Bobby Ricigliano

This will be a new undertaking for me, but it appears I need to replace my Engine Coolant Temperature Sensor (ECT). I have the Bentley and it points out that I am going to have to take off a bit to get to it and the unit itself seems fairly small. I used the VGA to determine the code is 16502 Which means:

P0118
16502
Engine Coolant Temp. Circ.

High Input

I am not sure what the "high input" portion means. Does it mean that the coolant temperature is getting too high or the electrical current to the unit is problematic? At this point I am going to replace the unit regardless but could there be an issue with the wiring leading up to the unit? Also, could this mean that my thermostat is about to go as well? The car has 82k miles on it and I doubt the thermostat has been touched.

The yellow CEL has been on for a few days now but I need to take the car to work and back so this is a situation where I need to take care of the R&R as soon as possible. Anyone with any experience replacing this item on their cars or any other cars? Any insight would be appretiated.

<img src="http://pictureposter.audiworld.com/45287/getimage.jpg">


The posted picture is from the Bentley and the ECT sensor is number 7 in the diagram. The item number 2 (o-ring) also needs to be replaced. Any estimate on parts cost?

Edd W

have been programmed for the widest range of voltages that are possible from the sender, i.e. what it sends for -40c up to 120c. So if the error you are reading is saying the input is too high, then it must be an electrical fault and not an actual fault with the cooling system. So, I would say you are correct in replacing the sender. I have rpelaced several on older Audi's but not on my A6...yet. The hardest part is removing the connector from what I remember. Do it with the engine cold and you need to make sure you do not get an air-lock in the pipe that it is mounted on. To try and prevent this, remove the pressure cap from the expansion bottle and seal the top with plastic sheet, then screw the top back on so it seals really well. Doing this will ensure you only loose a few drops of coolant and do not get an air lock. There may be a bleed valve on the pipe just to make sure after you have fitted the new sender.

Do not forget to remove the plastic seal from the expansion bottle or the system will explode!

In terms of cost, I am not sure for the A6 but for the 100 it was about £110 from the dealer so I bought one from my local brakers yard for a tenner.

QCRAZY

High input indicates that it's sending a high value to the ECU. This could be a high or low temperature depending on how the sender is calibrated (I don't recall off hand).

Most temp senders in Audi go to high resistance for low temperature. When the fail they spike to a high resistance. This one could be the same. What temp does your temp gauge indicate?

Since the car is getting a signal (high input) it's unlikely to be a wiring problem.

The part is somewhat difficult to get to. But it's not that bad. The sender can be had for ~$30 and the o-ring would cost a few bucks from the dealer.

Richard Solomon

AESIS sends you over to a section on checking the ECT which basically has you read measuring block 4 and look at field 3 which is supposed to be the engine coolant temp. They have you do that on a cold (~12 hours off) engine and say it should read roughly ambient temp. If so, start engine and watch temp climb "evenly". If temp doesn't start around ambient and climb evenly, then replace the G62 sensor.

Having done that I'd be pretty confident of the sensor swap, though you're correct it could be wiring...which they cover on the next page...

HTH

QCRAZY

You don't need VAG for that. You could check that on your climate control!

Bobby Ricigliano

There is no rapid spike or an unsteady climb. The car reaches a normal operating temperture after about 5-10 mins of steady driving. I am not sure if the instrument cluster gets it's reading from a differenet guage or not. I have read where people suggest that it may. I have never seen my coolant go above the very center of the gauage and I have never seen my oil temp go above 200 degrees. The car does not seem to be running any different than before the CEL came on. Would you suggest I order the part from Clairparts.com?

Bobby Ricigliano

they refference. The Bentley is a good start for me but I come here for the layman translation. I appretiate your help.

I really hope it is not the wiring. I would not know where to begin to trace the problem from there. The fact that it is a code in the same block as the MAF and other highly problematic areas leads me to believe this is a highly replaced item.

Richard Solomon

Prolly the sensor, but do go through the diag steps in Bentley, assuming they're similar to the ones I posted. You can do that VagCom stuff during the week and bug the forum about your results, then do the real wrenching on the weekend.

Best of luck, I think you'll do fine!

brianmski

I did mine. it is really a pretty easy fix...once you get your hands down to the sensor

QCRAZY

...sensor. It's so cheap and such a common failure part that it won't hurt to replace it. I have a VAG and I still wouldn't bother checking the sender.

You shell out ~$35 and get a new part that is known to fail. More than likely it will fix your problem. If not, you don't have to worry about the sensor for a few years.

The "old" cars used to have two sensors but they did away with one of the sensors. The same sensor does the ECU and the temp gauge now. However, they use different wires for each, IIRC.