dparnas

I've been getting the following intermittent error codes, which set off the MIL light. They don't come at the same time, they seem to alternate, each coming after driving the car 2 or 3 times. Anyone else experience this?

1. 16502 - Engine Coolant Temp Sensor (G62) Signal Too High 35-10 Intermittent

2. 17704 - Error in mapped cooling system (usually temp sensor or thermostat) 35-10 intermittent

They seemed to begin at the same time as my installation of the G2 supercharger, but don't know why that would have anything to do with the coolant temp. sensor. The car has been running fine and the temp gauge on the dash has not had any unusual readings. If you've had any experience with this, any advice on what I should do would be appreciated. If all I need to do is replace the temp sensor, great, that would probably be the best answer.

hurricanesteve

lots of people have them go bad.

And the dash indicator is pretty much a "dummy light" It will stand straight up for about a 15 degC range...useless for diagnosis.

A better test is the VAG-COM coolant sensor reading. If you can, log it. There is a test you can do with a multimeter in the Bentley if you like.

The sensor is cheap and it's probably worth it to just replace it now though.

dparnas

Easy to do myself? Where would I find the sensor? I've got a Bentley on order, but it will be a while.

Perpetual Novice

the climate control "Backdoor" (See the tech section)to read the actual coolant temp

jason in toronto

i had to replace mine. didn't do it myself but looked easy enough - drained some fluid on the ground

hurricanesteve

that would just tell you if your ECT is good or not...if VAG matches the climate control (sensor IN the radiator), then you know you're probably getting good ECT #'s.

Since he's setting codes, there is a high probability his ECT is bad.

Bert

<center><img src="http://pictureposter.audiworld.com/272/ect.jpg"></center><p>To replace the sensor itself, is a 1 minute job. Getting access so that you can remove the clip to R/R the sensor is another story. Unless you have small hands (the sensor is right under the air intake horn, that's attached to the flex hose that's attached to the MAS), you'll have to take off the intake. That is the PITA part about it. The intake horn is held in place by a 5mm hex bolt that is not so easy to get at. After having said all that, your setup with the G2 may make things easier or harder. Look for a sensor that has 4 wires that goes into a solid water pipe. Mine was blue in color. (P/N 078-919-501B) Also, replace the O-ring (P/N N-903-168-02).

Can you guess from the pic, which one is the new one? ...... I knew you could.

HTH,
Bert

dparnas

OK, so, without actually going in and removing my old one, how would I know whether I have the blue unit or the green one? What year/model is your car? Mine is a 2000 A4 2.8Q. I guess there are two different ones. Also, why are some people saying it is located at the back of the head at the top and you are saying it is under the air intake horn. Is that the same place? I guess I always thought the back of the head was at the back of the engine bay, towards the windshield.

Bert

OK, I just look at the ETKA for 2k, there is two types of this sensor mentioned for your year. xxx-501B (the Blue one) and xxx-501C a black colored one, no mention of green. You'll have to take a quick glance at your sensor to determine which is the right one for you.

As far as where the sensor is... its near the firewall, under the air intake horn that is attached to the throttle body. It is between the firewall and the cylinder head, so yes, same place.

HTH,
Bert

jason in toronto

my 98.5 was blue. i have an extra green one i bought by accident