Any idea what this code means?

[DennisG01]

The "Service Engine Soon" light came on as I was driving. It stayed on for about 120 miles over 2 days, then went out. During that time there was absolutely no decrease in performance. While it was still lit, I stopped by an Autozone to have the code read. They only have a basic reader - I'm taking it to a garage on Thursday for a tranny service so I'll have them check it also, but it's the first time I've been to this garage. I was wondering if any of you know what this code means, and since the light went out by itself, could it be some kind of loose wire? I checked fluids and fuel cap, everything is normal. The code read "P0236 Turbo/Super Boost Sensor A CKT Range/Performance"
Thanks!

[ucdavis]

"The PCM operates a solenoid to control boost. This solenoid is normally open. By providing a ground path, the PCM energizes the solenoid which then allows a vacuum to pass to the wastegate valve. During normal operation the PCM compares the wastegate duty cycle with the boost signal and makes corrections in the duty cycle accordingly.
Conditions for Running the DTC:
~ Engne speed > 2400 rpm, and
~ fuel rate >20mm OR
~ Engine speed >1800 but < 2400
~ fuel rate >20mm
Conditions for setting the DTC:
~ boost <, >, or = to 20kPa from desired (internal to PCM)
~ all diagnostic conditions met for 10 seconds"

Vacuum leak or pinched line could be the trouble. Also solenoid filter, solenoid itself, or boost sensor (that's what the PCM is comparing with) if you have boost, but no signal to the PCM (you need a scantool to read the boost sensor while running rpm's to 1500 then back to zero to observe change in boost; if none, bad sensor). Vacuum source is next thing to check. Normal vacuum is pulsed to the wastegate, so steady vacuum reading (on gate side of solenoid) indicates a restricted solenoid vent filter (small sponge thingee on solenoid) or solenoid vent orifice (under the sponge, I think). Vac @ the gate should be >15 psi @ idle & fluctuating, and , steady @ about 22 psi from the vac pump.
That's all I know.

[DennisG01]

ucdavis:

That's all you know? Shoot, that's quite a lot! Thank you for the detailed information. It will help me when I take it into the garage on Thursday. smile.gif