I need to route some wires from the cab into the engine compartment. I thought that would be easy. But, I'm trying not to mess anything up.
In the cab up against the firewall is some kind of plastic cover so it's hard to see where to drill a hole. I see where the wiring-harness goes through but it doesn't look like I could shove an extra wire through, its all pretty tight and goes into a plastic hose in the engine compartment.

Where is the best place to shove a wire through from cab to engine compartment? Or, do I realy need to drill a hole? If so where is the best place to drill?

4th gen, 98 Camaro.

 

4th Gen FAQ 10th question from the top.

 

I'll keep that in mind, but I'd rather not move the PCM.
Anyone else?

 

You don't have to move it permanently, it takes about 30 seconds, 4 bolts. Lift it up and move it out the way, push your wires through, and then bolt it back down, if it takes you more then 10 minutes you are doing something wrong.

 

Push the wire through the grommet from the cabin and you can pull it without moving the PCM. Although it's easier if you move it, if you have "monkey arms & hands" like me you can reach down there without moving the PCM. You will get cut up if you're not careful though by the edge right below the windshield wipers. I got it done without moving the PCM, but I got my arm cut up doing it. I probably could've avoided that if I'd been more careful. Whatever you do, you shouldn't be drilling holes in the firewall. Just run it through the grommet on the passenger side. I cut a hole just big enough to fit through my power wire (4 gauge) but try to seal it against moisture if you can.

Abe

 

Well, I didn't want to route through the passenger side because my wires would then have to go back over the engine to the drivers side. On my car, the drivers side has a nice auxillary positive battery connection, as well as all the fuses, and some space to put things like extra relays.
Also, I didn't want to mess with the PCM on the passenger side because I read where one guy had problems after that, yikes. Plus, I plan on putting a few more wires through when I install an alarm.

So, I drilled a hole just above the big electrical connector on the drivers firewall. I put the hole one inch above the top screw of the connector underneath. There is plenty of room there. I just drilled right through the plastic firewall cover. It took two different drills and a Dremal because of the strange angle I had to drill. When I was done I put in a grommet and then ran a small piece of hose through the grommet. It fit really tight. I used the hose so that it pointed down in the engine compartment. It's such a small hose and grommet I'm sure no water could get through. On the firewall side I used a split electrical cover to take the wire to the fuse block area.

Anyway, it's OK to drill a hole in the drivers side. It works real good and leaves you room to grow.

 

I don't recommend using that connection. The cable between it and the battery is undersized for most car audio applications. You're better off connecting directly to the battery using a side post adapter. Just make sure you test fit it first. I had one that would bottom out in the battery terminal. I ended up cracking the battery casing in my Tahoe when I torqued it down. This caused acid to leak out and corrode the connection and battery tray. I ended up using my bench grinder to shorten the adapter post.

Whoever "had a problem " with their PCM must have been a moron. The procedure couldn't be any easier.

If you insist on using the aux. connection I would recommend replacing the cable between it and the battery with a section of 4awg power cable.

 

LS1 RULZ:
I hadn't thought of that. But I'm not much of an audiophile so I won't be installing amps and such. I just needed an easy connection for my fog-relay and fog lights. The cable on the auxillary looks big enough for just those two things. But I will think about upgrading it to a bigger wire.

 

I fit my amp kit wiring through the firewall with no modifications...

 

samault: Yeah, well, if it works it works. I would rather not drill on my car, but that's just my preference. I was also thinking about drilling a big hole for an amp power wire, not a smaller hole you'd need for the wiring you're most likely using. And don't be afraid to move your PCM, if you're wiring up extra accessories and drilling holes in your car you're already doing things much more complicated than moving your PCM. And like the White Rascal said, be very careful with those side post battery adapter things. I had to use about 4 or 5 washers to get it to snug down without breaking the battery case. Damn I hate these side-post batteries. And if you ever do need to go from the passenger side firewall grommet to the driver's side, it's very easy to thread a wire under/behind the center console as long as the wire has enough length.

Abe