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

My son has a 98 Escort GT. 2.0, the check engine light has been on for a while with the code P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2), but the car still ran ok. Just recently the car
started fine and he drove about 1/4 mile and the engine quit, it would not accelerate. Once the car cooled off it would start again and do the same thing. I checked the codes again and an additional code was there (PO136), which was the 1st o2 sensor. I changed the 1st sensor and the code went away, but the car still has the same problem it shuts off after a 1/4 mile or so, the 2nd code is still there. If I change the 2nd sensor will this fix the problem or could something else be causing the car to stop?
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And you want BMW owners to help you how?
FloydR
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Floyd Rogers wrote:

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

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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.
--
-Fred W

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I don't believe that the O2 sensor has sufficient 'authority' to change the mixture enough to cause the car to stop running. I had a situation once where a mechanic destroyed the threads in the manifold while attempting to replace my oxygen sensor. I had to drive the car for 3 weeks with no oxygen sensor and a plumbing plug stuck in my exhaust manifold. My mileage went down by about 10% but the car ran just fine. 1984 318i L-Jetronic.

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Jack wrote:

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.
--
-Fred W

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

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Jack wrote:

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

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