2015 Audi Q7 TDI Coolant Thermostat Valve

[Smashed Ixnay]

Code P0128 [232] Temperature below Control Range

My wife got a CEL Monday morning, and I diagnosed it with my vcds scanner. She took it to the dealer today and they said it is leaking coolant, needs new thermostat, and isn't covered by warranty. The cost to fix was $1,301.12

After I talked to the mechanic over the phone I told him about my car issues I had with coolant, and wanted to ensure this would fix the issue if we paid it. He said it would. He said basically the thermostat is getting stuck open, and the car could overheat, and take longer to warm up in the mornings. Weird thing is the code was on M-W, but this morning (Thursday) the code was off when she started the car up to drive to Audi. The CEL is still off as of this moment (6pm EST).


I'm finding the fix is possible a $23 part from idparts called the coolant temperature sensor. Is it worth my time to spend $30+-, with shipping, to see if I can find someone else to change the whole engine coolant thermostat kit? Part number is 059115389P from what the mechanic said. It's about $300+-.

If I can't find someone and that is the correct diagnosis, and I can't find someone to do it, then I guess I would have them do it. I just want to make sure the coolant temperature sensor possible couldn't fix it before I possibly splurge a bunch of money at the dealer.

 

[TDIFella]

TTT

 

[Smashed Ixnay]

TTT

So the two+ month update is that the light came on 08/05/2020, and was off the day she took it to the dealer (08/08/2020). I ended up ordering the coolant temperature sensor and planned to swap it out, but the light hasn't come back on. We put on 2k miles over Thanksgiving when we went to NC/TN, and had zero issues. I think in total the vehicle probably has had about 2.5-3k miles since the issue popped up. I figure why mess with it if the vehicle is working fine. We were getting great mpg's, in the high 20's (with rest area stops and idling to eat food), and even for 100 miles I was getting 31.7mpg going 70mph.

IF the light does come back on, I will try the sensor if the CEL doesn't go away after a few days. If that doesn't fix it and the light is still on, then we will have Audi replace the whole engine coolant thermostat kit.

My wife doesn't like the fact that it may cost us $1,300 to fix the issue, but considering we paid $32k for the vehicle 2 years ago and this may be the only real big expensive we've had, then I consider that a deal when new ones go for high 50's, even into the $60k+ range.

 

[Smashed Ixnay]

2015 Audi Q7 TDI burning through coolant. This is kind of a follow up to last November when we had the same issues, but it went away after I filled up the coolant.

About 6-8 weeks ago the CEL came on again. The vehicle was low on coolant. I filled it up and everything was fine again. Today my wife calls me and says her CEL is on again. When she got home tonight I checked her coolant and it was pretty much empty. So in a matter of 6-8 weeks it has a leak or is burning somewhere.

I scanned it with VCDS and the 3 codes are:

4484 - Coolant Thermostat Valve
- P0128 00 (096) Temperature below Control

9567 - NOx Sensor 2 Bank 1
- P20EE 00 (096) Efficiency too low

17277 - SCR NOx Catalyst Bank 1
- P20EE 00 (096) Efficiency too low
- [SCR NOx Catalyst Efficiency Below Threshold Bank 1]


So my question is, would the coolant thermostat valve cause the coolant to leak/burn? What about the NOx sensor or SCR NOx Catalyst Bank 1? I told my wife to take it to Audi to have them warranty those parts and go from there.

In my 2015 Passat TDI I had a long term coolant leak that they couldn't figure out. The dealer insisted I change the coolant thermostat to fix my issues, but the car never threw a code for it. They said they could not guarantee my car would run correctly (no heat issues) if I didn't pay to change it out apart of them finally deciding to change the EGR cooler, dpf, heater core (again, but this time no charge), and a bunch of other sensors. My coolant leaks only stopped after they changed those parts out, and I never had the coolant thermostat replaced. Supposedly the EGR cooler was burning the coolant interally, then throwing debris through the lines, and would clog the heater core immediately.

So my second question is could my wife's car possibly be having the same issue? I have no problem paying Audi $1,300 to have them replace the Coolant Thermostat Valve. I believe it's the oil filter housing part they change out since it's built in. I could be wrong on that. I just want to be sure that'll fix my issue before we pay for it. I may even have Audi do the warranty work, then take it to an independent repair shop if they are much cheaper. the only reason I'd want to take it to Audi is because I know VW would try to void the warranty if they say an outside repair caused the issues.

 

[TurboABA]

Should be covered by dieselgate warranty..... or did you already exhaust it?