Cruise control failure, erratic fuel gauge and speedo

UK forum for general and technical discussion about the Z3 roadster
Post Reply
dixie4
Joined: Sun 22 Jun, 2014 09:53
Posts: 11

  Z3 roadster 2.2i

Cruise control failure, erratic fuel gauge and speedo

Post by dixie4 »

I am a new member and I have searched the old posts but have failed in my quest for someone who may have had similar problems as mine. If I have missed something please would someone please point me in the right direction.

My car is a Z3, 2002, 2.2 with 38k on the clock that I have owned for 9 years and it has only been used in the summer.
It has never let me down in the past except for an irritating flat spot when changing gear. Back in May I decided to investigate this problem.
It turned out to be one of the soldered wires in the throat of the air flow/mass meter was missing. I exchanged the air flow/mass meter with a used unit from a specialist breaker and it has worked a treat the car runs perfectly. I did not have any error lights on the dash as I had disconnected the battery before fitting.

Coincidentally or not, the cruise control started to sometimes engage and sometimes not. After a few trips of about 10 miles or so it stopped working completely. Then I noticed the speedo sometimes worked and then not. At the same time the fuel gauge showed erratic readings.
Currently the speedo is reading OK, the fuel gauge is not. The computer is giving accurate readings both fuel comsumption and how may miles left in the tank. I am finding this very strange. Incidently the rev counter and temp gauge no problem and no warning lights on the dash.

What I have tried:
I removed and cleaned the lefthand rear ABS sensor, apparently this feeds these two gauges.
The plug to the loom was spotless and the rest did not appear dirty. I blew out the mounting hole with an air line whilst turning the drive shaft, again minimal dust.
A road test did not result in any change.
I then did the same on the righthand. Again no change.
One thing I did not do was change the sensors from left to right. I believe they are the same.

I need help please, any ideas would be greatly appreciated.
Mike Fishwick
Joined: Fri 19 Jun, 2009 10:27
Posts: 2093

  Z3 roadster 2.8
Location: Daglan, France

Re: Cruise control failure, erratic fuel gauge and speedo

Post by Mike Fishwick »

The speedo is not fed by the ABS system, but but its own sensor on the back of the final drive, which I think also provides the input to the cruise control.

My speedo was once rather tempramental, the problem being that the wirng connector was not locking onto its mate on the final drive - I ended up by securing it with small tiewraps, and it has worked fine ever since.
A Z3 is not just for Christmas - it's for life!
User avatar
BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2225

  Z3 roadster 1.9

Re: Cruise control failure, erratic fuel gauge and speedo

Post by BladeRunner919 »

It sounds like a bad connection or bad earth somewhere - you would be very unlucky for three unrelated faults to appear simultaneously (cruise/fuel gauge/speedo).
As Mike said, the abs system has nothing to do with the speedo anyway.
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Cruise control failure, erratic fuel gauge and speedo

Post by Southernboy »

This is the speed sensor on the diff...check the connection there...
Image
"Normal is overrated"
Image

Z3 Upgrades and Additions
dixie4
Joined: Sun 22 Jun, 2014 09:53
Posts: 11

  Z3 roadster 2.2i

Re: Cruise control failure, erratic fuel gauge and speedo

Post by dixie4 »

Thanks to Bladerunner and Southernboy for your help The diff sensor is my next item to check.
It is times like this that I wish I had a pit or a ramp.

Regards,
kkkrisss
Joined: Thu 13 Jan, 2011 09:15
Posts: 189

  Z3 roadster 1.8
Location: Munich

Re: Cruise control failure, erratic fuel gauge and speedo

Post by kkkrisss »

do you have any stored error codes?
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Cruise control failure, erratic fuel gauge and speedo

Post by Southernboy »

You might want to check the brake and clutch switches for their working integrity. As you know they both operate as cut-outs for the cruise control. Also might be wise to check the connection of the brain-box under/behind the glovebox. The speedo may not be associated with the problem and it might be misleading you since both items are behaving erratically. On my 3.0 there are 4 fuses relating to the instrument cluster, and one of them recently malfunctioned on my car with the speedo and and fuel guage not operating. Have a look at the list of related fuses on your car on the underside of the fusebox cover...pull them and check them all. One may simply have a poor connection.
"Normal is overrated"
Image

Z3 Upgrades and Additions
dixie4
Joined: Sun 22 Jun, 2014 09:53
Posts: 11

  Z3 roadster 2.2i

Re: Cruise control failure, erratic fuel gauge and speedo

Post by dixie4 »

kkkrisss wrote:do you have any stored error codes?
Not sure how to find these without visiting a BMW specialist.
Is there a DIY way?
dixie4
Joined: Sun 22 Jun, 2014 09:53
Posts: 11

  Z3 roadster 2.2i

Re: Cruise control failure, erratic fuel gauge and speedo

Post by dixie4 »

Southernboy wrote:You might want to check the brake and clutch switches for their working integrity. As you know they both operate as cut-outs for the cruise control. Also might be wise to check the connection of the brain-box under/behind the glovebox. The speedo may not be associated with the problem and it might be misleading you since both items are behaving erratically. On my 3.0 there are 4 fuses relating to the instrument cluster, and one of them recently malfunctioned on my car with the speedo and and fuel guage not operating. Have a look at the list of related fuses on your car on the underside of the fusebox cover...pull them and check them all. One may simply have a poor connection.
Brake and clutch switches must be OK as the electric roof is working. Checking the fuses is a good idea, I should have done these first.
Thanks for your suggestions.
dixie4
Joined: Sun 22 Jun, 2014 09:53
Posts: 11

  Z3 roadster 2.2i

Re: Cruise control failure, erratic fuel gauge and speedo

Post by dixie4 »

dixie4 wrote:I am a new member and I have searched the old posts but have failed in my quest for someone who may have had similar problems as mine. If I have missed something please would someone please point me in the right direction.

My car is a Z3, 2002, 2.2 with 38k on the clock that I have owned for 9 years and it has only been used in the summer.
It has never let me down in the past except for an irritating flat spot when changing gear. Back in May I decided to investigate this problem.
It turned out to be one of the soldered wires in the throat of the air flow/mass meter was missing. I exchanged the air flow/mass meter with a used unit from a specialist breaker and it has worked a treat the car runs perfectly. I did not have any error lights on the dash as I had disconnected the battery before fitting.

Coincidentally or not, the cruise control started to sometimes engage and sometimes not. After a few trips of about 10 miles or so it stopped working completely. Then I noticed the speedo sometimes worked and then not. At the same time the fuel gauge showed erratic readings.
Currently the speedo is reading OK, the fuel gauge is not. The computer is giving accurate readings both fuel comsumption and how may miles left in the tank. I am finding this very strange. Incidently the rev counter and temp gauge no problem and no warning lights on the dash.

What I have tried:
I removed and cleaned the lefthand rear ABS sensor, apparently this feeds these two gauges.
The plug to the loom was spotless and the rest did not appear dirty. I blew out the mounting hole with an air line whilst turning the drive shaft, again minimal dust.
A road test did not result in any change.
I then did the same on the righthand. Again no change.
One thing I did not do was change the sensors from left to right. I believe they are the same.

I need help please, any ideas would be greatly appreciated.
This last winter has been very wet here in N Wales and I did find some water in the boot getting in though a, now sealed, tiny hole in the hood. Could my problems be pertaining to damp? Although everyting is very dry after the recent warm weather.
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Cruise control failure, erratic fuel gauge and speedo

Post by Southernboy »

Quite possible. It may seem "dry", however any residual moisture plus warm weather will create water vapour which will settle everywhere it gains access to. In essence water vapour is a gas, so nowhere will be impervious. With the motor just ahead of the dash, there is some heat built up under there which will aid in the creation of vapour... once it finds a relatively cool surface it will condense there into a liquid again... and the cooler surfaces will be inside connectors vs the outer surface... vapour condensing will in turn encourage oxidation to metal parts such as electrical contacts and possibly cause loss of / or intermittent contact. Often disconnecting then re-connecting these will restore the circuits, but a can of electrical contact spray in and on connectors is always worth the effort. It cleans and disperses any moisture and also coats the surfaces with a light oily film preventing further oxidation or shorting of any kind. You might think that water in the boot is far removed from the dash area, but in its gaseous form and given any small air movement inside the car, it will move about and could enter the cabin area.
"Normal is overrated"
Image

Z3 Upgrades and Additions
User avatar
Robert T
Site Admin
Joined: Mon 12 Jun, 2006 10:35
Posts: 10170

  Z3 roadster 1.9
Location: Cheshire

Re: Cruise control failure, erratic fuel gauge and speedo

Post by Robert T »

One thing worth noting is that the instrument cluster gauges are purely there for the benefit of the fleshies driving the car - they simply display analogue versions of the digital values that the car measures from the various sensors. I have seen complete instrument failure on mine, whereby all the gauges read zero, yet the car still drives just fine - but it is such an infrequent occurrence that it has so far proved impossible to trace. It could be that a poorly seated connector or a damaged cable is causing the problems. Try putting the odometer into self-test mode and see what readings you get for fuel level and speed - if these are sensible values whilst the gauges are reading erroneously, it points to a problem with the cluster. If these values are erratic, then the problem is with the data being fed into the cluster and is either the sensors/senders themselves or the wiring between them and the cluster.

The odometer self-test mode is documented in the knowledgebase here: http://www.zroadster.net/forum/viewtopi ... 18&t=20201

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
Image
dixie4
Joined: Sun 22 Jun, 2014 09:53
Posts: 11

  Z3 roadster 2.2i

Re: Cruise control failure, erratic fuel gauge and speedo

Post by dixie4 »

A bit of progress.

Today after a good run the Speedo is behaving it's self i.e. working fine and the same with the fuel gauge.

The cruise control is still inoperative.

Thinking along the lines of damp and fuses I found a 30amp fuse which had blown, this I have replaced.
I have no idea what this fuse is for as the diagram on the fuse box lid does not in any way relate to the configuration of fuses fitted and there are no numbers on the fuse box casing so I am at a loss as to it's function it was certainly not the cruise control.

Thanks again to all contributions, very helpful. I can do without the cruise control for now perhaps this will correct i'tself in due course. It may be a damp issue afterall.

Regards,
dixie4
Joined: Sun 22 Jun, 2014 09:53
Posts: 11

  Z3 roadster 2.2i

Re: Cruise control failure, erratic fuel gauge and speedo

Post by dixie4 »

Robert T wrote:One thing worth noting is that the instrument cluster gauges are purely there for the benefit of the fleshies driving the car - they simply display analogue versions of the digital values that the car measures from the various sensors. I have seen complete instrument failure on mine, whereby all the gauges read zero, yet the car still drives just fine - but it is such an infrequent occurrence that it has so far proved impossible to trace. It could be that a poorly seated connector or a damaged cable is causing the problems. Try putting the odometer into self-test mode and see what readings you get for fuel level and speed - if these are sensible values whilst the gauges are reading erroneously, it points to a problem with the cluster. If these values are erratic, then the problem is with the data being fed into the cluster and is either the sensors/senders themselves or the wiring between them and the cluster.

The odometer self-test mode is documented in the knowledgebase here: http://www.zroadster.net/forum/viewtopi ... 18&t=20201

Cheers R.
Thanks for the test sequence no problem found. Speedo and fuel gauge now working fine on the road. Cruise control another matter.

Regards,
bertiejaffa
Joined: Fri 26 Jul, 2013 09:28
Posts: 1733

  M roadster S50
Location: Manchester

Re: Cruise control failure, erratic fuel gauge and speedo

Post by bertiejaffa »

Yours is a later car which has easy cruise control parts (from your fitment point of view anyway) these can be bought cheap on ebay and can be sold for the same price if replacing them doesn't resolve the issue. As for what "factory fitted" parts for cruise you might need to replace someone will be along shortly to advise I am sure
Here come the girls.....
Image
My //M Refurb
My First Zed Journal
User avatar
Southernboy
Joined: Thu 07 Oct, 2010 12:39
Posts: 6436

  Z3 roadster 3.0i
Location: Johannesburg

Re: Cruise control failure, erratic fuel gauge and speedo

Post by Southernboy »

If your car is the "fly by wire" set-up...ie you don't have a bowden cable from the accel pedal to the throttle, then your cruise control will probably be just the stalk switch and an interface cable / harness. If that is the case, then best check the interface cable connections. It is located under the dash on the driver side. Best check the parts list for your car on realoem.com to ascertain the cruise control requirements.
"Normal is overrated"
Image

Z3 Upgrades and Additions
dixie4
Joined: Sun 22 Jun, 2014 09:53
Posts: 11

  Z3 roadster 2.2i

Re: Cruise control failure, erratic fuel gauge and speedo

Post by dixie4 »

Thanks for the suggestion I will check out in the morning now I know what area to look for the cruise control componants.

The fuse I replaced I think was for the cigar lighter. The element is all rusted up.
Not used it for some years.
User avatar
motco
Joined: Tue 18 Aug, 2009 18:12
Posts: 728

  Z3 roadster 2.2i

Re: Cruise control failure, erratic fuel gauge and speedo

Post by motco »

I have a similar car (very late June 2002 build, 2.2i Sport c.40k miles) and a sticky throttle body caused my bad running, failure to go above idle, dashboard full of lights, etc. These symptoms, variously occurring over a couple of years, were cured by fitting a second hand body but most pertinent to your case is the cruise refusing to operate while symptoms showed.
Post Reply