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

With that many faults, it's probably the wiring harness. This is a very common problem for 91 - 97 MB many models. Do a search on "Wiring Harness". The good news it is an easy fix - the bad news is $600 for new harness.

It could have been several years since the codes were last cleared - doesn't necessarily point to a bad wiring harness. The first step is to clear all the codes, check it to make sure they are all cleared, drive the car a while and check them again.

Record the codes.....Clear the codes ...Might clear up some drivability problems....recheck next time MIL comes on.

MAS do have high failure rate...O2 not so often...drive the vehicle for about 20 miles at all speeds and throttle openings to allow it to re adapt...might take more then a few drive cycles....wire looms are common problems..( pattern failures.)...throttle adaption needs reset....then recheck codes.

We await the results.
.

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Most Codes that trigger the CEL are cleared automatically if the problem goes away. Usually the CEL triggers if a fault is detected for 2 consecutive -ignition on-. If the fault clears it may take 3 or 4 consecutive -ignition on- for the CEL light to go out. Reset the codes as suggested. You will know right away if you have shorts in your harness. Intermittents are another matter.
I went thru the exact same ordeal last June. I could get the CEL out but never got the drivability - O2, MAF, Injector and CAM solenoid codes kept kept triggering the CEL over a two week period.

On 104 HFM /SFI systems , [93 thru 95] AIR code coupled with EGR code and 02 sensor is usually a split/broken vac feed line that crosses the front of the engine
[ under front cover] over to the SOV valves for EGR/AIR . This line feeds both of these , so if it is cracked [which happens all the time b/c they are plastic] , then BOTH those codes will pop and they are both emmisions codes , so they pop the CE.
If you find this to be the case , simply replace that hose with a rubber one.
The 02 sensor also faults b/c the self test for AIR system is ECU monitor of 02 signal for AIR activation. [ looking for lean condition]

Thank you for all the replies. I will first clear all the codes and see what comes up.

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tgmiller77
1997 Land Rover Discovery 158,000
1995 E320 Wagon 132,000mi
1999 E320 Wagon 97,000mi

Cleared all the codes and checked the connection to the MAF sensor and it was not snapped in fully. Guess it just wiggled itself out over time. Light off for now with all codes cleared. Thank you for all the replies.

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tgmiller77
1997 Land Rover Discovery 158,000
1995 E320 Wagon 132,000mi
1999 E320 Wagon 97,000mi

Watch for new reoccurring codes . A MAF circuit fault will not bring up either an EGR or AIR code.

The CEL has come back on twice since the origional post. Both times codes 2(o2 sensor) and 5(egr faulty). It does have 125,000 on the clock. Could a bad oxygen sensor cause the egr code? If it is the o2 sensor, what is the most obvious place to start. How many o2 sensors are on a 1995 e320? Should I replace all of them or is there one that is most prone to failure? There is no noticeable change in the car and when I clear the codes the light might stay off for a couple of hundred miles. When it does come on it usually comes on at a warm start. Thank you again.

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tgmiller77
1997 Land Rover Discovery 158,000
1995 E320 Wagon 132,000mi
1999 E320 Wagon 97,000mi

There's just one O2 sensor. It's a 60k mile item. If you don't know the history of it and you're getting the fault code that's a pretty good place to start. It's fairly easy to replace.

Here's a link to your DTC #5 . . . plugged egr tube. . .
94 e320 EGR tube cleaning How many hours to do?

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Regards . . . . JimF
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'94 S500 Cpe

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