G62 (coolant temp sensor) problem

Phil Rose pjrose at frontiernet.net
Sun Jun 16 19:53:40 EDT 2002

With our newest Audi (tornado), the engine starts quickly when cold
but it becomes progressively harder to start as it warms. It can very
difficult to restart if it's been warmed up and then sits for about
1-2 hrs before a restart. At first I assumed some sort of
injector/fuel-pressure issue, but today I  found another lead;
however I'm not certain if it is relevant to this problem:

(1) I've found that the CC diagnostic channel 6 reads  a constant
"255" (regardless of engine temp), which means an open circuit for
the G62 (coolant temp) sensor. However,

(2) The G62 sensor output (disconnected) is OK--its resistance has an
expected low value (about 350 ohms, meaning high temp) when the
engine is hot, and it then increases to the expected 2800 ohms (+/-)
after the car cools off in garage overnight (65F). The sensor itself
thus seems OK.

So it appears there is a wiring problem--or possibly a need to
replace the CC head unit. But will fixing this G62 issue  improve the
hot starting? I reckon that the ECU needs to know engine temp in
order to to adjust the fuel/air for starting. Does it get this info
from G62? If so, then our defective circuit can mislead the ECU into
"thinking" the coolant is very cold all the time. On most "cold"
starts this is tolerable, but after warmup, the restarts would be be
using a mixture that is too rich. (????) Anyone encounter a G62
problem of this sort? Am I on the right track?


Phil Rose				Rochester, NY USA
'91 200q	(130 Kmiles, Lago blue)
'91 200q   (57 Kmiles, Tornado red)
	mailto:pjrose at frontiernet.net

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