Last week the check engine light came on on my 95 E320 wagon it has 123,000 mi. Ordered a diagnostic code reader on ebay and this is what came up on pin 3: 4-air injection system faulty mass air flow sensor; 5-EGR faulty; 12-oxygen sensor. Could all of these fo bad at the same time??? What should be my first course of action? Should I replace the O2 sensor first and clear the codes to see if that will fix the problem?

Also on the 14 pin I had an 11-closed throttle recognition signal to ECM

I can definately tell the car is a little sick, especially at a cold start.

Thank you, Greg

1977 450sel 162,000
1995 E320 Wagon
1998 E320