Polo Engine Management Light

Hi all.

Question for any VW officionados.

My wife's got a 52 plate Polo 1.2. 3 cylinder 65PS version.

She's had some problems with the engine mangement light coming on. The=20 last time it happened was because of a coilpack failure. This time, she=20 called the RAC/AA out first time. They said it was a "Spurious signal=20 from the coolant temperature sensor".

They reset the alarm, but 2 weeks later it's back.

She took it to the local VW Stealer, and they hooked it up to read the=20 fault codes. This time it was...

17511 P1103 035 O2 Sensor Heater Circ. Bank 1 Sensor 1. Performance too=20 low, sporadic

16500 P0116 035 Engine Coolant Temperature Circuit G62 Implausible=20 signal, sporadic.

When the MIL first came on, I guessed it was an O2 sensor problem, and=20 sure enough, there's one up there.

The questions are...

1) Is this a common problem on 1.2 Polos?

2) As an electronic engineer, when 2 sensors come up as "sporadic" and=20 "implausible", I start to think "bad connection, or serious quantities=20 of noise". Would a failing coil pack squirting HT/HV into the ECU cause=20 these problems?

3) If they really *are* the O2 and coolant temperature problems, how=20 hard are they to fit? With 2 hours diagnostics, they said it would be ~ 100 for the coolant sensor. I'm assuming it's a standard "screw into the=20 jacket" job? Similarly, how much would an O2 sensor set us back?

4) Anyone know if these 2 sensors share a multiplug somewhere in the=20 engine bay?

I don't want to take the car to the dealer, have them swap random bits=20 at =A345/hour, for them to say "No idea!"

Any ideas?

Thanks.

Pete.