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.
"Fred W" > wrote in message
. ..
>
>> > wrote in message
>> ups.com...
>>
>>> 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?
>>>
>> Jeff Strickland wrote:
>> 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.
>
>
> --
> -Fred W