When starting it cold, it starts then stalls. Then repeats this process three time and then stops. It works fine if the key is in the ignition as well as when it is warm. Any thoughts?

30 minute reset turn key on ten minutes security light will go off turn off back on three times it ctanks

idle control sensor might be able to be cleaned

could be a fault
or adjustment required to neutral safety switch

surprised there is no check engine light for fault codes

Before you start it cold, prime the fuel pump twice or three times. Lets make sure you have adequate pressure.

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According to RepairPal: "the car wont start due to anti-theft system, it will say wait three minutes then start, but repeat this process 4-5 times - Visitor"

They say there are 75 reports of: "Problems with the anti-theft systems using the raised-chip key can prevent the car from starting. The wires in the steering column to the ignition lock cylinder tend to break. The the key and ignition lock cylinder must be replaced to correct this condition."

You can get a free wiring diagram and fusebox layouts at Autozone.com. Just register your truck on their site.

If you look at the wiring diagrams you should see that the starter lockouts and shift interlock is a separate process. Neutral is a position which allows the starter to work.

What you are having problems with is the RUN circuit on the ignition side. You could have a bad ignition switch. The switch should have an Ignition Relay in the Powerbox. If this is the Diesel, they have a KILL circuit to stop the engine that is different than a gas engine since the Diesel fires by compression.

So looking at your wiring diagram, you would be looking for a connector or component which could cut out intermittently. I am thinking more of a Relay because you have to reengerize the circuit by turning the ignition switch to OFF, before going to CRANK, and then RUN. Most of the time, the starter interlock only controls the start circuit.

Another possibility is the Antitheft. If the KEYreader loses communication with the Security system, it may stall. I know that vehicles will not start without the correct key or if an unprogrammed Blank is inserted.

I hope my solution helps.

if the security light is blinking.... turn key on try to start truck let the key go and it should leave all the dash lights on wait about 10 minutes til the security light goes off then turn the key off and then try to start the truck again repeating the process three times . no more than three. on the last time the security light goes off turn the switch off and it should start the process is called the ''10 minute relearn''.

Fill in the fuel, switch on the ignition key, wait for 5 seconds, switch off the key. Repeat the process for three times and start the engine.

Coolant temperature sensor can be checked with an ohmeter.
You should be able to get the cold and hot values from your local auto parts store or a GM manual at your library.
Good place to start with the described condition .
Have you replaced the coolant lately or therm ostat?
If so it may have an air pocket.
To check this feel if you get hot air from the heater constantly or it fluctuates.

You probably need to do the relearn process to reteach your ECM or PCM . dont try to start it but turn the key on for 10 mins until all the idiot lights go off, turn the key to off for 5 seconds and repeat the process 2 more times for a total of 3 cycles. It should be fine after that. I am no expert but it worked for mine.

Turn the ignition to run. Within three seconds push the gas pedal to the floor three times. Turn the key to off, and then start the car. The light should flash three times signifying that it reset. If it does not, try repeating the process, but instead of turning it to off after stepping on the pedal, just start the car.