Will not start no matter what

Have you done a relearn on the pass-key?
GM PASS LOCK RELEARN- Ignition to "run" position, try to start and let key return to "run" position
Approx ten minutes security light will go off
Turn key "off" and wait 5 seconds
Repeat 2 more times for a total of 3 relearns.
Turn key off, then start it

Please check this out as well

It sounds like you've done some thorough diagnostic work on your 2000 GMC Jimmy. Since you've checked spark, fuel pressure, and even replaced the battery and starter, but the engine still won't start, it's a bit puzzling. Here are a few additional things to consider:

Compression: Have you checked the engine's compression? If there's a problem with compression in one or more cylinders, the engine might not start. Low compression can be caused by various issues such as worn piston rings, a blown head gasket, or valve problems.

Crankshaft Position Sensor: The crankshaft position sensor provides critical information to the engine control module (ECM) for timing and fuel injection. A faulty sensor can lead to a no-start condition.

Camshaft Position Sensor: Similar to the crankshaft position sensor, the camshaft position sensor also plays a role in timing and fuel injection. If it's malfunctioning, it can prevent the engine from starting.

Ignition Control Module (ICM): The ICM controls the ignition coil and can impact spark timing. A faulty ICM might lead to spark-related issues.

Security System: Some vehicles have anti-theft systems that can prevent the engine from starting. Check if there's a security light on the dashboard or if there's any indication that the security system might be activated.

Throttle Position Sensor (TPS): A malfunctioning TPS can impact the fuel delivery to the engine. If the ECM isn't getting the correct signal from the TPS, it might not provide fuel.

Wiring and Grounds: Inspect the wiring harness and grounds in the ignition and fuel delivery systems. Corroded or damaged wires can cause intermittent or no-start issues.

Exhaust Restrictions: A severely clogged catalytic converter or exhaust system can cause poor engine performance and starting problems.

That good, but his pressure is pretty good.