Weakn35s

Hi folks.
Having some electrical issues with my RX8. Engine was fine before, should not be related to that. I will be manual swapping my RX8 soon and would like to narrow down this issue before I rip apart the car again. If I can get it to start with my AT in, It will be so much easier to make the MT run properly. Also I know its cheaper to buy a MT but I will not for a reasons that include: 1) Doing this project to learn more about the car (A Hayasuba swap is desired for later) 2) this car was also my first car and means alot to me (I have other cars to DD so im fine) 3) good luck finding a MT S2 for a good price that had a responsible owner in my area. (I have waited 2 years for one, no luck)

Symptoms: Dash not illuminating numbers, Car clicks when attempting to start, does not crank or engage starter. Clock works, Accessories work (except radio which was removed) Key fob works, Headlights/Taillights work.

Cause of Death: Headlight cable frayed when it came in contact to tire, frayed wire came into contact with some metal in the car and fried something. This killed the dash, and radio, but the engine was running fine and the OBD2 port was giving me normal information (was using a diagnostic tool for that). Attempted to restart car and it never turned on again.
It has been 2 years.

Info from all Diagnoses:
1. Mazda Dealership: told me I had aftermarket alarm, said bad starter relay and dash relay (wtf is a dash relay) Tried to charge me 15K for a new wiring harness and dodged all questions I asked them (I left them asap)
2. Competent Shop: Aftermarket alarm was installed before (so that was true) Wiring harness was spliced into, ECU was tested and was fine. (Being here was getting expensive really fast so I had to leave after this)
3. Self Diagnosis Notes:
- Note security light does goes away with key inserted, car recognizes key fob (locks works etc)
- Check all accessories all work (radio was removed though)
- Can hear fuel pump work when key position is set to ON
- Replaced Battery (ik ik...) Did not work
- Replaced Starter fuse with 60a fuse, did not work
- Bypassed Starter fuse with a 60a charge, did not work
- Replaced Starter Relay twice, did not work
- Bypassed Stater relay by using wire to contact 30 and 87 sockets, Can hear clicking where relay is supposed to be, Starter still not engaging.
- Removed Starter, Tested and does work
- Inspected underside of fuse box, Wiring appears to be fine, have not used a Voltmeter yet since it is hard to lift the box without disconnecting power first.

What I think: Either Voltage is not reaching my starter due to shot wires, or the 12V input that is supplied from ignition to the starter is not coming to it. If that is the case Id have to look into ignition, Which is also going to suck since most info I could gather from forums only mentioned relay and starter.
Need some expert/experienced opinions on this. If I missed anything too please tell me.

Weakn35s

UPDATE: There is no signal coming from the ignition switch. I assume it is not the ignition switch because the car kept running after the electrical problems began. Might be the Immobilizer.

Becky245

I had some electrical issues with my 2009 S2. Pretty much everything on the car is managed by the PCM, so electrical problems start there, with the 5v reference. Something on the wiring has shorted out, either in the PCM or on the circuit. How to find it? You will need a complete wiring diagram of the PCM and which modules it controls. I found all the modules and tested for a 5v reference in each, the throttle position sensor didn't have the correct reading so I traced the color wire back to the PCM terminal and checked for continuity, and sure enough, there wasn't any. Cause of the short ??? Little critters got into my engine bay during the Covid lockdowns.
Unfortunately, there was evidence of bite marks in other places so I will have to check the entire harness visually!

Luckily I found the problem fairly quickly, fixed with some liquid tape, without doing the same test for grounds, which are through the PCM so will need careful scrutiny or the module will be fried! Shortly after my cooling fans disappeared and the car overheated, boiled out of the overflow, I was doing the 5v tests again and the grounding tests and inadvertently grounded the earth signal wire from the PCM to the cooling fans. PCM is now in hospital, getting open heart surgery, but the prognosis is not known. Then I will have to get it re-programmed once out of ICU! I'm looking for a way without going to the dealer.

Don't know if that helps with your issues, but my feeling now is to find a car electrics guru who understands fundamentals of ECU management and wiring.