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I recently bought a used 2002 MINI Cooper. I love the car and the way it drives, but an issue has cropped up that seem to be quite serious. I have read similar stories, but hoped someone might be able to help with this specific issue.

Pretty soon after buying the car, the ASC light started to come on intermittently. A diagnostic used ELM 327 and Torque Pro revealed a fault with the camshaft position sensor, which I have now fixed; probably totally unrelated. Shortly after replacing the radiator and renewing the coolant due to a leak, the old battery died so I recharged it fully. The next day, I went for a short drive along some country lanes near my house in the wet. I hit a large puddle quite fast, which sprayed water up a fair way. All seemed well, until I parked at Halfords to get some bits and pieces. When I returned to the car and started it, I got the ABS / ASC and brake warning light trio, which has been present ever since. Tried a couple of different C110 scanners, but none can connect to ABS, despite connecting to other systems ok. Took it in to a local MINI specialist, and they couldn't connect either, so told me they couldn't help. They did confirm that the battery was a dead duck. Today, I replaced the 13 year old battery with a new one, having read that dodgy batteries can cause issues with the ABS etc. Lights are still there though, even after a lengthy drive this evening. Damn it!

I plan to check the ABS sensors (particularly the nearside front which took the brunt of the puddle impact) next. But I figure that the ABS module must be shot if no scanner can communicate with it. I've ordered an INPA scanner, but don't hold out much hope that it will be able to read anything. Can anyone offer any sound advice about next steps? I'm pretty handy, but any procedures I may have to carry out, such as checking wiring looms or replacing the ABS module, are very new and a bit daunting. Should I crack on, or would I be better off just biting the bullet and taking the car to an auto electrician?
 

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As the local MINI 'specialist' got stuck as soon as they couldn't read any codes I wouldn't put much stock in anything they said. Hang on until you get your INPA kit. Once you confirm that you can talk to the other ECUs you might get some direction. You should get a code for no communication with the ABS ECU, so your comments about getting no fault codes make me wonder if they were using a basic scanner that was only showing powertrain codes.
 

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As the local MINI 'specialist' got stuck as soon as they couldn't read any codes I wouldn't put much stock in anything they said. Hang on until you get your INPA kit. Once you confirm that you can talk to the other ECUs you might get some direction. You should get a code for no communication with the ABS ECU, so your comments about getting no fault codes make me wonder if they were using a basic scanner that was only showing powertrain codes.
Thanks for your reply Gary. I have to say they were pretty useless for a supposed specialist. I didn't ask what system they used, probably should've. I'll hang fire till the INPA / ISTA kit arrives, and hope it can shed some light. I think I can manage removing the ABS module, getting it reconditioned if possible, refitting it, and purging the system after. Hopefully a multimeter test of the ABS wheel sensors may throw something up though. Can't wait for the car to be working properly, but it seems like an uphill struggle at the minute!
 

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The ABS module is pretty easy to swap. A little fiddling required to manoeuvre it around the brake lines but nothing horrendous.

If you're testing the sensors with a multimeter it's handy to have a known good for comparison. If your speedo' works then your RH rear sensor is probably fine (as it supplies the speed signal). You can't definitively test them with a multimeter though so I'd wait for the diagnostic kit. It will save you a load of wasted effort in randomly checking likely parts. Also, on an old car like this there's always the chance that when you remove something it'll break.
 

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hall senors ie abs wheel sensors can be tested with a multi meter , ie the hall sensor and the reluctor ring within the hub generate very small AC current and can be measured with a multi meter that has AC setting micro volts setting on it automotive good meter should do it around £30, on each sensor connect the multimeter to the ywo pins at the plug and then rotate the wheel that is off the ground on the car as fat as can and make note of the reading you have , if have all 4 sensors reading voltage then track the wiring back on each one and repeat this at the next plus all way back to abs pump on all 4 corners, this will check the sensor work and the wiring works, if all this does work then most likely ABS pump ECU that is sealed unit part of the abs pump, gen 1 cars have a weak abs pump from new even brand new cars were failing theory is its share part rover part that is in always in the damp part of the car as such,
heads up for diagnostics if ecu has a certain internal fault with its processor no diagnostics eobd diagnostics scanner will detect it,, but a company like BBA REMEN can on a bench test that cost money, what i do is check for live feed to the pump and earth return is present,
its possible to replace the old pump with secondhand one but then its always a risk the replacement might also go same way or already has like some have found,, rule of thumb on this find a unit that came from same year and same spec car, ie cooper s get cooper s one etc, should plug and play
 

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The ABS module is pretty easy to swap. A little fiddling required to manoeuvre it around the brake lines but nothing horrendous.

If you're testing the sensors with a multimeter it's handy to have a known good for comparison. If your speedo' works then your RH rear sensor is probably fine (as it supplies the speed signal). You can't definitively test them with a multimeter though so I'd wait for the diagnostic kit. It will save you a load of wasted effort in randomly checking likely parts. Also, on an old car like this there's always the chance that when you remove something it'll break.
Grateful for your help and advice Gary. I'll hang fire until the INPA kit arrives today or tomorrow. From what I've read, the software assists with purging the brake system once the new module is fitted, is that right? Then, if it's knackered, I guess it will be a choice between getting an ABS module from a scrapped car, or getting the existing one reconditioned. I imagine the former option will be cheaper.
 

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what i do is check for live feed to the pump and earth return is present,
Hi Mike, thanks for your reply and the useful info. I have a good multimeter so all set there. How would I perform the test you describe? Does the unit need to be removed from the car to do it?
 

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Tested the car today with ISTA / INPA kit. Seems the ABS / DSC ECUs are not responding. SO looks like I'm going to need a new ABS module after all! One question; do I have to drain the brake fluid completely to remove the module and pump?
 

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Now you can see there is no response from the ABS ECU my next step would be to check it's power supply and that it is correctly earthed (powers and grounds).

Assuming they are all good I would then ideally check that there is communication/data on the CANbus connector/s but without an oscilloscope you will realistically have to skip this step.

When you know that the ECU has power and the ability to communicate but is still unresponsive is when you should look at replacing it. To answer your other question you don't really need to drain the brake fluid. You won't lose much but have a small tub to hand and some rags to mop up any spills.
 

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Now you can see there is no response from the ABS ECU my next step would be to check it's power supply and that it is correctly earthed (powers and grounds).

Assuming they are all good I would then ideally check that there is communication/data on the CANbus connector/s but without an oscilloscope you will realistically have to skip this step.

When you know that the ECU has power and the ability to communicate but is still unresponsive is when you should look at replacing it. To answer your other question you don't really need to drain the brake fluid. You won't lose much but have a small tub to hand and some rags to mop up any spills.
I have the wiring diagram for the ABS / DSC for the 2004 Cooper. Don't know if it'll be the same, and not sure how to go about conducting the tests you suggest. I think I'll check the wiring loom behind the partition for any physical wear first.
 

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It's really easy, once you've done it you'll wonder why garages haven't learnt how ;)

All you need to do is identify which of the pins are grounds and which supply power. When you've done that you get a test lamp and connect the cable to battery negative (or a shiny bit of metal in the engine bay) and touch the tip to each of the power supply pins in turn. Each should cause the test lamp to light up. Then you connect the cable to battery positive and touch each of the ground pins in turn. Again, each should cause the test lamp to light up.

As long as all your powers and grounds are good the chances are the unit itself is actually broken. If you don't have power or a ground where you should then you're chasing up a broken cable or blown fuse etc.

You could spend ages visually inspecting wiring harnesses but cables can be broken or corroded internally or out of sight so you still don't really know that the cable is good.. A quick check of powers and grounds is definitive and far faster.
 

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You can do the test with a multimeter but it's better with a test lamp. If you have a very poor connection somewhere (imagine a single strand of a wire) then you will get the correct voltage reading. When that strand of cable tries to carry current to a test light it won't manage and your test light will be dim. With a multimeter it will appear that everything is fine though.

You can make a really good test light with a headlamp bulb (in holder) some cable and a crocodile clamp. This is even better than a 'proper' test lamp as it draws more current (~4A vs ~0.25A).

Checking the fuses is good but it's important to make sure the power is making its way all the way to the connector.
 

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You can do the test with a multimeter but it's better with a test lamp. If you have a very poor connection somewhere (imagine a single strand of a wire) then you will get the correct voltage reading. When that strand of cable tries to carry current to a test light it won't manage and your test light will be dim. With a multimeter it will appear that everything is fine though.

You can make a really good test light with a headlamp bulb (in holder) some cable and a crocodile clamp. This is even better than a 'proper' test lamp as it draws more current (~4A vs ~0.25A).

Checking the fuses is good but it's important to make sure the power is making its way all the way to the connector.
That makes sense; I'll purchase a test lamp then and give the diagnostics a shot this weekend. Thanks for all your advice!
 

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Happy to help. Chances are it is the ABS ECU as they are pretty frail. It's always better to test and confirm the fault though, that way you can spend the time to replace parts in the knowledge that you're actually fixing it.
 

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Happy to help. Chances are it is the ABS ECU as they are pretty frail. It's always better to test and confirm the fault though, that way you can spend the time to replace parts in the knowledge that you're actually fixing it.
Yeah, it's good to get to a point where you know the replacement is going to sort it I guess. Process of elimination; quite fun actually!
 

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Happy to help. Chances are it is the ABS ECU as they are pretty frail. It's always better to test and confirm the fault though, that way you can spend the time to replace parts in the knowledge that you're actually fixing it.
Tested the electrics to the ABS module today; all powers and grounds fine, so I've ordered a replacement ABS module from a reputable parts store on eBay. That test light was really useful- much more practical than a multimeter!
 

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A multimeter can do more but most of the time a test lamp is faster and has the advantage of putting some load on the circuit. Hope your ECU sorts it (y)
 

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A multimeter can do more but most of the time a test lamp is faster and has the advantage of putting some load on the circuit. Hope your ECU sorts it (y)
Fitted the ABS module today from reputable parts recycler on eBay. Alas, still got the lights, and ISTA still won't talk to the ABS module. I noticed that, with the ignition on, there is a quiet 'ticking' sound coming from the ABS unit. I hadn't listened to the old one, so don't know if the same was happening with it. Have I been sent a knackered unit? Or is a data connection wiring problem now the only remaining possibility?
 
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