Buick Park Ave code 42 "EST"?

SOURCE: 98 buick park ave, hard to start, run's rough. po172 code

oxygen sensor in exhaust

SOURCE: power door lock switch replacement

Remove or Disconnect

Door handle trim plate.

1. .Install or Connect
   
   
2. Electrical connector and door lock cable.
3. Trim panel by engaging hooks on backside of panel.
4. Push pin fastener in defroster duct.
5. Screw from behind lamp assembly.
6. Courtesy lamp assembly.
7. Two screws in arm rest.
8. Arm rest cover plate.
9. Door handle trim plate.

1. Trim panel. See: Doors, Hood and Trunk\Doors
2. Four tabs retaining switch.
3. Electrical connector.

1. Electrical connector.
2. Snap switch into trim panel.
3. Trim panel.

SOURCE: 92 buick park ave security light on car wont start

Someone put the wrong key (resistor value) in the ignition lock, you will have to disconect the battery for 3 min. Make sure you have the right key. Very important! Make sure the climate control is off before disconecting/conecting the battery.

SOURCE: 1999 Buick Park Ave Ultra Service Engine Light

The code PO742 indicates the torque converter clutch is stuck on.
The torque converter is what connects the engine to the transmission.
It engages and disengages according to signals from the pcm, to aid in
smooth shifting. There are a couple of things you can try. make sure trans. fluid is full, if thats ok check the 20 pin connector, located on left
side of car on top of transmission bell housing. Make sure there's no
corrosion or bent pins. If this clears the code your all set, if not you may
want to ask your mechanic and see what he/she recomends.
Hope this helps.
Good luck

SOURCE: 1998 Buick Park Ave with trouble code p0440

Trouble code p0440 may be a simple as an improperly replaced gas cap, or a crack in one of the evap hoses.
Have the code cleared, if it comes back, find a shop that will do a "smoke test" to find the bad evap hose, and have it replaced.