Auxiliary coolant pump / coolant pump B open circuit

[ahsanx]

Hi all, wondering if someone has had a similar issue, searched through the posts but all seem to be solved after replacing the pump.

I have a 2012 Audi A4 B8.5. 2.0d CJCB engine. Eml light is now permanently on for coolant Pump B open circuit. Upon investigation I've found the connection to the pump depinned itself and connector corroded. Had an electrician replace the wiring and connection then tried again but issue still persists. Now, replaced the pump with another unit and replaced coolant. Fault still shows up and after clearing it comes back up after 2 engine restarts.

Engine bay, boot and LH/RH dash fuses all fine. Am I missing something here, is there any fuses anywhere else? If I disconnect the pump the fault appears under engine and aircon but when connected only appears under engine so the connection should be good.

I've contacted the dealership and checked the gov.uk website but my vehicle doesn't seem to be on the recall list even though this issue has occurred. Any suggestions would be appreciated, thanks in advance.

Naz

[VAG-Abound]

What fault code are you seeing, and read with what (VCDS, etc)?

Can you see the (original) colours on the wires for each position in the plug and socket? 1, 2, etc is usually embossed into the moulding on each side of the join. That might help check things are connected as intended.

Does the wire repair look good? For example using pre-made VAG repair wire that fits the housing and other side of connection well? Were both sides repaired, and if not could there be corrosion in one side preventing contact?

[ahsanx]

Hi VAG-abound

Fault code =

System description: R4 2.0l TDI
Software number: 03L906018JP
Software version: 9977
Hardware number: 03L906018JL
Hardware version: H25
ODX name: EV_ECM20TDI01103L906018JP
ODX version: 003006
Faults:
P261A00 - Coolant Pump "B" Control Circuit/Open
static

The repair was carried out by an auto electrician and looks pretty solid. I've checked for continuity through the connector and the lowest point of repair as I'd asked to have the heat shrink left loose until the fault was fixed. I've triple checked all the colours with the original and had a third opinion on it also aswell as going back to the auto elec to clear doubt. All colours match up and the connector is brand new with the wires pre pinned and on the pump end there's no corrosion on the old or the replacement pump. I fear I may have eneded up with another faulty replacement perhaps.

[Crasher]

Non genuine aftermarket pumps often cause this code to keep coming back.

[ahsanx]

Hi Crasher that's what I initially thought hence I got a used "tested and working geniune" part. Well oddly enough I took a little 15 mile odd trip this morning and when I got home, locked the car and went to go inside and I hear the fan going off. Popped the bonnet and sure enough the fans running. So I have no idea where to go from here. Any suggestions would be great as for me that's confirmed that the pump is working. Just need that EML light off.

[Crasher]

Personally I would not trust anything but a new off the shelf pump from TPS, mainly because this is cheaper than checking for a rare wiring or ECU fault. Of course DIY you are not paying £75 an hour labour for checking the wiring so on my own car, that is what I would do.

[ahsanx]

I did actually order a new one the day I replaced it so will see how that fairs when fitted.

[ahsanx]

So bit of an update. The part I initially changed was the auxiliary coolant pump located at the back of the engine by the secondary bulkhead. The pin was out and connector corroded so was definitely a fault there. Part number 06H 121 601 J.

Now, I've had a couple of spare hours today and removed the plenum under there I've found another pump part number 4H0 121 671 B which comes up as a coolant control valve. I disconnected this and ran a scan and no additional faults appeared apart from the same coolant pump b open circuit and fault. Which leads me to think this maybe faulty otherwise another fault would have been picked up.

Question to those that may know is it worth also changing this?

[Crasher]

What is the VIN?

[ahsanx]

VIN is WAUZZZ8K0DA084499