Topic: Where does speed signal come from? (Read 3683 times)

VR4Dave · « **on:** 28 October 2010, 17:20:03 »

Hi, got a weird problem. Thought I needed to replace my servotronic relay for power steering as sometimes i get full assistance and sometimes limited, I know it's not a pump problem.

However i noticed today that speed dependant volume is not working nor are any of the speed dependant calcs for economy, trip distance etc.

Speedo, abs and traction control all work fine, any ideas?

Dave

Kevin Wood · « **Reply #1 on:** 28 October 2010, 17:47:58 »

They should all be on the same signal from the ABS/TC ECU. I wonder if there's a break in the connection somewhere?

Kevin

TheBoy · « **Reply #2 on:** 28 October 2010, 18:53:53 »

does the speedo die at any point?

VR4Dave · « **Reply #3 on:** 28 October 2010, 19:15:05 »

does the speedo die at any point?

No, speedo is fine even during the low steering assistance episodes.

ECU was replaced in Jan this year by previous owner (I have the bill for £1150 ouch!)

TheBoy · « **Reply #4 on:** 28 October 2010, 20:00:35 »

Meter time then!

VR4Dave · « **Reply #5 on:** 28 October 2010, 20:43:22 »

Haven't got a clue where to start with this, I'm ok with spannering but not good with car electrics.

Where is the abs ecu? I'll at least check everything's physically solid.

Kevin Wood · « **Reply #6 on:** 29 October 2010, 09:36:58 »

Quote

Haven't got a clue where to start with this, I'm ok with spannering but not good with car electrics.

Where is the abs ecu? I'll at least check everything's physically solid.

If the signal's reliably getting to the dash, I'd say the ABS ECU end is fine and the problem is under the dash, as that's where the servotronic box is.

Kevin

Kevin Wood · « **Reply #7 on:** 29 October 2010, 09:38:06 »

On another tack, do you have the original stereo fitted, or aftermarket? Just wonder if the stereo is loading the signal.

Kevin

Dave DND · « **Reply #8 on:** 29 October 2010, 09:56:50 »

If prodding around for a speed pulse signal, an old fasioned analogue meter is often easier to use than a digital one for this purpose, as the pulse can be so brief that a digital meter may not react in time.

Set to 12V, and push the car forwards or backwards a few feet whilst monitoring the speed pulse wire, and you will see the analogue meter swing quite clearly.

Each model of car is different, but "generally" speaking a speed pulse signal will be between 5V and 8V and will pulse every couple of meters of distance travelled.

Kevin Wood · « **Reply #9 on:** 29 October 2010, 10:18:34 »

Agreed.

The signal wire is Blue with a Red tracer on an Omega, if I'm not mistaken.

Most systems that receive the signal can report it in their live data if you can get it to a tech 2. Still doesn't tell you where the break is, though, because there's no telling how the wire is routed.

Continuity check between the systems is probably the best way.

Kevin

Kevin Wood · « **Reply #10 on:** 29 October 2010, 10:27:59 »

Signal is routed to the following systems, as far as I can see (if fitted):

Source: ABS ECU

Engine ECU
Instrument Panel
Climate Control
MID/TID/CID/GID
Radio / Nav system
Servotronic ECU
Headlamp Levelling
Suspension self-levelling
Sunroof

Wiring to the headlamp levelling ECU (in the driver's side front wheel arch) does sometimes chafe through. Might be worth a look.

Kevin

Andy B · « **Reply #11 on:** 29 October 2010, 12:30:34 »

Quote

....

The signal wire is Blue with a Red tracer on an Omega, if I'm not mistaken. .......

It definitely was in a Senator

TheBoy · « **Reply #12 on:** 29 October 2010, 17:40:37 »

Its around 25,000 pulses per km, so 25 pulses per m (about 2/3rds of a wheel revolution) so a digital meter will defo struggle as Dave DND says.

Kevin Wood - I have seen a failed ABS, yet speedo worked (nothing else did - MID, cruise, SDVC on radio etc). Can't explain that. Didn't make sense to me at the time, and I promise I hadn't been drinking

VR4Dave · « **Reply #13 on:** 30 October 2010, 08:25:59 »

Thanks for all the info so far. Speedo is original, cruise control works fine, satnav a bit hit and miss - it knows where I am to start a journey and calculates a route but then doesn't recognise that I've started moving.

Kevin Wood · « **Reply #14 on:** 30 October 2010, 11:46:55 »

Quote

Its around 25,000 pulses per km, so 25 pulses per m (about 2/3rds of a wheel revolution) so a digital meter will defo struggle as Dave DND says.

Kevin Wood - I have seen a failed ABS, yet speedo worked (nothing else did - MID, cruise, SDVC on radio etc). Can't explain that. Didn't make sense to me at the time, and I promise I hadn't been drinking

I'm guessing the different devices have different thresholds as to where they see a transition of the signal, so if the signal were becoming weak due to a failing connection in the ABS ECU I can see why it might affect some items before others.

Would be good to get a scope on it perhaps? :-/

(he said, forgetting that "normal" people don't have 7 of them in their loft).

Kevin

VR4Dave · « **Reply #15 on:** 30 October 2010, 12:48:53 »

When I wrote speedo is original I did obviously mean stereo is original

Excuse my ignorance but what do you mean get a scope on it?

Andy B · « **Reply #16 on:** 30 October 2010, 13:25:09 »

Quote

Oscilloscope

School will be where most people last saw one.
http://en.wikipedia.org/wiki/Oscilloscope

Kevin Wood · « **Reply #17 on:** 30 October 2010, 14:19:54 »

Quote

Quote
School will be where most people last saw one.

.. and where I got the first one in my collection as it happens.

Kevin

Dave DND · « **Reply #18 on:** 30 October 2010, 16:21:22 »

Quote

Quote
Quote
School will be where most people last saw one.

.. and where I got the first one in my collection as it happens.

Kevin

me too !!

tidla · « **Reply #19 on:** 30 October 2010, 22:26:36 »

joint venture in bolivia maybe?

05omegav6 · « **Reply #20 on:** 31 October 2010, 05:44:10 »

speed signal is definitely blue with red trace. i use the sunroof one for a taxi meter. same for vectra c as well, though with can bus not all the blue/red wires give an analogue signal.

think the wire runs from the ecu to the trip computer/radio with feeds to the instrument cluster and sunroof. :-/
wiring diagram in the book of lies may shed some light on this. the loom in my 54 reg ex plod is almost identical to what the book shows for late model pre face lifts.

VR4Dave · « **Reply #21 on:** 31 October 2010, 14:17:39 »

The plot thickens.... today when driving, the radio randomly turned on by itself, the cid didn't come on with it. When I pressed the radio power button to turn it off the radio stayed on and the cid turned on, so now normal i.e. radio on and cid as should be with radio on.
I pressed the power button once more and it all went off as normal.

There is obviously something loose somewhere, still don't understand why it affects the power steering?

Will have the stereo out for a look.
Had the glove box out to look for servotronic relay, (I think this should be a red one) but I couldn't find it, there was only a grey one under there and a plug for one that is absent, grey base on that also. Is there anywhere else it could be?

Also, don't think it will help but won't do any harm I'm going to clean wheel sensors - where are they (please don't say on wheels

) and what do they look like?

Ta.

VR4Dave · « **Reply #22 on:** 01 November 2010, 16:56:44 »

Quote

The plot thickens.... today when driving, the radio randomly turned on by itself, the cid didn't come on with it. When I pressed the radio power button to turn it off the radio stayed on and the cid turned on, so now normal i.e. radio on and cid as should be with radio on.
I pressed the power button once more and it all went off as normal.

There is obviously something loose somewhere, still don't understand why it affects the power steering?

Will have the stereo out for a look.
Had the glove box out to look for servotronic relay, (I think this should be a red one) but I couldn't find it, there was only a grey one under there and a plug for one that is absent, grey base on that also. Is there anywhere else it could be?Also, don't think it will help but won't do any harm I'm going to clean wheel sensors - where are they (please don't say on wheels ) and what do they look like?

Ta.

Anyone?

Kevin Wood · « **Reply #23 on:** 01 November 2010, 18:49:01 »

Still scratching my head. :-/

I would get the stereo out and see if there's any signs of someone bodging the wiring for a start. I have occasionally had my head unit so something stupid like that though.

Wheel sensors are on the hubs for the front wheels and at the rear they are inboard, either side of the diff on the halfshaft flanges. They rarely give problems, however.

Kevin

Dave DND · « **Reply #24 on:** 01 November 2010, 19:09:45 »

Agree - puzzling . . . .

I would try removing the stereo, and see if the other symptoms remain, just in case the stereo is pulling the signal down ?

Then try unplugging the nav, and see what works / doesn`t.

:-/

VR4Dave · « **Reply #25 on:** 02 November 2010, 06:54:35 »

Cheers fella's will try running with stereo out today and report back.

Dave.

VR4Dave · « **Reply #26 on:** 02 November 2010, 14:59:55 »

Update:
Today I have full assistance on the steering at all speeds, whereas for the last week I've had the lower assistance level at all speeds.
The sdvc and cid speed related figures are still not working. I pulled the stereo out and it made no difference.
I did notice however that the "speed" on the cid which normally reads 0/mph (irrespective of actual speed) read f/mph a couple of times briefly.

Could servotroninc box/relay have an effect on cid readings or is the signal independant to the signal that controls pas?
I would change the relay if I could find it!

Kevin Wood · « **Reply #27 on:** 02 November 2010, 17:23:20 »

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I would change the relay if I could find it!

Up under the dashboard above the driver's footwell, IIRC.

Kevin

VR4Dave · « **Reply #28 on:** 09 November 2010, 14:11:02 »

Kevin / Dave DND, as you two seem to be the one's with the ideas on this one; I swapped the sevotronic relay from my '52 cd into the MV6 and something strange happened :-/
The MV6 which has been mainly giving limited steering assistance (i.e. high speed assistance at all speeds) is now giving full assistance (i.e. low speed assistance at all speeds)
The cd that I swapped the relay from works as normal.

The other thing I noticed, is that when I have a speed dependant function on the display I briefly get a reading such as "F"/mph which only occurs when decelerating and passing the 40mph mark, which I believe is the point at which the amount of assistance on the steering changes.

I wouldn't mind taking the car to someone to have a look but it's not the sort of fault I want to go to a local garage or dealer with, any suggestions?

Dave DND · « **Reply #29 on:** 09 November 2010, 14:18:29 »

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Kevin / Dave DND, as you two seem to be the one's with the ideas on this one

Sorry, my expertese is more with the audio side of things than the car itself - maybe worth seeing which Oofer is nearest to you with a Tech2 as I think you are a little too far for me to investigate this any further?

Kevin Wood · « **Reply #30 on:** 09 November 2010, 14:59:13 »

Bear in mind that Servotronic units are programmed with a level of sensitivity and your two might not be the same. There are several sets of sensitivity settings, the choice of which depends on the steering box according to Tech 2 so it's possible that you now have the "wrong" settings for your box or vice versa.

Each set of settings has 3 values that can be programmed for "Minimal assist", "Normal" and "Maximum assist", so your replacement unit might not have had the same settings and that could account for the difference in behaviour.

Having said that, something weird is going on. It sounds to me like the MID is losing the speed input temporarily now (Hence the "F" for "fail" in the display).

This could be something such as the ground signal for the servotronic (or anything else that sits on the speed signal) being poor, such that, when it starts consuming current, it drags the speed signal outside the normal range and prevents other devices from seeing it.

Does everything else behave if you completely remove the servotronic box? (note:steering will be heavy).

Kevin

VR4Dave · « **Reply #31 on:** 09 November 2010, 19:27:26 »

Thanks for the response both of you.
Will try driving without the relay in and see what happens, did drive it twice with a failed steering pump and that was bloody heavy!

Kevin, with regards to the fail signal basically if I have the cid set to show me fuel range I will have the miles displayed most of the time except when slowing down around the 40mph mark then I get the F briefly. If I have speed or mpg selected then I have "0" displayed most of the time with the brief F when slowing down as above.

VR4Dave · « **Reply #32 on:** 10 December 2010, 16:17:09 »

Update:
Right, driving without the servotronic box in made no difference, to the other things - just made me arms hurt!

However I had a problem the other day where driving at about 50 on a non slippery straight bit of road the TC light came on and I lost power (no throttle response) I assume cut by the TC. I couldn't deactivate the TC with the button.
Turned off car and restarted and fine. (posted the problem on general help "bloody weather")

Someone suggested speeding up to 60 and letting it slow to 40 on the over run a couple of times to reset. I did this and this is where I noticed that it is when doing this that I get the "F" instead of a zero on the display for mph, speed, isntant mpg etc.

Also now have a code 1500 throttle motor. I did some more research and found this posthttp://www.omegaowners.com/forum/YaBB.pl?num=1290263706

I think this could be my problem too given the fact that it's all so intermittent and I have no problems with cruise,speedo or abs.

How do I find a bad earth?

News:

Author Topic: Where does speed signal come from? (Read 3683 times)

05omegav6