DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage.
DTC P0171 Fuel Trim System Lean
DTC P1406 Exhaust Gas Recirculation (EGR) Position Sensor Performance
how do i fix these failed codes... ps a month ago repaired upper and lower manifold gasket . car runs perfect even with some vaccume leaks .i need to replace more than one vaccume lines elbows.]

Now don't go spazzin' out on us...

Sorry that nobody replied to this one. I don't have much time right now, but I have a suggestion for you that will help to diagnose this later.

GET those vacuum leaks fixed!!!!

Before we can know what is really wrong with your car, you need to get all the vacuum lines replaced or at the least repair the cracked lines and fittings. Typically, it'* the rubber connectors, elbows, and the tee that fail.

To replace the straioght rubber connectors, get some rubber vacuum line (1 foot each of 7/32" and 9/32" I.D. line will do it. cutt the correct size tubing to match the lengths of the connectors and replace. Viola! Maybe 1/2 hour of your time.

Don't forget the connectors under your air intake box at the vacuum cannister!

As to the elbows and the "T", you will have to get those at your local dealer, but they should be fairly cheap even there. I think I paid about $3 for the "T". Give me a minute and I'll search here and get the part number for you.

OK, back fromn the search. The PN is 24502872 for the "T" and I paid $2.32 at a Pontiac dealer.


Just to sum up my response, until you get the vacuum issues resolved, your PCM may not return codes that tell you what really is happening. After replacing all the bad lines and connectors in your vacuum system, you may not get ANY more codes, though that may be just a bit too wishful.