2005 GMC Envoy XL. Will not engage starter. Like something electrical. Turn key and nothing. Worked fine until now.

I wonder if the Immobilizer is related to the door locks and the fuse blowing broke the pairing. Try the reset

https://www.google.com/search?q=2005+GMC+Envoy+SLT+reset+security

..

Hello David..some GM vehicles have a feature called Twilight Sentinel which provides a couple of minutes of "headlight on" time after turning the vehicle off. (Check your owners manual for this features operating instructions.)

If your headlights never turn off, the failure is most likely in the headlight switch as headlights are wired hot...meaning you can turn them on without the key in ignition.

Probably a bad starter solenoid.Verify by probing the purple wire to the solenoid with a 12volt test light while someone turns the key.

Fix your car right away by clicking the link I attached
GMC Envoy 2002 to 2009 Service Workshop Repair manual

YOU HAVE TO REMOVE REAR STEERING GEAR CROSS MEMBER.REMOVE THE WIRE HARNESS FROM THE WIRE HARNESS RETAINING CLIPS ON THE TRANSMISSION OIL COOLER LINE BRACKET.REMOVE TRANSMISSION OIL COOLER LINE BRACKET BOLT.REMOVE RIGHT TRANSMISSION COVER BOLT.THEN REMOVE STARTER BOLTS THEN REMOVE STARTER.

1st, remove the positive lead to the abttery. Next disconnect the wires from the starter one at a time. I recomment you wrap each with a layer of black electrical tape to protect them. After the wring is removed, remove the bolts to any brackets that are attached to the starter and the two large bolts holding the starter into the transmission housing. Remove the starter. Reverse order to install new starter. Test before your close the hood. It isn't very difficult. If you run into problems, ask me, and I will assist you.

Hello,
I suggest checking your starter motor. If the starter motor is staying engaged it could be a bad solenoid or a bad ignition switch.

I hope this helps.

Roy

First, do not push the gas pedal at all when starting. There are many things that can cause a no start. A scan tool needs to be hooked up to see if there are any fault codes detected. This problem needs to be diagnosed by a trained mechanic.

Try disconnecting the battery for 10 -15 minutes. Make sure all functions are turned off first, such as HVAC (all switches CCW or off), radio off.

Mine did the same. It was a bad idler pulley