Rear wheels locking

[mmc757]

Yeah, I didnt read closely enough, thats why I deleted my post.
First check is always power for electronic devices. You checked fuses but did you check to confirm the thing is actually getting power?

 

[Wild E. Coyote]

Don't hold me for this, but there may actually be an ABS actuation test burried somewhere in Forscan... That should replicate the self test of ABS module it is suposed to do after startup of the car first time it reaches 20 kph...

 

[grogee]

If anyone knows where this is in Forscan please let me know! Played around with it last night but couldn't see anything relating to ABS

 

[Wild E. Coyote]

Try those diagnostic tests KOEON (key on engine on) and KOEOFF (Key on, engine off). I think they should contain ABS modul test as well.

 

[grogee]

thanks, I'll give it a try.

 

[grogee]

Ok I've tried the following:

1) Plugged in substitute module instead. Turned key on, still no ABS lights.
2) Ran keyon and keyoff tests. No indication of any ABS test in either of these.
3) Tested connector to ABS module. There are 4 'big' pins. 3 of these seem to be battery voltage and one seems to be ignition on. I only managed to find one earth pin in the connector; does it earth through the body? Seems unlikely because it's mounted on rubber.

I'm all out of ideas now. My problem is compounded by the fact that I'm not getting any feedback from the instrument panel / abs lights. So I don't know if I have one problem or several.

Short of any more suggestions, I'm going to take it to an abs specialist and see what they can tell me.

 

[Wild E. Coyote]

https://www.projectpuma.com/viewtopic.php?f=20&t=27154&p=332964&hilit=ABS+pinout#p332964

Here is the pinout for the ABS unit to check it yourself...

 

[grogee]

That's very useful. Thank you. Maybe I am one step closer, because none of the 'big' pins tested as a ground, whereas that pinout suggests 2 of them are, which is what I'd expect. From memory 3 of them were battery and one was ignition live. If it was a bad earth I wouldn't expect 12v on a ground pin??? More fiddling tomorrow I think.

 

[grogee]

So I decided to test instrument cluster bulbs (why didn't I think of this before removing the whole unit???). And the ABS and traction bulbs (LEDs) aren't working. So now I know the ABS might be trying to throw a signal but the instruments can't display it. So now I'm going to try and find an instrument cluster and that will bring the complication of mileage reading... I'm guessing the cluster stores the mileage and not the GEM?

 

[grogee]

Pic

 

[Wild E. Coyote]

Yes, as far as I know, the mileage is stored in the instrument cluster.

Ok, getting there. There is dedicated pin for the light on instrment cluster, have you tried hooking it to a different light? The first thing that comes to mind is the low brake fluid/hand brake on light as the connector is there on the brake fluid bottle. Take a look at my JASAPP thread, there is definition of pins (3) for the low brake fluid notificiation light and connect that to the pin on ABS module. If it lights up, you will know it is trying to send the malfunction signal. Hell, you could test it with multimeter alone for that matter. It is straightforward, I would expect it light up the indicator directly, as everything else on puma is done

 

[grogee]

Yes I was going to try probing the warning lamp pin on the connector with +12v. No. 16, "dash lamps".

Do we think it's 12v or 5v?

 

[grogee]

Another thought - surely the ABS LED on the instrument cluster HAS to be broken because on the instrument LED self test, the instrument cluster controller would simply command 'all lights on'? So as long as the cluster has power, it should light the LED, unless the LED is broken.

So I'm not suspecting the connection to the instrument cluster is faulty/broken.

Thanks for your tip, I'll check out your thread.

 

[Wild E. Coyote]

Yes I was going to try probing the warning lamp pin on the connector with +12v. No. 16, "dash lamps".

Do we think it's 12v or 5v?

Have no idea, TBH! Ford lots of things does his own way. For instance: the vehicle speed sensor signal. Almost everybody is using 5V square signals of various frequency. Asians all use 4000 ppm 5V signal. Ford: 8000 ppm 11V....

But no need for probing light, just use a multimeter. Even those from Lidl for peanuts money will be more than up to the job...
If that is not possible, start with 12V just to be safe. If it works, nice, if not, it is 5V...

 

[grogee]

Now fixed. I'm an idiot. Pulled out the ABS connector and tested the connections. No earth so I traced the wires back to...

...2 black and yellow wires terminating in ring terminals which were flapping around next to the negative terminal of the battery!

Basically during some earlier work that I was doing before I garaged the car for winter, I'd taken battery out and forgot to refit the earth terminals for the ABS.

In my defence they were hidden behind my strut brace, and I had no warning lights on the dash to tell me there was a problem.

Anyway for anyone having a problem in the future, here's what I've learned:

1) check the simple things first!
2) ABS doesn't communicate with scan tool if there's no earth
3) you can remove the connector without disturbing anything else. Use a long screwdriver to pull the top of the connector upwards. This pulls the locking sleeve up and the connector slides off the unit.
4) check the connector pin out in this thread if you're still having problems. The two big terminals on the end are fed separately by 2 x 30A Fuses in the underbonnet fuse box. They are permanently live (not switched).
5) you can test your ABS sensors without jacking car up, at least the resistance value. Use a multimeter in ohm setting and check the pairs which should be 1000-1100 ohms.

More later as I remember it... Basically to test it I just went for a run round the block and stood on the brakes - slight vibration in the pedal and the rears aren't locking any more!

Thanks for all your help guys.

 

[red]

glad you got to the bottom of it! Thanks for reporting back.

 

[Wild E. Coyote]

Thanks for all your help guys.

No problem, glad you sorted it out! And you learned something in the process. I call that success! :wink:

 

[mad4jags]

Indeed,the best lessons learned are usually via mistakes. :grin: