For the past 6 months, I have been trying to figure out why my fuel injectors would just dump fuel into the intake manifold. Turns out I had a bad ECU. Once I installed the used ECU the car started right up and did not dump fuel into the intake manifold. I let it run for about 45 minutes to burn all the excess fuel that had been continuously dumped into the system. My catalytic converter was literally glowing hot and now I get CEL with the code 5-1-2. I know that this could be a vacuum or air cleaner issue, but I am 99% sure it is the front Oxygen sensor. I'm sure all the raw fuel may have damaged it. I have 186,000 on the car and both sensors are original. Is there a way to clean it or am I stuck with buying a new one. Also, I don't notice any difference in driving or gas mileage. Last thing.......Is there an easy way to check an ECU?

Thanks,

Ed

As far as I know, the dealer is the best place for diagnosing a bad ECU.

As for your 5-1-2, have you tried clearing it now that the engine is 'dry'? I would clear it and take it on the road to 'clean out the carbon' and see if that helps.

If there was a lot of gasoline in the manifold, you might want to change the engine oil. Raw gasoline will run past the rings and really thin out the oil.
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My name is Klaus and I am a V♂lv♂holic

Hi,
for LH3.2 control unit the 5-1-2 is set when fuel trim remains low for 166sec.
fuel trim is a measure for optimum air/fuel mix i.e. lambda=1.
possible sources: HO2S faulty, signal wire short-circuited or MAF faulty, contact resistance high.
I have twice succesfully cleaned slow operating front HO2S (200kkm/10y) sensors by first putting the sensor into carbon cleaning liquid for some time and then burning it clean with garden grill flame - do not rub the sensor. New sensor is allways new but right one.

small vacum leaks make the engine to idle uneven faster than 166 sec periods.

br Tapsa