Oxygen sensor light

[GotTheBenz]

My oxygen sensor light remains on even after changing the oxygen sensor. What does that mean?

[jhodg5ck]

It means pull your bulb...early cars O2 systems are very rudimentary..

I believe after 75K the WIS states to pull the bulb.

Jonathan

[zviratko]

o2 sensor has a warning bulb?? where?

[wbain]

On our cars, it's called the check engine light. It's really the O2 sensor change light. The light, coupled with the duty cycle on the X11 connector, will tell if the ECU is bad.

I've been through this with my 420SEL. I'm getting a replacement ECU soon.

[jhodg5ck]

It's different on the gen I cars..works through tweaking the frequency valve instead of feeding tweaking the EHA.

I believe the light is actually on a mechanical trigger, thus the pull the bulb reference in the service literature.

Jonathan

[marlinspike]

The light in the Gen 1 is on a mechanical trigger togo off, IIRC, at 60k miles. The official replacement procedure involved removing the bulb from behind the dash.

[emagic]

Unplug the battery (negative cable) overnight. Put it back on in the morning. It will reset the "check engine" light.

[jhodg5ck]

It's going to be mighty hard to re-set a mechanically triggered CEL/O2 light by unplugging the battery.

Make sure you have your code if you still have the factory becker installed...sometimes the dealers are fussy in giving out said codes.

Jonathan

[emagic]

It worked on my 91 560 SEL. Change the O2 sensor, light still on, disconnected the battery overnight. Connected it back on in the morning. Start the engine, wallaaaaa...... light off. Don't know whether it will work on yours though.

[dave420]

READ, guys. Jonathan said it's different on the Gen1 cars...

Dave