05 Mini S w/ 75K. This is happening every so often. My son is getting the CEL and the codes are P1688 & P0500. When this happens it goes into limp mode....any suggestions?? I just replaced the serpentine belt yesterday, it broke and was very brittle. Im assuming it was the original belt. I'm hoping its the DT bypass valve. Is there any way of being positive??

 

I'm in about the same situation. Belt broke yesterday and was replaced. If I accelerate too much, it goes into limp mode with the same codes. I suspect the new belt is either too long and slips with acceleration or is misaligned.

How did you resolve yours?

 

Whats happening is your harmonic balancer (crank shaft pulley) may be separating. When you release your tension pulley its apply just enough pressure to prevent the balancer from completely slipping all of the time. When you attempt to accelerate, the rotation of the harmonic balancer is too fast for the tension pulley to keep suffient tension on the bad balancer. So it starts to slip. When that happens every component on that belt is effected. Water pump, oil pump, power steering pump, alternator.....they all completely stop spinning or at the very least slow down significantly. Pull your belt and grab your balancer and wiggle it. If it moves at all in any direction its bad.

 

I sure hope it's not the harmonic balancer again. I just replaced it about 10k miles ago. I'll take the belt off tomorrow and check.

If it is the balancer, it may be that something like the alternator air conditioner or supercharger is creating more drag than normal and causing it to fail prematurely. Argh!

 

I just read a different post that could explain the failure of a fairly new harmonic balancer. Evidently, when a belt breaks, the belt tensioner slams into the harmonic balancer and wrecks it. The installation of a tensioner stop would have prevented that from happening.

It looks like I may be buying a new belt tensioner, a new harmonic balancer and a tensioner stop. Dang!

 

You can see grooves where the belt tensioner was rubbing on the belt less crank pulley (harmonic balancer)