I looked at the relays again, loosened off the main ground off the battery, cleaned and replaced. I pulled the crank relay and linked 30 and 87, the starter turned the engine over so that's good. I tried pushing every plug I could see to check nothing had come loose. I removed the radio and looked for any bad wiring, all looked good. Still not starting !!! The thing that puzzles me is the Power Steering and Traction control warnings after I've tried to start it

 

New battery means nothing, you should have it load tested.

Why did you put a new battery in? Was it dead? Maybe the alternator is on it's way out, which killed your old battery. Or maybe the old battery tried to kill the alternator.

 

Tried checking the neutral safety switch ? (I'm assuming it's an automatic trans)

 

How is the fuse box halves investigation going?

 

When I first broke down the AAA guy did a battery test it was fine. Where
abouts is the neutral safety switch

 

Top of the transmission

 

The fact that you could bypass the relay means that the BCM is not sending a start signal
The power steering and TC are warning because they are not getting power.
What did the AAA guy touch under the hood?
Check fuse #10 on the BCM.
Check all of the wires around the BCM for evidence of splicing, after market immobilizers splice into some of them.

Have you checked for codes? There are many that don't light the CEL. Is the security light on?

How about remote start? If it is turned on in the DIC Lock, Lock + Panic on any fob works.

Not supposed to matter but the hood ajar switch could be at fault. It is 2 switches if you unplug it and ground the pink wire the switch is bypassed.
You might try the key learn procedure outlined in the Owner Manual. If you have any transponders on your keyring take them off.

Others have had the same problem but never came back to let us know the fix.

 

Oh, there's a thought... Is the hood closed?

 

That should only matter with RVS, but needs to be ruled out.

An experiment to see if the TDM is doing it:

turn the key to run
start engine by jumping the relay
if it runs the TDM is reading the key and sending the fuel continue signal.

Another 3:30 AM thought is the switch itself may be bad. It is one wire the start position sends a 5V signal via a 1.8K resister,

Earlier I said it is the BCM that sends the start signal, that is incorrect it is the ECM. Which adds another thought; lately there have been reports of oil migrating up the wire harness to the ECM and fouling the connections.

Here is the pertinent part of the wiring diagram. The purplewhite wire carries the start signal to the relay, the dark green wire is from the park/neutral sensor. on start the white black should be less than 5V , in ACC or run it should be 5V.

 

Thanks again guys. I'll try and check this out later this week. Luckily I have my work van to ride around in until I get time to do the HHR