I got the check engine light and pulled off these four codes from the LED. I can see that oxygen sensor might be bad as I've been suffering bad gas mileage, but what's 3,4,5 got to do with it?

Any suggestions?

Thanks
95e320

1 No Fault Found
2 Heated oxygen sensor faulty
3 Lambda control faulty
4 Air injection system faulty hot film mass air flow sensor with hot wire
5 Exhaust gas recirculation faulty
6 Idle speed control faulty
7 Ignition system faulty
8 Engine coolant temperature sensor open circuit
9 Intake air temperature sensor, open circuit
10 Voltage at mass air sensor too high/low
11 Tn-signal (rpm signal ) at engine control module faulty
12 Heated oxygen sensor heater circuit open or circuit short
15 Injector, cylinder 2
16 Closed throttle position information faulty
17 Data exchange malfunction between individual control module
18 Adjustable camshaft timing solenoid circuit open or circuit short
19 Injectors circuit open or circuit short emission control module adaptation in engine control module at limit
20 Vehicle speed signal not present
21 Purge switchover valve circuit open or circuit short

EGR may be plugged (DTC 5) but more serious DTC 3 and 5 mean MAF bad??? Thus no Lambda.

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Regards . . . . JimF
-------------------
'94 S500 Cpe

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All other codes except 5 can be triggered by a faulty O2 sensor.

The secondary AIR system will pop the CE light because the system AIR check requires a proper lean reading from O2 sensor
to pass the ECU operation test. So bad sensor will show a fail condition on AIR ...
This system does not use Hot Wire Mas [ LH-SFI], but rather Hot Film Mas [ HFM-SFI]
The Egr fault is most likely a plugged EGR tube at the engine end of the EGR pipe.
Check archieves for other post on this common fault/repair...
[There was also a part change
on this year EGR for sticking valves]
An easy test is to supply vac to EGR with hand pump at idle and watch for poor idle w/vac applied... this means valve working and tube open..
Recommend changing O2 , erasing all codes and see if any come back after part change...