This function is handled by the EDS system, which is a pretty complicated thing to troubleshoot. Doesn't usually go bad. There's a solenoid on the back of the IP that controls the position of the rack, a computer behind the battery, various temperature sensors and the air mass sensor. It's not covered by the FSM, the documentation is in one of the service bulletins. They're available through WIS-net, but I think you have to pay for access.