No Start Electrical Problem
 

I have an electrical problem that I can't resolve. My 1999 Boxster will not start. Initially, it would take 1 or 2 twists of the key before the starter would engage. This went on for 6 months or so. But then the problem got worse, and now the starter will not engage at all. There are other weird symptoms:

• Putting the transmission in Reverse causes everything to turn off
• Depressing the brake pedal causes everything to turn off
• The ignition switch has been replaced
• Warning lights on dash will flicker when key is turned on
• Trip computer display items (bottom of center gauge) will cycle on its own (as if a button is being pushed)
• This wasn't an all-at-once problem, it got worse over time and more weird things started happening
• The battery tested fine and is on a charger. I checked the voltage while cycling the key and it never drops below 12.6 volts.
• Here's a short video clip of the problem: https://www.youtube.com/watch?v=NjepE0EzxT0

Any ideas? The main ECU in the rear trunk?

Problem details updated. I'm going to look through the wiring diagrams to see if any of these symptoms point to a single source of failure.

Disconnect the reverse light switch connector? It is shorted to ground?
Ditto brake light switch . Or remove the relevant fuses?
clutch interlock switch
Meanwhile ,do all the usual culprits - corroded battery cable inside the insulation? The infamous "Y" connector harness ,etc. Been covered many times.

search and look up ignition switch issues

The other thing I would look at is grounds. Bad ground will do that as not only power important but grounds. Look up where the grounds on your car are located. remove clean. and reattach them. Sounds like there are not enough grounds to go around

just looking at the video says bad ground somewhere, what did you do just prior to the issues?

Thanks, looking into ground issues. I have a copy of the wiring diagram that should help narrow it down.

I didn't do any type of service or repair prior to this problem surfacing. . . it surfaced all on it's own. It quickly progressed from flickering lights on the dash to the weird problem with the brake/reverse lights.

I would start checking with the main connections first and making sure they are solid. Start with the battery, both positive and negative actually removing, cleaning and re installing the cables BOTH ENDS. This will mean removing the cover and making sure the positive post is secure AND the ground strap from the engine is secure to the frame on both ends. From there I would check the plug in at the ignition switch and then the individual grounds threw out the car. Next main grounds are under the drivers seat for the immobilizer, but make sure the battery is disconnected when checking this because if you remove the seat with the battery connected the SRS light canl pop up and you cannot erase without the proper tool. This ground is important so do not skip.

Check the other grounds and look in the manual for the locations.

Of course I'm assuming a lot has been already checked as I have not seen the car. That the ignition switch is actually good, that the fuses are all good, that here is a good strong battery, etc.

I had a similar problem and replaced the sending unit, but in my case it was only that. Get a qualified Porsche electrician. Good luck

I spent more time diagnosing today. First of all, here's a more representative video of the problem. The engine is running, but the gauges are going crazy:
https://www.youtube.com/watch?v=t4urfxNYUiA


I started by checking the ground points in the front and rear trunk, and they looked perfect. I then decided to wade through my wiring diagram book to look for common ground and/or power sources for the various issues (gauges, dash, reverse light, brake light, cruise control, starter/key switch.) After about an hour of flipping between pages, I couldn't find any commonalities.

So I decided to take a different tact by removing the fuses for the problem components. Dash lights, reverse lights, brake lights did address the issue. But when I removed the fuse for the the gauges, it started immediately every time. Brakes and reverse lights started functioning properly as well. So the cause of the problem seems to be related to the gauge cluster causing electrical problems for other systems.