Fault Code Help

[DeutscheB6]

So have had my 02 A4 Avant w/ 2.0 engine about a week. It threw two codes

16500 Coolant Temp Sensor
17545 Fuel Bank 1 too rich

These codes popped up the day after I bought it and had them cleared to see.

So Coolant Temp Sensor is an easy replace, but the temp seems to go up and down on the highway and never breaks dead center in town. Is it something else?

Fuel to rich could be a myriad of things:
Mass Air Flow (MAF) Sensor faulty
Fuel Pressure Regulator faulty
Fuel Injector(s) faulty
Oxygen Sensor Control faulty
Oxygen Sensor(s) faulty
Evaporative Emission (EVAP) System faulty

But the day I bought it while changing brakes the previous owner was raving about Lucas fuel additive in his BMW. So I threw a bottle in. Could this have caused this code to throw? He stated neither code had popped up during his ownership.

I'm the 3rd owner and she has about 96k on her.

Thanks in advance.

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[16vCorey]

If the coolant temp sensor is bad or reading low it will cause the computer to think the engine is cold and dump more fuel. Fix that and I bet both of your codes go away.

The CTS is different from the coolant temperature sending unit, which is what sends the signal to the gauge. If your temp seems to fluctuate a lot, you probably have a bad thermostat too.

[DeutscheB6]

This is the CTS for the fault code 16500 correct?


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[KHARDa4]

I believe that is the 2 pin for the cluster gauge. The 4 pin sits in the thermostat housing under the intake mani. This is the sensor to help calculate A/F.

[old guy]

I believe that is the 2 pin for the cluster gauge. The 4 pin sits in the thermostat housing under the intake mani. This is the sensor to help calculate A/F.

The 2.0 is a normally aspirated engine only available in Europe so the sensors may be set up a little different. The 1.8T engine has the green CTS located in the rear coolant flange It is a four pin sensor. It sends one signal to the instrument cluster and another signal to the ECM for fueling control.

The thermostat housing contains a heating element that gives then ECM some control over the thermostat. That would be the plug that connects to the thermostat housing. It has nothing to do with the fueling.

If your cooling temperature is going up and down it may be the thermostat. You can data log and confirm or you can replace the inexpensive green CTS and see if it cures the problem. If not, it's probably the thermostat.

[DeutscheB6]

Thanks for the help guys.

That green sensor sits dead center behind my engine and in front of the firewall. If that is the sensor I should be looking at and changing. Is there another area to look on the 2.0?

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[DeutscheB6]

So I have the green 4pin that sits dead center behind the engine and in front of the firewall. I also have a black 2 pin that is in the the lower hose of the radiator.

So on the 2.0 is the 2 pin or green 4pin the CTS. I pretty sure it's the 2 pin but want to verify.

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[DeutscheB6]

So I bit the bullet and went to the dealership. Yeah I know not a wise financial choice, but I did get the right sensor. (Green 4 pin) And it was the only place I could find the dang rear wiper.

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[KHARDa4]

The 2.0 is a normally aspirated engine only available in Europe so the sensors may be set up a little different. The 1.8T engine has the green CTS located in the rear coolant flange It is a four pin sensor. It sends one signal to the instrument cluster and another signal to the ECM for fueling control.

The thermostat housing contains a heating element that gives then ECM some control over the thermostat. That would be the plug that connects to the thermostat housing. It has nothing to do with the fueling.

If your cooling temperature is going up and down it may be the thermostat. You can data log and confirm or you can replace the inexpensive green CTS and see if it cures the problem. If not, it's probably the thermostat.

Oh I automatically assumed that it was a stroker setup lol. I didn't realize there was n/a 2.0 in the b6 besides the v6. Just to clarify what is the blue sensor in the thermostat housing, to monitor cooling performance? Talking 1.8 now.

[old guy]

So I have the green 4pin that sits dead center behind the engine and in front of the firewall. I also have a black 2 pin that is in the the lower hose of the radiator.

So on the 2.0 is the 2 pin or green 4pin the CTS. I pretty sure it's the 2 pin but want to verify.

Actually they are both Coolant Temperature Sensors. They are part of the electronically mapped cooling system that controls the block temperatures based upon the prevailing conditions.

Just to clarify what is the blue sensor in the thermostat housing, to monitor cooling performance? Talking 1.8 now.

The blue plug on the thermostat is actually a heating element that the ECM utilizes to force the thermostat to open under certain conditions. Here is a tutorial for how the Electronically Mapped Cooling System operates. It is written for a 1.6L VW engine but the actual function is identical to that in all of the Audi/VW mapped systems. It's worth the 15 minutes it takes to read through it to better understand how your cooling system functions. Clicky click®

[DeutscheB6]

Well hopefully the green 4 pin is the answer! I'll find out tomorrow

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