EPC light

[S4driver]

After a month of ownership i guess my honeymoon period is over.......

I had a diagnostic run on the car a week or so ago,and it recorded 2 faults; an exhaust temperature sender(sensor?), and a sporadic fault fault for the/a throttle angle sensor. I had the exhaust temperature sender/sensor changed, run the check again and no faults were stored......

However, i was out for a fairly long drive, 150'ish miles. When i started the car again after stopping for about half hour, after a couple of minutes driving the EPC light decided to come on When i got home the car sat on the drive all night, however the next morning, the light did not come on at all

The next time i use the car on a reasonable run was Sunday. The light came on again. After leaving it for a few hours again, i started the car and the EPC light was not on , and has not been on since....

I should be getting the diagnostic plugged in again tomorrow to find out if any other faults are now stored, but would anyone have any idea what could be causing this EPC light to come on? Could it be temperature related, as the 2 times it had come on the car had been on a decnt run - BTW, the temp gauge only ever goes to 90, and the oil temp to 2 notches from cold (100?)

I shall post the fault codes when tomorrow ,hopefully, but is there any pointers in the meantime..........?

[tartan_rob]

Your throttle sensor is on its way out. It is costly to replace. Approx £440 for parts alone. I got one from a scrapped car (1year old) for £120 and changed it in about 20 mins + some throttle body adaptation from VAG-com. The only way to avoid it is to be constantly altering throttle angle....but it will go in the end and make the car undriveable....perhaps speak to VAGParts...? Adaptation does not have to be done as the car does it automatically if your switch her on and leave her for 6 seconds without doing anything.

[Nige_RS4]

Adaptation does not have to be done as the car does it automatically if your switch her on and leave her for 6 seconds without doing anything.

An official audi technical manual states 23 minutes for automatic adaption (this seems kinda long to me).

Nige.

[S4driver]

Your throttle sensor is on its way out. It is costly to replace. Approx £440 for parts alone. I got one from a scrapped car (1year old) for £120 and changed it in about 20 mins + some throttle body adaptation from VAG-com. The only way to avoid it is to be constantly altering throttle angle...............

I take it that this would cause the EPC light to come on then? Does it affect it that much that it limits the power, as that is what EPC stands for, electronic power control...?

[tartan_rob]

23 mins to do an adaptation is too long, even using VAGcom, it only takes around 10 secs.

EPC does stand for Electronic Power Control, but not in manner you are thinking. It simply refers to any monitored component that affects how the engine operates. I did not notice a loss of power but when cruising the car would just die and come back to idle, the throttle sensor had detected a loss of signal (break down of one of the two variable resistors that is causing the fault you are seeing) and the ECU stops throttle activity and you get into the situation you are in....Stopping the car for a few seconds resets the sensor fault.

[Verruckt]

Many problems can trigger an EPC light, it's not exclusive to the DBC components. For me, the dealer had incorrectly coded my instrument cluster and I had constant EPC lights. It had no effect on performance.

Get the EGT sensor replaced because a bad sensor will make your car run excessively rich and lose power.

[tartan_rob]

Verruckt - check the first para on the opening post...

[S4driver]

I had the fault codes pulled from the ECU this morning.It came back with only the following;

17579 Angle Sensor 2 for throttle valve drive. Implausible signal - sporadic.

As TartanRob suggested, this is waht is causing my light to come on intermittently.This being the case, is it the throttle angle sensor i am looking to change? Am i right in thinking that this come as one piece attached to the throttle body(?)?

[tartan_rob]

Yep, correct, that why it is so expensive. The are two sensors, one works from 0-->100% and the other works from 100-->0%. The ECU uses both readings to work out the mean value. Both sensors are built into the complete housing so the whole thing has to be changed.
Sorry its not good news....having said that it may last for weeks or months if you can change your driving style.

[tartan_rob]

Yep, correct, that why it is so expensive. The are two sensors, one works from 0-->100% and the other works from 100-->0%. The ECU uses both readings to work out the mean value. Both sensors are built into the complete housing so the whole thing has to be changed.
Sorry its not good news....having said that it may last for weeks or months if you can change your driving style.

[S4driver]

Cheers