Subaru wrx, eml light came on

markmcp · 11-03-2015 11:56pm #1

Hiya people,

Just wanted to get some advise, was cruising along this evening at about 50 mph engine light came on.. done a diagnostic error p0420 catalyst system efficiency below threshhold bank 1 googled it, and it seems that the rear o2 sensor maybe at fault, im hoping its not the cat, has anybody had the same issue and can confirm it is the sensor for sure any help is much appreciated....

dieselbug · 12-03-2015 10:45am

markmcp wrote: »

Hiya people,

Just wanted to get some advise, was cruising along this evening at about 50 mph engine light came on.. done a diagnostic error p0420 catalyst system efficiency below threshhold bank 1 googled it, and it seems that the rear o2 sensor maybe at fault, im hoping its not the cat, has anybody had the same issue and can confirm it is the sensor for sure any help is much appreciated.... oh yes forgot to say the car is completely stock no modifications done

Simple answer is no, nobody can tell you it's the rear sensor for sure without some testing of the system.

If I had to put money on it, it probably is the cat. But that's just an educated guess. Rear sensor is more than likely just reporting what it is "seeing".

markmcp · 12-03-2015 6:25pm

Thanks dieselbug for your reply much appreciated

Atlantic Dawn · 12-03-2015 7:16pm

It could be a hole in the exhaust, you should turn the engine on and listen under the car to see if you can hear anything. If not then I would look at the sensor.

dieselbug · 12-03-2015 11:52pm

Atlantic Dawn wrote: »

It could be a hole in the exhaust, you should turn the engine on and listen under the car to see if you can hear anything. If not then I would look at the sensor.

Yes, but you need to look at both sensors. (along with other things) Looking at one wont show the full picture.

A non functioning cat will result in raised o2 levels at the tailpipe anyway even if the exhaust is system has no leaks.

Subaru wrx, eml light came on

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