First Check Engine Light
 

After almost 3 years and 35,000 miles of driving and now we got the first Check Engine Light to come on with 83,000 mile total on the car. Buggers !

P1128. Bentley Manual has 2 lines printed with this code. The printed words for this code under "Fault Type" both say, "Oxygen sensing adaptation, idle range, cyl 1-3". Then under "Explanation" they say what appears to be opposite problem descriptions. One line reads "Short to ground / below lower limit / lean mixture threshold". The other line reads "Short to B+ / above upper limit / rich mixture threshold".

Nothing like having it read like it is saying something opposite. Can anyone please lead me in the right direction here ?

Thanks, Bill.

If you have a dura metric, check the resistance and then the voltage and FRA RKAT values and compare to spec. That should give you an idea.

Bill,

Here are potential faults for that code:

– Incorrect signal from MAF sensor
– Intake air system leaking
– Fuel pressure too low
– Volume supply of fuel pump too low
– Fuel injectors fouled
– Exhaust system leaking


What's happening is that the fuel adaptation has pegged the rich adjustment due to something that's causing the engine to run extremely lean (at idle speed).

As San Rensho mentioned, if you have a Durametric, you can check those values (FRA & RKAT) to see if the fault goes away when you're off idle.

Regards,
paul...

Note that only P1128 (Cyls 1-3) is being reported. This implies that the problem is only being detected on one bank of the engine, otherwise P1130 (Cyls 4-6) would also be reported. This would tend to move the MAF and fuel pressure faults lower on the list of likely causes.

Thanks guys. No Durametric, just my Craftsman OBDII reader.