? Below 25Km/hr and including during a manual bounce test the car would be in soft, but as soon as you exceed that speed you're stuck in hard mode.

I only initially noticed it because I have an LED permanently connected.

GRRR.....

Regards,
Simon

Unread post by **philhoward** » 16 Jul 2007, 06:22

I've only ever removed a VSX steering wheel and there were 2 slip rings under there (one for the airbag and one for everything else?) and have them both sitting around doing nothing if they're any use? PM me if you do..

If it is those, then surprisingly easy (apart from trying to line up the steering wheel to get at the 2 torx bolts for the airbag). The only precaution to removing the airbag is to disconnect the battery for a while first to make sure the airbag ECU is most definately dead and don't use a hammer!

Unread post by **RichardW** » 16 Jul 2007, 07:59

Don't fret the air bag - it's easy. Set the wheel at 90° with the engine running - this will allow you to access the air bag screws from behind without having to turn the steering with no assistance. Shut down, disconnect battery, have cup of tea

(I like this sort of car maintenance!). Now just undo the two screws from the back of the wheel - T30 IIRC - I needed to cut away some of the rubber material of the wheel so I could see what I was doing. You really need a small ratchet drive or similar - they are quite tight. Lift the bag away from the wheel and prise out the connector. The next challenge is disconnecting the PCB for the stereo - you need to lift up the pin in the clip away from the PCB, and give it a good wiggle. You need a 21mm deep socket to undo the nut, and my wheel needed a vary hard jarring from behind to free it off the splines - leave the nut on th last couple of threads to stop the wheel flying off, bashing you on the nose, and wrecking the wiring to the airbag rotary connector

Mandrake · Unread post by **Mandrake** » 25 Aug 2007, 07:04

Fixed !!

And it wasn't the steering sensor. (Luckily I realised before going to the bother of trying to remove the steering wheel etc)

It was in fact the front brake pressure sensor switch!

The problem had got progressively more frequent so I decided to tackle it today, and on a hunch I measured the brake pressure switch - this can be done by unplugging the black connector on the HA2 computer and measuring with an ohm meter between pin 11 and ground.

The switch contacts should be closed with the brakes released, and open circuit with the brakes applied hard. Well what do you know - it measures randomly between 2k and 5k when it should be closed, and open when it should be open.

Straight away I suspected a dirty plug on the sensor but the next job was to figure out where it is!! The book is not a lot of help, saying it's "On the front left of the engine subframe".

I left the beeper on the multimeter connected and went under the car (on ramps of course) and started tugging on likely looking wires and all of a sudden it came right - and I eventually found the sensor is accessible through the left hand wheel arch next to the steering tierod with a standard 2 pin wire clip plug as used all over the engine.

A good squirt of LPS1 and plugging it in and out a few times and it was 100% reliable. Where its located the plug is exposed to water splash from the wheel arch so I decided to put some grease in the plug as well for extra insurance. (Stupid place for them to locate it!)

Another problem bites the dust. I thought I would document this for anyone else that might run into the same problem.

The symptoms were the suspension switching to hard mode and staying there most of the time above 25Km/hr but switching back to soft below that speed.

It's easy to see why it would cause it - the computer would think you were driving along with your foot hard on the brakes all the time, and its designed to switch to hard mode during hard braking above 25Km/hr...

Regards,
Simon

pprado · Unread post by **pprado** » 25 Aug 2007, 14:19

Hey Simon, nice to see your problem is fixed!

Anyway I removed myself the steering at least 3 times. No problems with it. But to remove the steering sensor you´ll need to remove the shrouders and direction/windwashers controls "frame" IIRC.

Couple of questions:

1. Isn´t grease going to change the resistance? I thought of fitting some plastic around the union...

2. How is your LED setup? What resistor value did you put in series, diode, etc?

Once I put a 12v lamp but it´s awkward to leave the lamp anywhere in the panel. A LED would be much nicer!!

pprado · Unread post by **pprado** » 25 Aug 2007, 14:29

I also need to say it was PERFECT that you found it now. I´m going to the car to do my left droplink and will surely give it a look!!!

Unread post by **Peter.N.** » 25 Aug 2007, 18:24

Hi Pedro

Regarding your question about applying grease to electrical contacts. No, it wont generally increase the resistance because the pressure applied by the contacts is normally enough to break down the grease film. It will however prevent further corrosion, so is well worth doing.

Stempy · Unread post by **Stempy** » 26 Aug 2007, 15:11

Just to throw another spanner in the works, I went out to check my brake pressure sensor and found that has no plug connected to it, and seems like it never has had

There is a connector hanging loose around about the same location but it is totally incompatible with the connector on the pressure sensor! Now I have no complaints about the ride quality but if it could be made better then I'll have a go at mating the two together.

First off though I'll have to check that the loose connector is indeed connected to the HA ECU so I'll need to find out which pins on the ECU are the pressure sensor input. I know I have somewhere the ECU pinout but can't find it at present, when I do I'll check it out and report back.

Mandrake · Unread post by **Mandrake** » 26 Aug 2007, 21:07

Stempy wrote:First off though I'll have to check that the loose connector is indeed connected to the HA ECU so I'll need to find out which pins on the ECU are the pressure sensor input. I know I have somewhere the ECU pinout but can't find it at present, when I do I'll check it out and report back.

Psst.....check my second post again...

Also I can't be sure that the sensor is in the same location on a V6 - maybe it's not, but the pinout on the ECU will be the same.

Regards,
Simon

Stempy · Unread post by **Stempy** » 26 Aug 2007, 22:11

Pin 11 it is then

Mandrake · Unread post by **Mandrake** » 26 Aug 2007, 23:27

Peter.N. wrote:Hi Pedro

Regarding your question about applying grease to electrical contacts. No, it wont generally increase the resistance because the pressure applied by the contacts is normally enough to break down the grease film. It will however prevent further corrosion, so is well worth doing.

Hi Peter,

Thanks for responding to that - you're quite right, normal grease without solid additives, such as LS-EP 2 can be used without affecting the contact resistance as the contacts pierce the oil film giving metal to metal contact.

Just as importantly that specific grease is an extremely good insulator - as evidenced by the ability to use it on CRT anode caps

You don't want a grease that might cause resistive leakage across the contacts either.

On the other hand a grease with moly or graphite solid particle additives in it would be unsuitable as they coat the surface of the metals, and would get between the contacts raising the resistance.

As well as that graphite is a partial conductor and therefore a poor insulator and would cause leakage across the contacts. I don't know about moly additives but they may as well.

So the moral is just use a standard general purpose lithium grease with no fancy additives or solids.

Regards,
Simon

bernie · Unread post by **bernie** » 27 Aug 2007, 11:43

I'll have a check of mine but I can't find my hard copy of the pin connectors on the ecu.

Any one help?

Mandrake · Unread post by **Mandrake** » 28 Aug 2007, 00:14

bernie wrote:I'll have a check of mine but I can't find my hard copy of the pin connectors on the ecu.

Any one help?

Ive emailed you a copy.

Regards,
Simon

bernie · Unread post by **bernie** » 28 Aug 2007, 11:10

Mandrake wrote:
bernie wrote:I'll have a check of mine but I can't find my hard copy of the pin connectors on the ecu.

Any one help?
Ive emailed you a copy.

Regards,
Simon

Thanks Simon, but nothing received

Mandrake · Unread post by **Mandrake** » 28 Aug 2007, 11:57

bernie wrote:
Mandrake wrote:
bernie wrote:I'll have a check of mine but I can't find my hard copy of the pin connectors on the ecu.

Any one help?
Ive emailed you a copy.

Regards,
Simon

Thanks Simon, but nothing received

Hmmmmmm.

Sent again. Let me know if you don't get it again...

Regards,
Simon