I am looking for help diagnosing my 06 350z. The car started backfiring and the passenger side cylinders weren't responding then it just turned off after driving to the mechanic. The car just stutters but doesnt turn on. It initially burned 3-4 coils when it was on and now still burns the first coil on the passenger side when key is in the on position. There is also a fuse that constantly blows on the fuse box by the drivers feet. Cant pull any codes with obd2 or other reader. When testing for spark, it was fairly weak and inconsistent. and i think the gas pump isn't engaging now either although it was, maybe it does on some tries and doesnt on others.(gas pump isnt the issue)

A bit of background:
The car got crashed into the right side front wheel and was dented pretty significantly. I had it in my driveway for about two months and I would turn it on to make sure it was still working every now and then. Once I finally decided to send it to get fixed, the problems started. The mechanic took about three months and all i wanted was the dent pulled. It also had a coolant leak that I planned on fixing on my own. He decided to "fix" the leak too and had to move around tubes and wiring to get to the leak. He the reconnected everything by just eyeballing it and guessing where stuff went. Im not sure is this is where it all went wrong as he might've broken something or connected something bad. He didnt even ground the wires that were previously grounded and Im not sure if it needed more now. Another thing could maybe be how they welded in the area they pulled back in place since its near the battery and fuses. He said maybe the fuse box just got damaged by the hit, but what abt the other issues? He might've also done something wrong when connecting the computer to pull codes and locked my car. I have no idea what Im doing now or how to diagnose it and just wonder if anyone out there can help.

 

Depending on the severity and exact location of the collision damage, it's very possible the fuse box and/or wiring harness was damaged. It's also very possible the body shop introduced more problems, but I would lean more towards the collision causing the wiring faults.

If it was my car, I would closely inspect all harnesses that fish through the engine bay on the passenger side. It's pretty easy to follow as it exits the battery compartment along the fender and then snakes down behind the headlight. This would be my starting point as it's closest to the accident damage you described.

If you're busting fuses, you have shorts. You should leave the battery disconnected until the source of the short can be located. Further attempts to test spark or start the car could cause permanent damage to the ECU's ignition system circuitry (if not already damaged).

You're going to need a copy of the FSM wiring diagrams and time to familiarize yourself with how to read and trace said diagrams. You're also going to need a multimeter and a wiring probe kit to check continuity and shorts to ground. You might get lucky and find obvious damage to the harness, if it's not serious you might be able to patch/repair the damage with some solder and weatherproof heatshrink. The FSM can be downloaded from Niccoclub among other places on the net. The process to inspect all the connectors/pins is very time consuming, start in a focused location and branch out from there. The wiring diagrams and harness connector locations are all available in the FSM, but might be spread across multiple chapters of the manual. You're going to need to take meticulous notes on wire colors, pin numbers, starting and termination points, and harness plug names & locations on the car. I would do this 1st before starting any kind of wire probing.

Grounds could also be damaged, and there are two major chassis ground connections on the passenger side. One is directly behind the headlight on the wheel house. The other is down lower, on the frame rail, near the coolant reservoir tank.

Don't fire the parts canon until you've confirmed the wiring faults have been resolved. Throwing a new ECU or IPDM at it now would just be a waste of money.

If this sounds like more than you can tackle, then taking it to a professional may be your best option.
Good Luck!
-Icer

 

Helluva first post from the OP. Icer has put together a sensible plan in his post, and note that last sentence about getting some pro help (not the shop originally hired). Having had Z electrical problems in the past, I know how difficult they can be, Good luck!