Yes Keith, you are right
2 on exhaust manifold, 1 under carpet, just looked at manual :)
according to the manual ;)
heres the figures
@ 20c (68f) all sensors should have a resistance of between 11.7-14.3 ohms
(+B and HT)
if not between them figures replace sensor
Steve,
*edit*
just been out today, had a look, all mine are single wire sensors, so , info not really much use, looks like usa and uk cars have different ones on