Hi, been away for years but would appreciate some help.
Vehicle R172 350. Been plagued with MIL light ON since purchased at 40k miles / 3 years. Set by P2201 code. No adverse drivability. bGood fuel economy.
However after two years or so the code suddenly changes to P0438(12), which is Active (It comes back the moment the ignition is cycled). This code refers to Catalyst Temperature Sensor 1 Short to +ve.
Simple question where is this sensor located?
Access is dreadful without removing the air cleaners etc.
The upstream (closest to manifold) sensor is a 6 wire NOx sensor, with a standard 4 wire O2 sensor after the main cat (022?). There is a temperature sensor T2? after the EGR/O2 injection connection and before a further 6 wire (with it's own module) NOx sensor (023?)
NOx sensors do not have temp sensors within them AFAIK.
Front O2 sensor values OK Likewise Equivalence ratio HC and CO both almost Zero AOK.
Rear Cat S3 different Bank 1 to 2. (Bank 1 OK. Bank 2 Constant 1.72 voltage signal NOK)
Any ideas?