OK, I'm stumped. Last week on my wifes '05 Pac (28k miles) the CEL came on and at the same time she noticed that the cruise control stopped working (no instrument panel lights come on when CC button is pressed - nothing). In addition to cruise control not working the car ran like sh*t. Almost stalling out when idling at stops, etc.I ran the codes and came up with 4: P0129 (x2), P0300, and P0113. The P0113 pointed me to the AIT, so for $30 I replaced it. After changing the AIT the P0113 and the P0300 are gone and the car runs better but not perfect. Itno longerseems to want to stall out but it idles funny,sort of pulsing up and downlike someone is feathering the throttle and has trouble starting (both are now intermittent). The cruise control still does nothing, no lights on dash. And I still have 2 P0129 (Barometric pressure low) codes. Seems to drive OK at cruising speeds but shows the symptom (revving up and down) at idle and occasional hard starts. Should I change the MAP sensor? I hate to take a $110 shot in the dark... and what's the link between AIT, MAP and cruise control all failing simultaneously? Please help. I can't afford an inflated "dealership repair" charge on this right now and she needs her car to be reliable for running our two little boys around...

 

OK - I'm kind of surprised by the lack of feedback here but anyway I thought I'd post my resolution for posterity. Recap: Check engine light came on out of the blue one day and the car immediately ran like sh*t and the cruise control failed entirely. Checked codes and we had P0129 (x2) P0300 and P0113. P0113 refenced the AIT sensor specifically so for $30 I replaced it. After replacing the AIT we still had a C.E.L. but two of the codes had cleared (the P0113 and the P0300) leaving me with just the P0129 (x2). By the way while the car still ran poorly it was much better at this point. Now what to do with the P0129, which stated barometric pressure low? I was fearful of a vacuum leak but after a very low tech assement and a pretty throrough examination of the lines, connectors, etc. (particularly at the vacuum reservoir right under the battery tray) I suspected vacuum was OK. At this point I suspected the MAP sensor but at $110 I really hated to buy it without being sure. Without any other avenue to pursue I took the chance bought the MAP, plugged it in and low and behold no more P0129, cruise control functions fine and the engine is running smoothly. So for a total of $140, the car seems perfect but it does beg the question "what caused the simultaneous failure of these two (pretty costly) sensors. Is it the notorious "carbon build-up" that these motors are famous for? That would be may (uneducated) guess. If I'm right, then I've only corrected the symptoms without addressing the root cause and it's likely only a matter of time before I have to shell out another $140 to keep this thing running. Unfortunately I won't be able to let you know how long that is since I intend to get rid of it - quickly. IMO: the Pacifica isa badmix ofunderpowered and inefficiency (i.e. bad mileage with no go). In addition I believe it has serious quality issues, above and beyond my problems outlined here, which will translate into a very high cost of ownership. We were lured in by the cars' size and good looks but in hindsight I consider it's purchasea mistake which I intend to rectify ASAP.

 

Thank you for your recap. I am having the same issue and my code was 129 as well. I feel a lot more comfortable getting the sensor. How hard was it to install? Any tips would be greatly appreciated...