75ZT Community

I wonder if anyone could help, with your inexhaustible resources and knowledge of our cars (I always say a little flattery goes a long way!)

I have a little (?) Problem. Traction Control.....

The Traction Control warning light had come on intermittantly over the past 4-6 months, but a quick turn off and on of the engine reset every thing. I was hoping it was all this damp weather was to blame, although the car is garaged every night.
However now it is permanent!

The symptoms are after turning on the ignition:
1. Traction control warning light comes on within 3 seconds or so of turning on the ignition.

2. After about 20-30 seconds the Rev counter and the temperature gauge cease to work and the gear selected window on the dashboard (IPK (Instrument pack (IPK from the German))?) does not show. The warning light for the rear heated screen also does not light, although there is the tell tale “bleep” when switched on.

3. If quick enough, the take up does engage if the “D” is selected straight away, but soon drops out.

4. There appears to be only one gear operational, in that “slippage” is apparent during a standing (very sluggish) start and no gear change is decernable. Therefore at 50-60 mph the revs sound like they are at 2500 - 3000 RPM. or more. No other gears can be selected apart from Reverse Neutral and Park, when stationary.

5. Gear changes from “D” to “N” "P" and “R” are very severe.

Oh! and the MPG reading before the battery off time was a very optamistic 39mpg+ bearing in mind driving mostly in what what be third gear, but after the battery disconnect will not reset or read anything just "__ ___"

The last two days I have had to run the car in this state until my return last night. As I mentioned above, in the past simply turning off the engine and restarting used to reset to normal driving attitude, but now seems it would appear that the fault is now permanent. As a preliminary I did disconnect the battery, initially for about 20 minutes, then again for about 2.1/2 hours in the hope to “reboot” the system. No change.

Your comments and advice would invaluable. Will I do any permanent damage if I continue to run the car?

Mechanicals I can cope with.... computers/ECU (Engine Control Unit)'s etc., I am lost!
Many thanks
Chuck
The car is a 1999 MK1 2.0L petrol Auto.

As I've said in my PM, it sounds like a CAN (Bus Controller Area Network) bus fault. I didn't see how that would explain the heated rear window, but I do now. The HRW only works when the engine is running and with the CAN bus down, the car wouldn't know.

It's also possibly an engine ECU problem. I assume you have checked your plenums?

Plenums are dry.
So first stop is the CAN bus? is that replaceable/repairable. Something I can do or needs the expertise workings?

I have to go out now so may be delay in replying. I will be here again this evening.

The CAN bus isn't something in its own right. Basically its two wires that link various of the computers in the car together, so they can exchange information. These systems are the Engine ECU, the auto gearbox ECU, the ABS (Antilock Braking System) ECU, Traction control ECU, instrument pack. What usually happens is the wires rub trhough and short to the car body, which means all of those things can't talk to each other anymore. So the traction sulks because it can't get information from the engine and ABS, the gearbox sulks because it can't get information from the engine, the instrument pack can't display information from the engine, like RPM and temperature, nor information from the gearbox like what the gear selector position is.

Basically its a case of checking the pair of wires to see if you can find the problem. Sometimes they break at one particular unit, but usually only that unit goes faulty. This doesn't sound like your problem, because it seems no unit can talk to any other.

The wires in question are a yellow brown and a yellow black. They are twisted together and there is a pair goes to each of the units I mentioned. The most likely place for the problem is under the wheelearch, on the left. You need to remove the liner, or at least peel it back, and have a look where the wiring runs over the wheelarch, and then splits to go into the plenum area (for the engine ECU) and into the car just by the passenger fusebox. There's a sharp edge, that can wear through the wiring and short to ground. You might prove it's there, simply by moving the wiring around a bit, and the problem might go temporarily, proving that's where the problem is.

If it started to happen just a bit and touch for a very short time, it would trigger the traction light which would reset on ignition. However it would continue to wear away, and eventually touch all of the time, meaning none of these things would work.

Another possible check is to look at the voltage on the CAN bus. You could do this by removing the instrument pack, and removing the connector with the yellow black and yellow brown wires. That's the white connector, on the left side as in the vehicle. With the ignition on use a meter to check the voltages. They should both be around 2.5v with ignition on. One (yellow black) will be a bit higher, one a bit lower. If either is down at zero volts, or up near 12v, then it confirms there's a fault, probably on the wiring itself.

A T4 (Testbook version 4.Computer Diagnostic System) would probably help to confirm this, by looking at fault codes in those ECUs affected.

There is still the possibility of a power feed or ground problem, but given the symptoms my hunch would be to check the CAN bus first.

Wow! Duncan, Thorough as usual...
This will keep me busy tomorrow. Today it ran quite well. First start, the TC light came on with the same symptoms as previously described. Stopped after a minute or so; when restarted no light and all operations as normal. The car performed fine and to spec. for the rest of the day.
Then coming home ... TC light on but all operations normal! Does sound like wires touching, doesn't it?

Looks like you're on the right track Duncan. I only had time for a "quick wiggle" today! From the plenum I found the wires that go through to the wing. switched on the ignition - TC light on - had a quck wiggle - TC light out on resetting ignition, very positive (I hope). I will endevour to find time over the next day or so and check the wires under the wing.

Many thanks for that, I will keep you posted.

I hope it is right, sounds good!

I think I may have found some trouble. The plug into the ABS has some corrosion on the plug and socket faces, and the end flat pin finally gave way. Am I on the right track?

Cannot find the CAN BUS wires as a twisted pair though, and all seems well in the wheel arch.

Looks like you have some nasty corrosion going on at the K bus end of the plug, on my diesel traction control plug the K bus wires are at pins 24 and 40 as below , they wont be twisted at the plug but will be back in the loom, hope this helps

I think the big headache now is, how do I repair it? is it possible just to buy the ABS socket on its own? Clearly the Broken pin is not going to be replaced or is it?, mind you, not sure if others are any good...

Should be simple enough to replace the contact assuming one of us has suitable spares. Any chance of a photo of the type of contact please?

I doubt if you could get a plug on its own but plenty of traders now who may be able to supply a good used one if you want to go down that route, but you will still have to transfer all of the wires across and fix any broken ones in the process.

You should be able to remove the wires at the corroded end of the plug , clean it up and fix the broken ones but you need to take advice on how to clean up all the contacts and replace the pins, suggest you respond to Paul who may well have the pins and advice you need

Thanks Rob,
Paul the photos are showing a surface corrosion on the plug (cable end) which seems to clean up OK, but it is the socket on the ABS unit that is worrying. The pins are very delicate probably due to the corrosion. The only one I can see that is terminal is the last one of the flat pins looking right to left that has now failed.

I take the point on a complete ABS unit from a breakers or similar which maybe the quickest and easiest(?) way.
Sorry about picture quality!

I am open to suggestions
Chuck

I would suggest a replacement ABS module, as the pins won't be replaceable. They will be special ones fitted direct to the PCB (Printed Circuit Board). I think Rob means CAN bus rather than K bus. That could easily stop CAN working, but the big pin will be main power or ground. I have heard from insurers, on other makes of car, never on Rovers, that this same water damage was known to cause bigger problems. You also need to stop the water getting in so it doesn't happen again. It's probably been coming up the earth wire by capillary action!

Ah, yes. Now I see the problem.

I think that I'd be changing the ABS unit as you suggest, considering the safety critical nature of the beast.

I was dreading that! Let us hope it is the route cause of the problem.
I see one on eBay at £100 so would that be the going rate?
http://www.ebay.co.uk/itm/190395231508? ... _162wt_952
Or would there be anyone in the club worth trying. I would prefer to support our lads first.

I paid £45 for my T/C unit a few months ago.

That's more like it! Any pointers would be welcomed....

It's just a case of waiting for one to come up on fleabay Chuck. Personally, I'd say that £100 was too much for a second hand one but you know your own budget.

The £100 one looks new, though. The listing doesn't say, maybe he has a mix of new / used.