Control Circuit for Coolant Bypass Valve /Open P2681

tony20

Active Member
Apr 19, 2016
48
8
Blackpool
Hi all,

Car - Seat Cupra 280 ST, 65 plate, 50,000 miles.

Yesterday the cars engine management light came on out of the blue, I plugged in the OBII reader and got the error code - P2681 Control Circuit for Coolant Bypass Valve/Open, I've wiped the code a few times and it comes back on right away.

Anyone seen this error before? from looking on the web everything is pointing to needing a new Coolant Thermostat Regulator Housing..

Now i've had nothing but crap experiences with garages, from copper wires put in my coilpacks to divert spark, to screws being drillied into my tyres, trim clips being snapped and the car being ragged around whilst the dashcam is still on.. So I don't trust garages 1 bit.. I actually no longer send my car for services or anywork to garages anything that's doable from home I do myself..

That said, I can't even see this housing regulator looking from the top of the engine bay, I'm guessing it's either underneath or behind the engine? Has anyone replaced one of these and know where it's located / how difficult it is to replace?

I can't say since the warning on the dash coming on that I've noticed anything different with the car, the car is getting upto temp very fast, and taking ages to drop temps when turned off (was it like this before I don't know).. the hoses and random pipes in the engine bay feel hot to touch even just after a few mintues of run time.. I've still got some more testing to do to try figure out exactly what it is.. it could be the radiator,radiator fan, a leak somewhere, but the coolant level hasn't dropped..

I phoned a semi trusted garage, and they have quoted me £800 parts and labour to replace the housing unit.. I really don't want to pull the trigger and pay so much money if it's A. not that, or B. possible to do at home..

Any advice would be appreciated..
 

cupra14

Active Member
Aug 31, 2017
345
65
England
First, I reckon you want that valve to work (not suggesting you don't agree). Second, I think that code could mean a problem with such as a connector or wiring.

Maybe someone else has better ideas...
 

tony20

Active Member
Apr 19, 2016
48
8
Blackpool
I've just been out for a drive in the car, I got it up to temp and I noticed when I got back home the car was very quiet..(normally fans are spooled up wiring) The radiator fans are not working!! They are not spinning at all, I'm now thinking it's a problem with either a fuse / wiring or the fan motor has blown.. which hopefully will be a cheaper fix!!
 

cupra14

Active Member
Aug 31, 2017
345
65
England
Try not to drive till fixed - I don't know how hot some parts may get, possibly causing serious engine damage.
 
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tony20

Active Member
Apr 19, 2016
48
8
Blackpool
Update.. noticed the car starts up from over night cold with the coolant sat at 90degrees nevers goes below or above 90.. from cold start.. after doing some digging, I think it's the coolant temp sensor that has gone faulty so i've just ordered one.. I will fit it tomorrow and hopefully that fixes the issue.. Kinda explains why the fans aren't kicking in but will kick in with the AC on.. car thinks it's at 90 all the time..
 

tony20

Active Member
Apr 19, 2016
48
8
Blackpool
Still having problems with this, changed the coolant temp sensor, paid £800 to replace the thermostat housing and waterpump.. 30 minutes after picking the car up from being repaired.. boom engine management light- P2681.. I'm losing the will to live.
 

DEAN0

Old Git
Feb 1, 2006
5,315
323
Preston - UK
Still having problems with this, changed the coolant temp sensor, paid £800 to replace the thermostat housing and waterpump.. 30 minutes after picking the car up from being repaired.. boom engine management light- P2681.. I'm losing the will to live.
Have a look here - it may help
 
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leonlad

Full Member
Mar 28, 2004
1,130
49
london
Still having problems with this, changed the coolant temp sensor, paid £800 to replace the thermostat housing and waterpump.. 30 minutes after picking the car up from being repaired.. boom engine management light- P2681.. I'm losing the will to live.


i had the same issue but thermostat housing fixed mine, i used a 538036010 from ebay and just paid garage for labour.

you may need the n82 valve as well it shows the same error, or maybe the plug to the thermostat was not cleaned properly when they replaced it as the old one leaks onto it. 4H0121671D is the n82 its at the right side of the engine you will need to take the airbox out to get to it.

it`s a pig of a job to get to the plug for the thermostat underneath i cleaned it with electronic cleaner and fault went away for a few days but came back. i reckon they did not clean it properly or the n82

p28100 is the thermostate housing
p2681 is the n82 valve
 
Last edited:

tony20

Active Member
Apr 19, 2016
48
8
Blackpool
Have a look here - it may help
This fixed the issue thanks Dean0, after changing the thermostat and water pump, I was still getting the error code.. after showing this to the mechanic it's now fixed and the code has gone :) cheers mate
 
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