300SE 1989 or similar Check engine light

[unkl300d]

The search function was not operational so I could not search archives.

Is there a way to get a CEL diagnostic code by switching the ignition key on/off several times and reading the light blinks on the dash?

Does anybody have the code sequence for the O2 sensor etc??

Thanks

1989 300SE with check engine light on.

[deanyel]

Do you have an 8 pin diagnostic connector in the engine compartment? Is your car CA version?

[david s poole]

on an 89 300sel when cel comes on it means only that 02 sensor is bad,02 sensor is disconnected or engine is running way too lean or way too rich.

[unkl300d]

This car is a California version and does have a connector for a diagnostic tool. I have not counted the pins.

The o2 sensor was replaced about 2-3 yrs ago and not many miles have elapsed, say 8K. This does not exclude the O2 sensor of course.

The owner manual also implies that the O2 sensor may be at fault when the CEL goes on but says to have it checked, apparently for other possible stuff.

Can STP injector cleaner cause this? One std. bottle treatment in one full tank.

[deanyel]

That should be a 60k mile O2 sensor. You might want to try reading the codes at diagnostic connector - a CA version 89 should have an 8 pin connector. There's one pin for the engine with maybe 10 or 12 fault codes. There should also be pins for the AC and the SRS. It's not terribly sophisticated in that era but better than nothing.

[unkl300d]

The replaced O2 sensor was done 4 yrs ago, 16K miles ago.

Thanks for the opinions so far.

I just thought I recalled that one could activate code sequences by turning the ignition switch on/off several times without needing a meter device.

Any clues?

I don't feel like buying an el cheapo or otherwise meter. The next step would be to have the mechanic fix it.

So, I am trying to gather info to see if I can do it myself before handing it over.

Thanks

[cool]

unkl is that morse code (the think with the blinking) NO SUCH THING>

[deanyel]

Try a search for fault code reader, aka Arthur Dalton code reader. You can build the code reader yourself with inexpensive parts from Radio Shack. Here's some more info on 8 pin code reading including the list of faults on CIS pin 3.

http://mywebpages.comcast.net/chwilka/Error_Code%20_reader_reset_tool.htm#Reading%20SRS%20Codes%20(copied%20from%20MBCoupes%20archive,%20e mail%20sent%20by%20Randy%20D.)

[unkl300d]

Follow up,

Whay I di was disconnect the battery for 30 min plus. I also tapped on the O2 sensor and surrounding exhaust pipe to possiblt rid any particles that may have stuck. If any.

The CEL has gone off and so far (10 miles) has stayed off.
However, if a fault exists, I can expect it to go on again after 30-60 miles.

I'll follow up.

Thanks for the DIY meter link and opinions !!

[A264172]

To read your codes, there is info in this link;
http://www.peachparts.com/shopforum/showthread.php?p=742563#post742563

...on some codes that may or not apply to your car,.. and on how to build a cheap code reader that will read your codes... if your car was produced for California ...

there are also schematics, 10 sheets, on how to read your codes (from the MB manual) in the links at the bottom of my sig line.

Best of luck. These emmissions falts can be tricky and or real simple.

[unkl300d]

Thanks Marty.

So, far so good with the W126.