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      09-22-2019, 02:27 AM   #1
doughboy
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Drivetrain error - Aux coolant pump fault

As above i got a drivetrain error and limp mode last week.

Bit of a panic, but then it just cleared after 30 seconds or so.

Ok i thought keep going. Then it came back and went again a few times. This coincided with me having a failed flash on BM3 last week so i assumed these may be linked... Got it home and plugged it in to ISTA and saw 2 faults related to the Auxiliary water pump for charge cooler.

I don't want to take it to BMW or they'll update the car and I'll lose OBD access so i decided to fix it myself.. ISTA gives diagnostic steps and pictures for each fault code so i checked fuses etc jacked the car up and dropped the front undertray to get access to the pump.

Step 1 is check connector and supplies. If that doesn't fix it, it says to replace the pump!

The 3 wire connector was wet and dirty, (it sits right above the front oil cooler rad) checked for supply and ground all good. Cleaned the plug with alcohol, dried it then squeezed it full of silicon grease and plugged it back in.

But i then noticed the short wire loom to the pump was chaffed through the wrap and through the blue wire (LIN bus) insulation and copper was exposed. This was where it rubbed on the top of the ally front subframe squashed by the rest of the main loom tubing.. So as it touched the ally the signal from the pump would be lost. If this happens for more than 30 seconds you get the drivetrain fault.

So... I repaired the wire, taped it up and put sticky foam over the edge of the subframe to cushion the loom.

Fault cleared. Nothing more yet.

This is a common manufacturing defect for sure, something to watch out for if you have aux water pump faults...

Last edited by doughboy; 09-22-2019 at 01:54 PM..
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      09-22-2019, 11:26 AM   #2
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Great post, and well done. Do you have any pics of where the foam went? That might be smart as a preventative measure...
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      09-22-2019, 01:21 PM   #3
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Thanks, I tried to get a photo but it's too hard to see, I could barely get my fingers in to place the foam. See Picture below, the red circle shows foam position.

With the front under tray off if you work back a few inches along the pump wires you won't miss it. On top of the aluminium beam that has the main front control arms attached to it.

There a 1" flexy plastic conduit containing a large wiring loom running left to right on top of the subframe and it has a small plastic opening where the pump wire's tee off, but that is pointed down directly on top of the beam instead of sideways so the pump wires are crushed at 90deg under the weight of the loom conduit.

The pump is item M60535 in this image link, bottom right. You can see the lead going upwards to the loom https://www.newtis.info/tisv2/a/en/f...cou/1VnXu0lnjr

Fault info code 20A203 link https://bmwfault.codes/XMLDiagView?d...MAMgA1ADAANAA=
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Last edited by doughboy; 09-22-2019 at 01:56 PM..
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      09-23-2019, 12:40 AM   #4
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Good job fixing it! Thanks for sharing. One less trip to the dealer the better

My car is showing an oil change is due. Only drive 2k miles since the last oil change. Need to find a dealer that won’t update my dme.
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      05-14-2021, 08:47 AM   #5
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Quote:
Originally Posted by doughboy View Post
As above i got a drivetrain error and limp mode last week.

The 3 wire connector was wet and dirty, (it sits right above the front oil cooler rad) checked for supply and ground all good. Cleaned the plug with alcohol, dried it then squeezed it full of silicon grease and plugged it back in.

But i then noticed the short wire loom to the pump was chaffed through the wrap and through the blue wire (LIN bus) insulation and copper was exposed.
With the front under tray off if you work back a few inches along the pump wires you won't miss it. On top of the aluminium beam that has the main front control arms attached to it.

There a 1" flexy plastic conduit containing a large wiring loom running left to right on top of the subframe and it has a small plastic opening where the pump wire's tee off, but that is pointed down directly on top of the beam instead of sideways so the pump wires are crushed at 90deg under the weight of the loom conduit.
Doughboy, so I removed the bedplate and inspected more closely what you recommended.. The 3 wire connector to the pump was dirty on the exterior, but otherwise functioning good.. I even tested voltage and power was coming through.

So I traced routing the routing of the cables from the 3 wire connector and didn't see any exposed wires.. even opened up wiring looms and didn't see any exposed wiring. I also followed the wiring of the pump wires that run into the small plastic opening but didn't notice anything out of the norm.. The wires were arched, but did not appear to be making contact with the alloy.

I'm trying to narrow down the point of failure you would recommend to inspect for exposed wiring or where to place the foam to prevent the wiring from touching the alloy you mentioned, but I'm getting lost for where specifically to look..
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      05-14-2021, 11:00 AM   #6
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Great write up, I assume if you change the radiators and charge air cooler when you're at stage 1 or above this could also fix the problem?
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      05-17-2021, 02:42 PM   #7
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Quote:
Originally Posted by hlm2c View Post
Doughboy, so I removed the bedplate and inspected more closely what you recommended.. The 3 wire connector to the pump was dirty on the exterior, but otherwise functioning good.. I even tested voltage and power was coming through.

So I traced routing the routing of the cables from the 3 wire connector and didn't see any exposed wires.. even opened up wiring looms and didn't see any exposed wiring. I also followed the wiring of the pump wires that run into the small plastic opening but didn't notice anything out of the norm.. The wires were arched, but did not appear to be making contact with the alloy.

I'm trying to narrow down the point of failure you would recommend to inspect for exposed wiring or where to place the foam to prevent the wiring from touching the alloy you mentioned, but I'm getting lost for where specifically to look..
I can't give you any more ideas really other than the description above.

Unless you have a genuine pump fault perhaps? Do you have ISTA? You can run a pump test with that.
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      05-17-2021, 02:44 PM   #8
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Quote:
Originally Posted by lnsaneM View Post
Great write up, I assume if you change the radiators and charge air cooler when you're at stage 1 or above this could also fix the problem?
You still need the same pumps even if you change the charge cooler.
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