DIY: Replace your Engine Coolant Temperature Sensor (FSI)

Didn't see a writeup around for this, or any big images, so I thought this might be helpful. These steps take place after you have removed your engine cover and/or removed your aftermarket intake. One of the first steps when diagnosing a P2818.

Tools needed:
Flat head screw driver

Parts needed:
Gray Engine Coolant Temperature Sensor
O-Ring
Retaining clip
It would be smart to keep some G12 coolant handy

This part is easiest to replace in the morning, or any time your car is completely cool.



Focus your attention to the area in between your HPFP and battery box.



Locate your ECT sensor on a coolant distribution block, which is mated to the side of the engine block.









Should you unscrew the coolant reservoir?
It's up to you, some people say yes, to relieve pressure. Others say no, keep the vacuum. I say yes. Less coolant will be lost.

The retaining clip faces the side of rear of the engine bay. The easiest way to remove it is to find the clip with your fingers and follow it around the bottom of the coolant distribution block until you reach the end of the clasp. Push the clasp downward and backward, the retaining clip will come free and will be able to be removed by hand.

Have the new ECT sensor ready, with the new O-Ring in place. Coolant will pour out as soon as you remove the sensor.

Two things can happen when you pull the ECT sensor out: The old O-Ring will stay in the block, or come out with the ECT sensor.

If it comes out, quickly swap the new sensor in.
If it stays in, reach in the hole and pull it out. Then put the new ECT sensor in.

The clasp fits back on the coolant distribution block slightly father than the ECT sensor sits in. Check to make sure it is snug.

Use the flat head screwdriver to remove the pigtail harness connector from the old sensor and put it onto the new sensor.

That's it! Start the car and clear your codes.

Nice DIY, haven't had to do this yet, but glad someone wrote it up!

It was definitely easy, the most annoying part about it was finding a thread that depicted where the ECT sensor was actually located :thumbsup:

one or two coolant temp sensors on MKV?

Thanks for the nice DIY!

I recently got a CEL and a scan via VCDS shows error P2181.

I'm going to change the coolant temp sensor(s), first to see if that'll fix it, if not then change the thermostat, if not, waterpump, in that order.

I would like to verify that on a 2006.5 MKV 2.0T FSI, there is only one coolant temp sensor as shown in RobbS's diagram, correct?

There are two of them, actually. This guy is the sender to the dash gauge and is usually the more problematic of the two.

Funny, it appears my other one is taking a dump on me in the colder weather now (that or my thermostat, not sure yet). But your other one is a four wire sensor that sends to the ECU and is located in the thermostat housing.

Would you happen to have the part # for the temp sensor inside the stat?
Or is this sensor a part of the thermostat and is included with a new stat?

Im having trouble starting the car in the cold and someone mentioned this sensor? In the morning around 32 out side it will start then stall out inless u keep it at a constant 2000 on rpm. Whats ur opinion? N no codes ether.

It's easy to replace so I say try it. I found it cheaper through 1stVW parts.

I replaced it the car runs better but now its throwing p0118 any suggestions

Check the connection and the wires. That code is for the value of signal at the sensor.

Was getting the P2181 once every three weeks or so. Now it comes about every other day. Strange is that is appears after 17-18 minutes of highway driving. Not before and not after that time. I replaced the sensor yesterdayand will now try the highway test.

Is there an air bleeding process to get any air caught during the replacement of the sensor ?

This thread is worthless without part numbers.

Also, isn't there more than one coolant temp sensor? i guess there is only one *engine coolant temp sensor, but there are sensors on the inlet and return hoses too. iirc.

fwiw, googling around i found 06A919501A. When i plug that into www.getvwparts.com it comes up 5 times.

Temp sensor 2006-08, RETURN (item 12 on hoses & lines diagram)

Temp sensor 2006-08 (item 8 on radiator & components diagram)

FAN SWITCH GTI (item 9 on cooling fan diagram)

TEMP SENDING UNIT GTI (under chassis electrical / senders / temp senders -- maybe redundant?)

and last but not least:

COOLANT TEMP SENSOR GTI (under "power train control")

I ultimately was able to add the seal and clip to the cart but the godforsaken software that they use (identical to 1stvwparts) does not expose part numbers.

Kudos to VAG for parts reuse? but there are at least three of these, maybe four, under the hood of my GTI. But hopefully only the one of them helps throw P2181.

unfortunately I'm pretty sure my P2181 is caused by a thermostat that is intermittently stuck open.

I have been getting P2181 all the time and the temp gauge was looking fine if not slightly lower than dead center. I changed the #8 part temp sensor when viewing the choices for search of 06A919501A. P2181 was gone for almost a week then returned. I see there is a #12 part listed that says "comes with hose assembly" but not sure what role that would play. I will live with the CEL until the temp gauge really shows a drastic change.

I really don't know much about working with cars, so I called DBC Tuning (Texas) and they gave me an estimate for around $100 including labor. Don't know if that is reasonable.

Debating on not if I should just do the damn work myself. Got some guys who work mostly on Toyota/Lexus to help me out.

SwedishK said:

I really don't know much about working with cars, so I called DBC Tuning (Texas) and they gave me an estimate for around $100 including labor. Don't know if that is reasonable.

Debating on not if I should just do the damn work myself. Got some guys who work mostly on Toyota/Lexus to help me out.

Click to expand...

You should do it yourself. It is way easy. If we're both talking about the one on the driver side of the block, it takes maybe 10 minutes.

Ready the new sensor and oring, remove the intake so you can get to it, push out the old retaining clip, yank out the old sensor, push In the new, insert the retaining clip, unplug cable from old sensor and plug into new, put back in the intake. Done.

You may or may not lose or break the old clip. The old oring may or may not come out with the old sensor.

If you don't lose much coolant you can top up with distilled water in the overflow bottle. If it drops below the min line you should top up with g12 coolant from the dealer or a local import parts shop. You do need g12 coolant - nothing else is truly compatible no matter what they tell you.

Sent by pneumatic tubes