I started my 850 yesterday and noticed that the up arrow shift light for the transmission was flashing. I received the following codes: From socket A1 131 & from socket A2 121. I let the car sit for 45 minutes and started it. The transmission light was no longer flashing so I drove it home. I only had one incident of a loss of power that was corrected by pushing on the gas pedal for a few seconds. It did die twice while idleing at a stop light and it seemed to be a little harder to start.

This brings me to my questions. My book says that 131 is " A break or short circuit to ground in the STH circuit." What is & where is this STH ciruit? Is in on the inside of the tranny or a sensor on the outside?

The books lists error code 121 as "MAF sensor signal absent or faulty." I know that MAF is the Mass Air Flow sensor and I know where it is located...the top of the air cleaner housing. Question is, is there a way I can test this sensor to make sure that it is bad before I buy a new one needlessly. I have already got a quote of $300 plus for the sensor so you can understand my reasoning in wanting to make sure it is bad. I have found an entire air cleaner housing at a junk yard for $100. Does anyone see a problem with using a used MAF sensor?

I have not had a chance to clear the codes and drive it again to see if the errors appear again. Any help would be appreciated.

Note: the car has cost me a few bucks lately. Timing belt, serpentine belt, water pump, idle pulley for timming belt, one injector, crank sensor, and camshaft position sensor have been replaced the last month. The car has 165,000 miles on it. This is the first bit of trouble I have had out of it.