17704 - Error in Mapped Cooling System (check Temp-Sensor and Thermostat)

[vtraudt]

Error kept returning.
Replaced coolant temp sensor (rear of cyl head bank 1) with new green (existing was black).
Code did not come back initially, but later returned.
Also observe that coolant temp gauge in cluster was reading low (lower quarter; normal temp is middle)
VAGcom reading of coolant sensor showed also fairly low temps (60 degree even after quite a bit diving).

IIRC, the 'mapped cooling' error is generated when ECU feels that measured temperature is not in line with expectations.

a) what sensor actually drives the cluster gauge?
b) what sensor feeds ECU?

Since the CTS is a 4 pin, I think there are actually 2 measuring circuits in there?

Aside from the coolant temp sensor, is there another sensor that MEASURES coolant temp?
Aside from the CTS, the mechanical thermostat (under timing belt covers) is listed as potential source for "MAP cooling system" code. I assume that a stuck open thermostat may lead to LOWER coolant temps than the ECU would 'expect' and causing the code?

The one in the lower coolant house is only switching the electrical fan on if I am not mistaken.

What additional troubleshooting can be done to determine the cause for the error code?

[Ob3R]

Its most likely thermostat by the timing belt. I have the same code, and the only thing i havent changed out is the thermostat.

Sent from my Forever Check Engine Light B5 S4

[Robsa6]

I've got this code as well and I put a lower temp thermostat in when I did my belt... DO'H