2-2-1 Diagnostic Code ('91 740) - and a question
 

I have a 1991 740 Wagon (non-Turbo) and the check engine light is on. I checked the code and got 2-2-1 (using port #2). This was the only code. Based on some online research I think this is a O2 sensor code. Is that correct? If so, where is the O2 sensor located, and how difficult is it to replace on my own?

Could the code mean anything else? What about searching for codes on the other ports?

I reset the code and the light went off, only to come back on after about 6 miles of driving.

Thanks!

2-2-1 for Bosch LH2.4:
Fuel trim (lambda control) too lean at part load Lean; air leak; low fuel pressure; bad AMM Engine stops when starting from cold; high fuel use

2-2-1 for Regina Fuel Injection:
Oxygen sensor not operating Oxygen sensor or intake air leak

I'm not sure what the Regina system looks like. The way to check a O2 sensor is to measure the voltage on the big green wire with everything connected, during idle. It should swing quickly between .2 and .8 VDC.

Bosch or Regina?
 

I think I have the Bosch LH2.4 but I am not positive. How can I be sure?

Also - check out the attached pic. The corrugated hose in the photo has a small hole in it. What is this hose? It runs from the air filter box, behind the radiator, and connects into the passenger side of the engine.

Thats the pre-heat hose, which allows in hot air when the temps are cold. The problem is the thermostat in the air filter box can stick open and the hot air will cook the air mass meter.

If you have a Bosch air mass meter (with the part number ending with 016) then I'm pretty sure you have the LH2.4 system.

Look for split vaccum lines and hoses.

See photo - this is where the AMM should be, right? I looked at photos online and this doesn't look like an AMM.

This Regina, Bosch LH2.4 discrepancy is confusing me. I've been trying to read descriptions on brickboard, but it's a little too technical.

On another note - where does the wire that comes out of the O2 sensor attach?

Thanks!

now I am also getting a 1-2-2 code. I can only find reference to this for the Regina system. Air Temperature Sensor. I think that is what is pictured in the post above. Thoughts?

Here is the regina o2 sensor:
http://www.fcpgroton.com/product-exe...ategory_id/169

The output wire is the one by itself. It will mounted in the exhaust header by the engine or near the cat. converter, but the connection should be on the firewall.