P01 / P59 Part 1:
The P01 and P59 have gotten some love over the years. This controller is not as nice regarding idle control strategy. GM used a table called Throttle Cracker to handle airflow once the vehicle was moving. That caused serious issues:
1) idle too high when coasting
2) dies on coast-down
There are band-aids — like forcing idle spark at any speed — but that brought a “trailer hitch” feel. So what is worse: trailer hitch, or an unsteady idle?
We solved it by rewriting most of the idle routine to work very similarly to the E38.
Number one: we added Idle Airflow vs RPM. That fixed the case where RPM drops too quickly and there is not enough time to recover before the engine stalls.
Part 2 solves the trailer hitch.
Originally posted on Facebook: https://www.facebook.com/photo/?fbid=122109571598823877&set=a.122103612038823877