04 Saab 93 Aero convertible.
This car and I are engaged in a chronic battle regarding the P0687 code. It seems to be a ghost code.
Normally, it trips the code, goes into limp mode (no turbo boost, reduced throttle response) and kills the a/c. I reset it with my handy android phone and the torque app and all is good. Now it may reset the code instantly and we get into a pissing contest about how fast I press the reset button vs how fast it can reset the light. Which makes driving highly entertaining as the turbo boost kicks in and cuts back out. None the less, it is resetting the ecu, producing the not-ready state for things like catalytic converter and such.
BUT...
Every once in a while it will trip the light, and not let you reset the ecu.
In this case it usually will not be in limp mode and will not have killed the a/c. But you pressing the reset button does nothing. None of the readiness states are changed to not-ready.
In fact, it will continue along quite merrily, and even continue to change earlier not ready states into ready states!
So it's tripped a ghost code (P0687), turned the check engine light on, and ignores all inputs to reset and drives just fine.
Then, some time later it decides to behave normally and you can reset it. Or sometimes it just turns the light back off all by itself and shows no code or legacy code.
Other than just throwing another ecu at it, anyone have any thoughts or knowledge?
