2006 monte carlo wont crank
 

new battery, new starter, no security light or codes ? would appreciate any ideas

By won't crank , do you mean it won't even spin over? Or will it spin over but just not fire up?

does not crank ; motor is free;

I think Aerocoupe is asking if does anything at all when you turn the key to ignition position. Does the motor turn over and not fire, or nothing at all. Can you hear the starter or solenoid spin?

when you turn the key you hear a single click - sounds like solenoid engaging but starter motor does not spin; bench tested new starter & all good

Sounds like a VAT issue. Somewhere in the chain of communication between the chip in the ignition lock cylinder, BCM and PCM communication is getting lost. Those three component store and exchange a numeric code and if it isn't recognized by all parties the engine will not start. If you have a code reader see if anything comes up.

First try doing a security system re-learn procedure. Perhaps that will reset everything. If it doesn't you've only lost the time it takes to try it.

This procedure allows the PCM to function properly in your vehicle after a Battery disconnect or a Security Breach.
Follow the steps listed below completely.

1. Attempt to start the car by turning the key to the Start/Run Position.
2. Observe that the vehicle fails to start and that the security light is illuminated.
3. Release key to the 'ON/Accessory' Position. (DO NOT turn key to the 'off' position, DO NOT remove the key.)
4. Allow the vehicle to sit with the key in the 'ON/Accessory' Position for no less than 11 minutes (the security light should stop flashing, if not wait up to 3 more minutes).
5. Turn key to off position and allow the vehicle to remain in the 'OFF' position for no less than 30 seconds.
6. Repeat #1 - #5 for 3 cycles.
7. On 4th-5th attempt, car should start.

NOTE : Since this is a fairly long procedure, I would limit all electrical sources, such as disconnecting headlights, to prevent discharge of battery.

NOTE 2 : It is SAFE to wait LONGER than the allotted time, but it is not safe to wait less time. I.e. 12 minutes instead of 11 minutes should be safe; however, waiting 10 minutes instead of 11 minutes is not safe.

Properly executed, this procedure should take approximately 35 minutes to complete.
If that doesn't work verify engine grounds are clean and tight.

If that fails you likely have a problem with either the ignition lock cylinder which contains a chip, or the ignition switch housing. There is also the possibility of a bad BCM or PCM but less likely.

Please keep us posted.

thanks for all the help-will definitely keep u posted;tried a vat reset even though no security light, but was very different from what u just advised and did not help;

You probably tried the 10 minute re-learn procedure which sometimes works too. The 35 minute procedure might not work either since there's no security light. VAT failures have a whole lot of different symptoms so it's worth a try before you start replacing parts.

security system reset did not work; on to ground, bcm,pcm,ignition lock cylinder/switch housing