I have been dealing with a check engine light on my 1991 190e 2.3 for a while now.
It is a California car so I can check the blink code light under the hood which always reads 5 blinks, meaning a problem with the o2 sensor.
I have replaced the o2 sensor and also its cracked exhaust manifold but still no luck. Anyone have an idea what could be the problem?

Do you have any stored DTC's?

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Yes, the LED code reader blinks 5 times meaning there is a problem with the oxygen sensor.

I forgot to mention earlier that it has a 1990 mustang bosch oxygen sensor spliced into it which from what I've read should work fine.

If you clear the code, does the CEL come back on?

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible

Your power wires might be reversed. The two white wires have to be in correct orientation or it wont power. That may be the reason the light is still on. When the engine is stone cold. go turn the ignition on and get under the car and wait and feel if the O2 sensor starts getting hot. If it dos not, reverse white wires and try again.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

I also have a CA 1991 190E 2.3 with a check engine light on. I cannot get the test LED to do anything. The service info says that a condition is that the check engine light must be off. How can I do that without also clearing the codes? Thanks.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Turn key all the way to the right, but dont turn on the engine. Go press and hold the LED button for 3-4 seconds and release. After the light is done blinking. Press and hold the LED for 10-11 seconds. There will be one long blink. Do this untill the LED only blinks once after holding the button 3-4 seconds. In the future do a search and if you can't find the answer, you should create your own thread instead of hijacking one. Cheers.

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1990 190E 3.0L

First, sorry for the 'hijack', but since the topic is the same and the date current, why are you upset?

Anyway, what you suggest I have read before and tried repeatedly before posting, and no blinking at all. As I said, the service docs say that FIRST the check engine light must be off. THAT is what I find confusing, so my question - to re-phrase - does the light actually need to be off first, or am I misinterpreting that? If not, is there a way to turn it off without disconnecting the battery and thus re-setting the codes. Or, am I dealing with a mal-functioning LED diagnostic circuit?

If anyone has the answer or other useful suggestions, I would much appreciate. Thank-you.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Thanks for the advise. I didn't know the orientation of two power wires mattered and could have them reversed, I will switch them tomorrow.

Does anybody know the model number of the mustang bosch o2 sensor that works on the 190s?

1990 5.0 Ford Mustang

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1990 190E 3.0L

As long as its the 5.0L 1990 Mustang GT sensor 3-wire its good.

No need to reverse the wiring until you know if its heating or not. If you reverse the wiring, you'll end up doing it again if the heater circuit is bad. So first see if it heats in its current orientation, then switch it and test.

Should save you some time.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Hello again, its been awhile since ive dealt with my O2 sensor on the 190 but it is still not working and I have an emissions test coming up.

The sensor was not heating so I switched the white wires orientation but still no luck. Its throwing the same 5 blink code. Is there another link in the o2 sensor system that could need replacing?

just go to your parts house and order one for a 1990 mustang with 302 and ask for the up stream ox, mine was fourty bucks.

I saw that post and it is wrong in my opinion, first the two wires are part of a continuing circuit, they are white those two wires run the heater in the ox, makes no difference in position, now to clear up another item, the heater gets its power from the fuel pumps you will not get heat until the engine is running. The third wire is black and it connects to the green wire, this is the signal wire for the EHA. clear each code after you have read them and all should work. I just finished this on my wifes 190E and will post every thing I did in a couple of days, it might help.