Do I have to replace a california emissions cat and O2 sensors on a 1998 bmw 318ti with the same thing?

25

Asked by Sep 07, 2007 at 04:51 PM about the 1998 BMW 3 Series

Question type: Maintenance & Repair

Hello,
I went with an after-market cat and O2 sensors and now I'm getting a check engine light.  The code reader is showing P0135 O2 sensor heater circuit (bank 1 sensor 1) and P1186 O2 sensor heater control circuit (bank 1 sensor 2)
The car is still running like a top, no rough idling, plenty of horsepower, no heavy smell out of the exhaust...etc. Before I made the change there was no check engine light but the material inside the cat was all broken up and making a hell of a racket.
What do you think happened?
Thanks.

Don

1 Answer

41,475

Most likely you will need a California cat and O2 sensors. It is not unusual for the material inside the catalytic convertor to break down; there may even be a recall on them as there was on certain Jeep vehicles in the 1990s. Aftermarket cats do not contain as much of the platinum catalyst as the OEM cats, this is why they are cheaper, but may also be why you are having problems. However, your codes don't directly relate to the readout (rich/lean mixture) from the O2 sensors, so it is possible a wire has been burned or shorted causing them not to read properly. Have this checked by a mechanic.

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