Originally Posted by tommyp

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?