20 Most Recent 2005 Pontiac Grand Prix - Page 8 Questions & Answers

The antitheft picture/icon is a visual indication that something in the car's antitheft system is failing. In most GM cars and trucks there is a hidden system that most people are unaware even exists. From the moment you put your key in the ignition, there begins a constant line of communication between your key's security chip or transponder, to the ignition's lock cylinder, and then to the car's TDM (Theft Deterrent Module). These 3 parts are in CONSTANT communication. If the key is in the ignition, then these parts are sending signals to each other. The security light illuminates when that signal gets broken, even just for a second. When the signal breaks, the car misinterprets this as an attempt at theft and goes into antitheft mode. The car thinks its being stolen or hotwired because it is not getting that signal from YOUR specific key. This is why the security light turns on and shuts down your vehicle. This link explains it pretty well. http://vatspasslockpasskeysecurityhelp.yolasite.com/

Here is the trouble tree for that code it is most likely a bad cat but follow the trouble tree to see where it lead's you.
DTC P0420 or P0430

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection\Initial Inspection and Diagnostic Overview\Diagnostic Starting Point - Vehicle
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0420

* Catalyst System Low Efficiency Bank 1

Important: A new converter with less than 100 miles on it may set DTC P0420 or P0430 due to out-******* of the internal matting. Operating the vehicle at highway speeds for approximately 1 hour may correct the condition. Hope this helps

A bent wheel, a lost wheelweight, loose lugnuts, front end misalignment or any of a dozen other serious problems. Take it to an alignment shop, NOW, before you do need a new tire.

hope it helps

There are several things that may cause those issues - and they are all potentially dangerous ( and labor intensive )!!There could be a bad ground point, burnt or pinched wire, bad relay, poor /corroded connection to the computer, etc. I'm sorry, but this is something that requires a hands on by a knowledgeable technician! Sorry for the bad news, and thanks for using Fixya!!

Not sure about the grinding noise but swaying could mean bad shocks/struts.

SUSPENSION ARM.IS WHAT ITS CALLED.

Remove the cap under ignition push button i use a toothpick key wil come out

find the bleed valve on coolant system and burp it. make sure you are using a good 50/50 mix of coolant. maybe run a coolant system cleaner . maybe a clog? if worst come to worst blow head gasket

the temp gauge works of a different sender to the coolant sensor. IT has 1 wire only and changes resistance as the water heats up there by moving the needle on the gauge up the scale Check that the wire is tight on the sender unit and if so then replace the sender unit.. The difficulty in re starting the motor may be because it is over heating but you would not know this because of the faulty sender unit.

I would try to clean out the egr valve , check for leaks at the evap canister, check the evap canister soleniod , and lastly change out the cat convertor, The cat convertor is most likely under the federal emmission warranty of 8 yrs,.80000 miles. You can take the vehicle in to have checked by local dealer or call gm customer service to check the warranty on the cat. convertor by giving them your vehicle number.

Make shure the steering pump has fluid and that your front tires are not low