check engine light and O2 sensor

[scott540]

Some of you might remember a few weeks or a month ago my check engine came on, code showed O2 sensor. Driving around yesterday I notice the light isn't on anymore. It still comes on at start up but goes out right away. Did it fix itself and save me some money?

[Tiger]

I doubt it... Our car got some very $$$ cats... if you cooked those cat, it will cost you tons more than the O2 sensors.

[John 535is (Sydney)]

The O2 sensor on mine (535) plugs into a large connector thats clippped to the left side of the engine block. The connector is a large 1/2 turn type. Mine had come loose, and I was getting erratic alarms. could be that.
Or it could be time to change the O2 sensor. They aren't that expensive and the book has them to be changed every so often (60k from memory).

John 535is

[scott540]

so any ideas why the check engine light turned off?

[DueyT]

Scott, you could do the "stomp test" to see if there is still a code in there (1212 or 1221 is L or R O2 sensor, IIRC) or if you have a 4000 (4400?) for all clear...

Cheers,
Duey

[scott540]

Thanks Duey. I guess I forgot about that. I had the 1221 when the light was on. Weird that the light would just turn off. I'll check it out.

[Rory]

Thanks Duey. I guess I forgot about that. I had the 1221 when the light was on. Weird that the light would just turn off. I'll check it out.

Scott,

The CE light is triggered when there is a fault somewhere in the engine management system. In your case you are getting a fault reported to the DME from the O2 sensor. Did the car magically heal itself? No, it is just that the O2 sensor is not reporting the fault on a regular basis. You know how your brakes start to squeal when they are on their way out rather than just losing all braking ability at once? Same principle here of being warned. If the car has 100K miles then you may as well just go ahead and change it out because it is showing signs of failure. Better to spend a little money now and have no concerns and better gas mileage than to pay too much for gas and risk damaging your Cat Converters. Good luck.

Best,
Rory

[scott540]

Scott,

The CE light is triggered when there is a fault somewhere in the engine management system. In your case you are getting a fault reported to the DME from the O2 sensor. Did the car magically heal itself? No, it is just that the O2 sensor is not reporting the fault on a regular basis. You know how your brakes start to squeal when they are on their way out rather than just losing all braking ability at once? Same principle here of being warned. If the car has 100K miles then you may as well just go ahead and change it out because it is showing signs of failure. Better to spend a little money now and have no concerns and better gas mileage than to pay too much for gas and risk damaging your Cat Converters. Good luck.

Best,
Rory

Yeah, that's what I figured. I took it for a long hard drive and the light went out so that probably had something to do with it. Gas mileage hasn't suffered yet. I just need to get over it, fork out the dough and replace them. Thanks

[malcolmX]

Yeah, that's what I figured. I took it for a long hard drive and the light went out so that probably had something to do with it. Gas mileage hasn't suffered yet. I just need to get over it, fork out the dough and replace them. Thanks

I have exactly the same problem with my 1994 540. the lights would go on, then turn off, on and off for like 1 week, then the car started doing 12 mph on a higway and the lights wouldn`t go off anymore. Car lost some power, I can tell by the way it accelerates, and it`s not the same anymore. I changed them like 15 000 miles ago with some cheap ones from kragens for 70$, now I ordered Bosch for 100$ each, hipe it`ll help