Well, my car threw its first code today, P12A9. And with my luck, while I'm out of town. I'm about 300 miles from home on business travel. It's driving strong and feels fine.

The car's had an NM Power Module for about 20k miles, and JCW Tuning Kit for almost 40k miles - all without issue. It also has a K&N CAI, for about 20k miles as well without issue.

I'm not sure what to think about it. The only other factor I can think of is a change in weather - it's been pretty dry lately, but today has been pouring and I had to drive to several large puddles - but I can't see how that would affect anything.

For now my plan is to remove the power module and take it to the local dealer on Monday, and hope it's an easy fix.


Any suggestions or thoughts?

 

I had the same setup as you for a couple of years too. Out of the blue I got a CEL, but it still drove and performed normally. Like you I removed the NM and took it in to the dealer. Turned out the NM had nothing to do with it. It was a sensor on the radiator that went bad, necessitating replacement of the whole radiator. I don't remember the code, but the symptoms are similar. I drove it for a couple of weeks like that before I had the chance to drive the 80 miles to my dealer, with no ill effects. YMMV

 

P12A9 BMW Description During the control module's shutdown phase the diagnostic function monitors the barometric- pressure sensor, intake-manifold pressure sensor, and boost-pressure sensor to determine whether they are all measuring the same pressure. The ECM sets the OBDII code when the Boost Pressure Sensor is not to factory specifications.

Read more: https://www.autocodes.com/p12a9_bmw.html

 

Are you running the NM module on the stock setting or did you turn it up?

 

Stock.

 

Update. I pulled the power module yesterday, but the light remained on. Today, I drove about 30 miles, and halfway through it turned off.

I still have an appointment for tomorrow at the dealer, and plan on bringing my car in.

 

This is the same code I've been dealing with since last year when I put the DINAN Elite on. DINAN paid to change out my boost sensor but it's still coming back.

To the OP when I threw that code and brought it to the dealer the first time they said they had to reset the ECU as it's the only way to truly get rid of the code. Even if the light goes away, it's still in there. When they did that it was the only time my car performed as I expected it to. sigh

 

Just got back from the dealer - "one time spike in boost". They reset my ECU and sent me on my way.

I'll reconnect the power module when I get back to Miami.

 

 

Welp, after a month of being well behaved, the code came back today. I cleared it and now am waiting to see if it returns.

 

And the weirdest thing - after driving around yesterday, the code went away on its own.

 

That is a Subaru characteristic right there. The ECU probably self-adjusted and it was a soft code

 

My Nm did the same thing. Sent it in and they replaced the connectors. Got the code when I hit a bump going to end of an overpass. Check the connectors-maybe wrap them in tape. Went with JCW tune and have not replaced the NM. By the way, my SA (good guy) says that BMW knows that the code is usually the added box...

 

So the code came and went yesterday. I dropped the car off to get new tires before I head up to Orlando today, and when I picked up the car, the code was there.

On the way home, I stopped at the post office, and when I got back in the car, the code was gone. It's been gone since.

I'll see what happens when I get up to Orlando. For now, I went ahead and wrapped the connectors (and also the MAF Sensor connectors, since one local miniac having the same issue has been told by her SA that it's due to the CAI) in electrical tape