Fault code help please

I have recently encountered some problems with my girlfriends A2 1.6FSi that I'm hoping someone on here may be able to help me with...

Some time ago (2 months) the engine managment light came on when my girlfriend was driving and this corresponded with a loss of power. She drove someway home and upon examination I suspected an ignition fault, possibly a ingnition coil. Sure enough upon examination of the plugs I found No 2 to be sooty and wet, as opposed to the other three which were OK. I replaced the coil and all is now fine and the light has extinguished itself a couple of days later. I did have a slight concern that the unburnt fuel as a result of the missfire may have damaged the Lambda probe or cat, but all seems well until now.

Bringing you all up to date...

Firstly the engine managment light came on again so i read the fault codes (with VAG-COM) and recieved the following...

VAG-COM Version: Release 409.1-US

Control Module Part Number: 036 906 013 F
Component and/or Version: MED7.5.11 4628
Software Coding: 00051
Work Shop Code: WSC 02138
Additional Info: WAUZZZ8Z33N015908 AUZ7Z0B2206656
2 Fault Found:
17446 - Heating Circuit for Nox Sensor: Open
P1038 - 35-00 - -
17700 This code did not have a description.

The car still runs fine but I plan to investigate this further..

More recently the EPC light illuminated along with the still illuminated engine managment light. There is no accompanying loss of power as stated in the owners manual. Upon reading the fault codes the following code has been added to the above...

16955 Cruise/Brake Switch (A) Circ Malfunction


Firstly, I have read the other thread in the NOx sensor problem and before I start replacing parts I would like to investigate this further. Does anyone have a resistance value for the NOx sensor heater element? If I can check this and it is OK then that takes the sensor out of the problem.

Secondly, does anyone know what the code 17700 indicates (I have searched the web to no avail)?

Finally, Given that the brake lights are working fine, does anyone have any theories on the brake circuit fault?

If anyone can offer any ideas I would greatly appreciate it.

Thanks for looking and sorry for being so long winded.



Well-Known Member
Hi Steve,

Not too sure about the 17700 code, possibly a coolant temperature sender problem, but not 100% on that.

As to the brake/cruise code, here is the word, from Audi:

16955/P0411/001393 - Brake Switch (F): Implausible Signal

Possible Symptoms

* MIL burning
* No Brake Lights

Possible Causes

* Wiring and/or connections faulty
* Fuse defective
* Wrong brake light present (21W in stead of 5/21W)
* Brake Light(s) defective
* Brake Switch (F) defective

Possible Solutions

* Check wiring and/or connections
* Check / Replace Fuse
* Check / Replace Brake Lights
* Check / Replace Brake Switch (F)

Special Notes

* In Europe at VW-cars the Brake Switch (F) had the bad reputation of breaking down often

Hope that is of some use to you!




Well-Known Member
Hi Steve
Not much help - but I tried the Gendan web site which has a fault code data bank (access requires free registration) but it did not list anything for 17700

Cheers Spike
Hi Steve
engine coolant thermostat open circuit
probable cause
wiring open circuit/ engine coolant thermostat
thats what auto data says for 17700
hope this helps


Brilliant respose guys, thanks.

I will be ordering a brake light switch as the brake lights work fine.

Where is the location of the engine coolant thermostat, is it on the thermostat housing?

Thanks again

OK, had a quick look at the NOx heater element open circuit problem.

RE diagram below..

I am getting battery voltage (engine running 14.4V) on pin 10 of connector T10 to earth but only 11.6v across pins 8&10 of the same connector.

Does anyone have further diagrams of where the pin 8 of T10 goes to earth?

I am getting the same 11.6v on pin 13 of connector T14 to earth but cannot determine which is the -ve terminal of the heater element.

Does anyone have any further diagramd of the pinouts on the NOx sesor?

Thanks in advance


After studying thge current flow diagrams in the service manual (Kindly provided by Skipton01, Thank you) The heater element power supply is earthed through the control module. The control module usses a PID circuit to adjust the current to to heater element to maintain the correct tempreture, hence the 11.6V. After checking the sensor heater element I discovered the resistance was in the Mohms, which is not what I would expect for a heater element. I will be ordering a new sensor this week and will post up the results.

Thanks to all for your help.


Fitted a nex NOx sensor last night and this has cleared fault code 17446.

Fitted a new brake light switch, but fault code 16955 soo returned. Have since cleaned the bulbs (quite dirty) and the bulb holder connectors and cleared the fault codes. It's still clear after a run around the block so we will see.

Could this implausable signal on te brake light switch have anything to do with heel/toe downshifts. I.E the ECU is seeing throttle and brake at the same time?

The EPC light is back on. The bulbs are the correct twin filament 21/5w and the switch is new! Going to have a look at the earths next.

Thanks for the link.