Got a check engine light P2251 and SH-AWD 77. When P2251and SH-AWD 77 comes on, it disabled the awd, turn off the engine then back on to clear it except the P2251. Based on the research its the oxygen sensor top rear engine. Inspected the wiring and no visible cut/open. Ordered part 36531-RCA-A02 for $210 includes shipping and taxes.

 

I just had the same message come up plus the "Check the SH-AWD" message at the same time (2 at once!!). Not sure why both would suddenly appear. I may need to run to Autozone and see if they can read the code(s).

Has anyone ever had both Emission and SH-AWD come up at the same time?

 

Yes. My problem was a gas cap that I had dropped. Replaced it. Within 15 minutes the codes cleared themselves.

 

Thanks, may try that too. I did notice that when I opened and then retightened the cap, the codes went away for a while, but then came back. I guess an OEM cap is best?

 

My RL has expensive tastes. I replaced mine with OEM. But, I suspect aftermarket may work just as well.

 

I once had a pressure switch problem with the transmission. It lit up about three items on the display's amber Christmas tree of alternating warnings, including SH-AWD and something else I forget. My Indie mechanic said it wasn't the first time he's seen a carmaker choose to light up irrelevant warnings just to make damn good and sure the owner woudn't even think of not having it checked out. I wonder if that happened here.

 

Got a new gas cap, which I needed anyways, but it isn't clearing the codes. Guess I go find out the codes tomorrow. Could be O2 sensor, wire, bad battery (only 2 years old), alternator or ??

 

Give it a little time. Sometimes the gas-cap code doesn't go away until a couple starts and 20+ minutes of driving later.

 

Agree. Different cars take differing amounts of time to self-clear. Makes you appreciate it even more when it does clear.

 

The code will be on ur navi messages.

 

The part arrived yesterday and i just installed it today and cleared the codes. If anyone of u will do this task, its a pain to removed the connector. U need to remove the connecter where it was attach to the engine first by using a flat head poking it side ways. Since the connector has been there for yrs u need the flat head to push the connector to unattach it.

 

not seeing any codes on the navi.

The SHAWD code went away, but the Check Emissions light is still there after taking a drive. Will give it more time.

 

The SHAWD was the first code to self-clear on my RL.

 

 

Got the codes, P0154 for Emissions and 77 for SHAWD.

Now I have to figure out if that means O2 or what

 

B2S1 O2 sensor? The one right in the front? Go OEM or aftermarket?

 

Based on what i read this is the front oxygen sensor cat upstream at the front engine. Go oem.

 

Called dealer for the part, they wanted $342 just for the part. Looked on Rockauto, it was $88 plus $15 for shipping overnight for same oem part (brand is NTK). Ordered a $9 special socket on Amazon. Took 15 min to install, super easy. Took negative off battery for 5 min, message all gone. Took me more time to reset navi, radio codes, seat, XM etc than O2