206 1.4 ABS pin out required

[Ric Ochet]

Had an issue with a broken wire to the engine ECU, ran a new power wire to the ECU and got it running again but first drive got an immediate ABS fault. Had the local garage guy put his scanner on it and he was unable to connect to the ABS but could connect to the Engine ECU. This was the direct opposite of the last time he tried (before I replaced the wire) when he could get the ABS but not the engine ECU. Struck me that despite the wiring diagram I'd seen not showing any other connections on that wire it seems likely that there is a feed to the ABS. So I've spliced in the the original red/white (1229 I think was the number) at the BM34 end but have still got the ABS light on. Maybe it just needs a fault code clearing but I'd like to check that power is getting to the ABS so if anyone has a pin out or can tell me which is the feed wire to the ABS I'd be most appreciative. VIN is VF3**************[VIN obfuscated, can be read by forum staff]

[wheeler]

If you cant talk to the ABS unit then I doubt it just needs a fault code clearing.

[Ric Ochet]

I would totally agree, Unfortunately it seems in my attempt to be brief I've not been clear. The local garage guy put his tester on it Sunday and could get no communication. The only thing I've done since he last tried it (at which point the ABS was reachable) is to cut the power feed wire to the engine ECU and splice in a fresh wire. With that in mind is seems likely the wire I cut also feeds the ABS at some point along it's path. So on Monday I opened up the loom again and reconnected the original wire to the new one I've installed and confirmed I'd isolated the free end at the engine ECU. As it stands I have no idea if the ABS is now reachable or not, I don't have ready access to the garage guys Snap-on reader and my own cheap OBD reader doesn't talk to the ABS. So I'm looking to find which pin powers the ABS cpu so I can at least check that it's getting power now. If it is, it might just need a code clearing, if not I've got other problems.

[GiveMeABreak]

This should be the one:



1320 is the engine ECU
7020 is the ABS ECU

BF02 : maxi-fuse output service battery positive
BF03: (No Info)
6739B : Vehicle speed info
MC10D : earth mc10
9009 : K4 stability control / ABS variable damping diagnostic line bus
9001E : Low Intersystem / Can bus
9000E : High Intersystem / Can bus
9001D : Low Intersystem / Can bus
9000D : High Intersystem / Can bus

[Ric Ochet]

Thanks Marc, that's what I was looking for. Although typically I've found that the problem is related to Maxi fuse 3 which has blown. Replaced it only for it to blow again. I'm going to see if there is a direct short to earth but assuming that's not the case any idea on what might be causing it?

[GiveMeABreak]

Here's the details I have on the BM34 unit. Maxi Fuse 3 seems to be exclusively for:

7020: anti-lock brake control unit
or the 7800: ESP ECU (which you don't have, so just ABS).

So I'd be checking the connections on the harness and the earths.

[wheeler]

Does MF3 still blow if the ABS ecu is unplugged?

[Ric Ochet]

Checked for a dead short between MF3 and earth with the rest of the harness unplugged from the BM34 and then again with everything connected and no short detected. Walked away in a huff at that point but thought afterwards that repeating the test with ignition on might be worth doing and I'll also try with abs unplugged. I'll check tomorrow and report back

[Ric Ochet]

Checked with ignition on and again no short and with the ABS unplugged the fuse remains intact so it seems to be a problem with the ABS pump/modulator or ecu. I'm guessing the pump but that's more intuition than anything else. Probably requires another thread but can the brakes be bled following ABS replacement without the use of a diagnostic/service tool to operate the modulator?

[GiveMeABreak]

As far as I'm aware it needs the diagnostic tool to bleed the system after replacement of the hydraulic block.

[Ric Ochet]

I was afraid of that, thanks for your help again Marc.