[EatMoreLobsters]

A few weeks ago when the weather hit in the 90's for the first time I noticed my car limping when I would run it harder than normal in 3+ gear (on the street, not track). Limp mode did not actually engage but going full throttle for a few seconds would noticeably pull back and give the same feeling as limp mode. My oil temps were fine. AC was on.

The check engine light came on when I pulled into my driveway after lunch, no faults or issues show in idrive though. So i plugged in an OBDII reader and get the following diagnostics


- Fault: Engine cooling system: shutdown coolant pump for blocking
- Code: 20A804
- Fault: Power Management: quiescent current of injury
- Code: 213601
- Fault: Air mass plausibility: air mass to low
- Code: 102002
- Fault: Throttle angle - intake manifold absolute pressure, Comparative pressure too low
- Code: 101F01

After that I let the car sit while I finished the work day. I got back in about 5 hours later and there were no more codes or check engine light, but still i drove the car conservatively for the next week or so with no repeat issues even when the temp was 80-90+ out. It's been much cooler since then, in the 60-70 range and putting the pedal down has not shown any issues - Until tonight. I planned to take it in to be inspected, but did not since all seemed fine - I probably should have either way.

(AC/HEAT WAS NOT ON entire day) I was at a drag strip, the first few runs were no issue - waiting about 20-30 minutes between runs. Then on the 4th go down I noticed the same limp feeling as I when I probably hit about 80 mph the power significantly decreased, acceleration did continue but not at a normal pace. I pulled off and ran the OBD again and saw my coolant temp was 245 so I ran the diagnostic to see if there was any further details since the idrive had nothing and came up with this one:

DME/DDE interface: Forced upshift due to thermal engine protection request or signal invalid (switch status, warm-up, powertrain, 0x3fb)
code: 421722

As the night went on, I let the car sit for about 3 hours and hit the track one more time for no issue and drove 90 minutes home.

It was 73 degrees today during the day, cloudy eventually dropped to 60. I understand that a 1/4 mile on full blast can ask an engine to do more than it's supposed to, but this has not happened before. I searched around the internet and have not found anything that I would deem conclusive as it seems a lot of people confuse oil and coolant temps.

I know water pumps are one of the monsters in BMWs closet but I'm not convinced that is the case. I've seen a few articles on people upgrading radiators to solve the probably, but again that was riddled with confusion over what was running hot. I've also seen people claim that when upgrading the intercooler (which I have) there have been issues with the fans, but my gut tells me that is not the case.

Any thoughts? Has anyone else experienced this?

Hopefully I can get this figured out before summer gets here.

[RoundelM3]

If you have an M-Sport model, there was a problem with the aux coolant radiator fan that required replacement (mine needed this twice). It caused some of the issues you are experiencing, so if you haven't had that done yet, you might check into it. Also, you're running a bigger turbo and more aggressive software, which can affect oil temp more so than just the engine coolant temp, and that's another item that will signal the DME to pull things back.

Also, your CAI may be causing your MAF issue - there have been discussions regarding aftermarket intakes producing this type of problem, so check the N55 engine section of this forum for more info.

[EatMoreLobsters]

Originally Posted by roundel335

If you have an M-Sport model, there was a problem with the aux coolant radiator fan that required replacement (mine needed this twice). It caused some of the issues you are experiencing, so if you haven't had that done yet, you might check into it. Also, you're running a bigger turbo and more aggressive software, which can affect oil temp more so than just the engine coolant temp, and that's another item that will signal the DME to pull things back.

Also, your CAI may be causing your MAF issue - there have been discussions regarding aftermarket intakes producing this type of problem, so check the N55 engine section of this forum for more info.

I'll check the fans, but I don't have the m sport. Just sport line. Oil temp has been perfect hanging around 220. Did you get any warming in idrive when your fan went?

[RoundelM3]

Originally Posted by EatMoreLobsters

I'll check the fans, but I don't have the m sport. Just sport line. Oil temp has been perfect hanging around 220. Did you get any warming in idrive when your fan went?

First time around, yes - I got a "drivetrain malfunction". I checked codes, and sure enough, it pointed directly to that fan. The fan and radiator are all one unit, so it had to be ordered. Second time around, maybe a year later, no warnings, just the drop in power and the main radiator fan running at top speed (you could feel and hear it in the passenger cabin). Code check showed the same thing. When that fan goes out, DME panics and thinks there's a major fault in the cooling system and tries to compensate, hence the overspeed on the main cooling fan.

[paul e]

Always a good idea to bring a car with potential cooling issues to the track.

I guess it is true: you can't make this stuff up.