Bad coolant temp sens

DDress · 03-18-2021, 11:32 PM

Hey guys just wondering if it's possible for a bad coolant temp sensor to cause the car to run to cold/possible make the thermostat not operate properly. My car has been running pretty cold and has the code P0128. I literally just replaced the water pump and thermostat drove it about 10 miles and got that code. So I'm thinking it's a bad sensor somewhere. After about 10 min in the car the check engine light comes on and the fan starts running at a super high speed. Either I got a bad thermostat, it's something with the wiring, or I'm hoping it's just the coolant sensor. Anyone else have this issue?

dtla1 · 03-19-2021, 11:07 AM

Might seem like a weird question, but did you run the bleeding sequence?

MightyMouseTech · 03-19-2021, 01:58 PM

First off, get something you can read real BMW codes, not generic OBD codes.

Is your car an automatic? Could be a stuck open thermostat in the trans cooler.

DDress · 03-19-2021, 03:29 PM

Quote:

Originally Posted by MightyMouseTech

First off, get something you can read real BMW codes, not generic OBD codes.

Is your car an automatic? Could be a stuck open thermostat in the trans cooler.

I'm reading the code from a Cobb access port. The code says "coolant thermostat(coolant temp below thermostat regulating temperature) and no it's a standard.

DDress · 03-19-2021, 03:31 PM

Quote:

Originally Posted by dtla1

Might seem like a weird question, but did you run the bleeding sequence?

The guy the did the work said he did. You think I should try and re do it? I was thinking about taking the cap off the coolant res and letting the car run to see if it maybe burps out an air bubble. I just haven't gotten around to it yet.

dtla1 · 03-19-2021, 03:49 PM

Quote:

Originally Posted by DDress

The guy the did the work said he did. You think I should try and re do it? I was thinking about taking the cap off the coolant res and letting the car run to see if it maybe burps out an air bubble. I just haven't gotten around to it yet.

There's an automated bleeding system/option on the car, just need to adjust some stuff to the right settings. Check out this thread, near the picture of the reservoir is where they start to describe how to activate the bleeding procedure:
https://www.1addicts.com/forums/showthread.php?t=995387

03-18-2021, 11:32 PM	#1
DDress New Member 0 Rep 11 Posts Drives: 135i Join Date: Feb 2021 Location: New York iTrader: (0)	Bad coolant temp sens Hey guys just wondering if it's possible for a bad coolant temp sensor to cause the car to run to cold/possible make the thermostat not operate properly. My car has been running pretty cold and has the code P0128. I literally just replaced the water pump and thermostat drove it about 10 miles and got that code. So I'm thinking it's a bad sensor somewhere. After about 10 min in the car the check engine light comes on and the fan starts running at a super high speed. Either I got a bad thermostat, it's something with the wiring, or I'm hoping it's just the coolant sensor. Anyone else have this issue?
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03-19-2021, 11:07 AM	#2
dtla1 Colonel 828 Rep 2,232 Posts Drives: 2011 135i, Space Grey Join Date: Apr 2014 Location: Silicon Valley iTrader: (2)	Might seem like a weird question, but did you run the bleeding sequence?
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03-19-2021, 01:58 PM	#3
MightyMouseTech Major General 4338 Rep 6,196 Posts Drives: 13 135i 6MT LeMans Blue MSport Join Date: Feb 2013 Location: Ottawa, Canada iTrader: (0)	First off, get something you can read real BMW codes, not generic OBD codes. Is your car an automatic? Could be a stuck open thermostat in the trans cooler.
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