Need some help troubleshooting a No Crank start problem.
2005 Mazda 3, 2.0L, base model, Manual Transmission, 180,000 Km

Prior to work on the vehicle, I disconnected the negative battery terminal and left it disconnected for two days.

After removing the throttle body, and intake manifold, I cleaned the intake manifold and throttle body, and replaced the PCV valve along with the rubber hose that connects it to the manifold. During this process, I also removed the injectors with the fuel rail as the intake manifold could not be removed otherwise.
I reassembled everything and double checked all my connections.

I have removed, cleaned, and reinstalled the throttle body in the past without any issues or starting problems. I have heard somewhere that the throttle plate should not be moved during cleaning. Inadvertently, I may have done this on this occasion. I don't believe i did but cannot tell for sure.

After reconnecting the battery, I turned the ignition switch ON, two click (accessories) and heard a whining noise, which I thought was the fuel pump pressurizing the system, but the noise did not stop after sometime and I turned the key to Start. The engine would not crank.
Turned the ignition key off and then back two clicks (accessories) and then heard a whining noise again. Turned out the noise was coming from the throttle body. Sounded like the throttle body motor wanted to move, but could not.

With the key left on, all of a sudden the horn starter blasting with the four way indicator light flashing. Appears the computer set an anti theft alarm. I disconnected the battery to shut it off.

Rechecked all my connections again and measured pins E and F on throttle body connector side (as per Mazda OEM manual). The resistance between E and F should be between 0.3 to 100 ohms. I measured 1.8 ohm with throttle plate closed.

Reconnected the throttle connector and attempted to start, but engine would not crank.
Checked for engine code and found non.
After turning the ignition off, as I approached the engine compartment, noticed that the throttle was fully open and then it would slowly close.

Hope someone on this forum has some experience or idea of what should be my next troubleshooting step.
Any help would be greatly appreciated.

Thanks, JimK

 

Problem resolved.

Very disappointed with this forum. Many views but no feedback. Perhaps I signed up to the wrong place.

Root cause of the problem was heavy corrosion at the starter solenoid push on spade connector. Shame on Mazda, as they did not use a bolted connection like most well engineered vehicles. The connection is exposed at the front of the engine bay where there is a lot of moisture. During my intake manifold removal/reinstall, I probable disturbed the connection enough to cause the problem.

On the plus side, it was a matter of time before this would have been a failure, stranding me away from home.