P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

wrote

And you want BMW owners to help you how?

FloydR

I suppose we could suggest the fuel filter might be clogged, but then someone in alt.autos.ford could have a better idea ;-)

Andrew

The HEATER CIRCUIT MALFUNCTION error means that the built-in heater inside the sensor has failed. The only recovery from this is to replace the affected sensor. Having said that, this is not an error that should result in your car shutting down.

The sensor works when it has reached a certain temp. This temp will easily be reached through the passing of the exhaust stream, but the rise-time is too slow. The computer wants to see a valid input faster than exhaust stream will heat the sensor -- the problem here is that the sensor is needed to reduce smog, and a cold sensor will not reduce smog so they heat it by internal means to get it to work. The internal heater is broken.

Neither code you reported should shut the car down. Of the two, the second might result in the car reverting to Limp Mode, where it runs crappy -- and rich (too much gas is fed).

Adding to what Jeff has mentioned, the first O2 sensor is the one used to tell the ECU what the exhaust mixture is, and thereby allow it to trim the fuel injection for the proper richness. The secind sensor is only used on 1996 and later OBD2+ cars to tell the ECU how well the Catalytic Convertor is cleaning up the final emmissions.

So the engine should run just fine with a bad 2nd sensor, it would just throw check engine codes.

The fact that the car runs for a few minutes and then craps out is consistent with your O2 sensor problems. The engine starts and runs "open loop" for a few minutes until the ECU figures the O2 sensor should be up to temp. At which time it tries toi use the sensors feedback to adjust the fuel injection for optimum mixture.

Well my experiences with 2 mid 90's BMWs say otherwise. The engine will be so messed up it won't idle, and will stall. It also wouldn't accelerate much if you try just holding down the pedal.

So it would be really easy to find out if unplugging the sensor had this effect if someone had such a car available.

Perhaps. But a faulty sensor and an unplugged one may give differing symptoms.

change other o2 sensors...clear all codes..make sure you change the oil...very important