Intermittent electrical fault?

[keithC70]

My recent purchase is a 2000 C70 T5 Auto and I'm thrilled with it now I have set the tension on the waste gate valve - it was opening at less then 1 psi and the performance was hopeless.

However I now have warning lights appearing. I go over a bump, or sometimes just moving into a parking place on full lock, and I get the two lights 15 Brake circuit failure, and 17 ABS malfunction, then the cruise control stops working, the speedo stops working, then after a while light 21 fault in the engine electronic system, also comes on.

All works fine for a while but the gearbox goes into limp mode with the arrow flashing after the third light.

Fault codes are;

ECM 510F. Speed signal missing,
ECM 530D malfunction indicator lamp TCM faulty signal
TCM 001F vehicle speed sensor signal missing

I delete them and all is well again. Once it stayed ok for over 500 miles but some days it happens several times.

Sometimes if I carry on driving and go over a bump, the first two lights will go out and the speedo starts working again and I can use cruise again if I stop the engine and turn it on again.

Then I discovered that if it happens with the two lights on, and I open the drivers door and slam it, the lights go off and all is well. Then I noticed that if I bang on the dashboard that can also sometimes make the lights go out as well.

So it might be a faulty connection somewhere but I can't find it.

Anyone have any ideas?

Thanks,

Keith

[Luxobarge]

Dry joints on the ABS module - lots on here about this and how to cure it, it's a common fault.

Sounds like the ABS module is losing the signal from the front left ABS sensor, this feeds the speedo and also gives the ECU a vehicle speed signal. If the vehicle speed signal is missing then both the engine and auto box ECUs will get grumpy.

You could just try re-seating the ABS module connector, this is also sometimes the culprit.

[acshortt5]

Might be the electrical part of the ignition switch. Next time the lights appear try moving the key in the ignition a small amount in either direction and see if it cures anything.

[keithC70]

Thanks for that. I'll get the wheel off and have a look when the rain stops.

What's the indicator for the front left Luxobarge?

Cheers,

Keith

[rudi dudi]

No your not getting Luxobarge post properly.
The fault will be in the abs module which is under the pump(a small black box about the size of 2 cigarette packs)
No point removing the wheel for the module.

[Luxobarge]

As above. The ABS module is under the bonnet on the nearside (passenger side) near the bulkhead bolted to the ABS pump - the one with all the brakes lines going into it, you can't miss it.

The ABS module takes the signal from the front left ABS sensor to generate a vehicle speed signal, and passes that on to the engine and gearbox ECUs as well as the speedo.

[keithC70]

Ok, I thought you meant that the speed sensor might be faulty.

I've read up about the abs unit and how to solder the suspect joints so that looks like the next thing to attack.

With no garage though I'll have to wait for a dry spell to take it off.

Thanks for your comments.

Keith

[Bob Meadows]

‘97 V70- Petrol 2.5 Ltr.
Keith: ~ I completed a write up on this last year that may help- but briefly rather than butcher the unit undoing the lid etc. (some have struggled) tap a slim nail into the gaps of the washers holding the lid down- this will snap the same very easily and can be replaced with a star washer.
To remove the lid snap the end of a fine tooth hacksaw blade forming a pointed edge (longer type 12”) wrap a cloth around the holding part or use gloves to protect the hangs.
Work around the box-some will have a groove just below the cover lip- only use the pointed end of the blade as you begin cutting the lid away- only go into the box for approximately 1/8” and you will avoid damaging the internals etc., the glued down lid is quite thin so relatively easy to cut through.
Follow the published method regarding soldering the joints (I soldered the right hand side only- you will identify these from other posts or once the unit is open.
I found that the clear - silicone like substance covering all the solder joints can be peeled back in a sort of blanket form and flipped back once soldered.
Remove the remainder of the cut lip/glue from the main box leaving the groove open to take the sealant for reinstatement. You should end up with a very neat finish to a working module- the connector for the wiring loom has a flip up cover forming a locking mechanism so make sure it seats down properly then flip the lid back over to hold, it should hold tight if you try and pull it off without lifting the cover (clean the terminals etc.)
The warning light will probably stay on for the test but will go out once you do a test drive.

Hope it helps and it should be easier than it actually reads!
Bob.

[DaveNP]

Originally Posted by keithC70

Ok, I thought you meant that the speed sensor might be faulty.

I've read up about the abs unit and how to solder the suspect joints so that looks like the next thing to attack.

With no garage though I'll have to wait for a dry spell to take it off.

Thanks for your comments.

Keith

As a temporary bodge fix you could try wedging the plug for the ABS unit as I put in a pic in Bob's previous thread here (no warranty implied or given but it might help 'til the weather improves)

[keithC70]

Thanks Dave,

Yes I'd seen that and it's the first thing I'll do when I go out this morning.

Keith