lonewolf9

I noticed today that my engine compartment light isn't working. I popped out the fixture thinking it was the bulb. I looked at the bulb and it appeared good. So I connected it to the frunk light and it came on quickly. So the bulb is good. But when took it back to the engine bay connector it won't light.

I test voltage at the connector and it read 1.95V which I think is low.

Any ideas?

Thanks!

DC911S

Check for fuses? Any other lights out? Defective switch?

yvesvidal

The trunk light is controlled by the rear module. It will shut off automatically after 2 hours of being open.

I would check the Fuse to the rear module, the ground to the bulb and the trunk lid switch.
You could try to reset the rear module if you have access to a Durametric cable.

Yves

lonewolf9

Thanks, Yves. By rear module do you mean the rear control unit? I found that and the fuse there is good. I'm not sure what other fuses to check. I'm looking at the fuse diagram under the How-To section and nothing there indicates rear engine light.

I also checked ground by taking one lead of my multi-meter to the connector and touching the other to the chassis. I got continuity that way. Funny thing is, I got continuity to the chassis by touching either pos. or neg. connector.

Thanks.

Ericson38

Did you loose battery power to the car (or change the battery) recently ? This happened to mine, along with loss of heated seats, after extended time with no battery. Had to get dealer to reset via Durametric.

lonewolf9

Not that I know of. But I haven't had the car very long. When I get a chance I will check the heated seats. Not much of a need for them now. (AZ is hitting record heat).

If I end up taking it to the dealer, any idea how much they charge for something like that?

Thanks.

JAGMAN1

It should read 12V at the connector. Beyond that try to find a way to measure the voltage on the wires forward of where they bend at the rear lid hinge. That will help you trace a short in the wire. If you can find where the wires plug into the rear module that would be best.

karl1672

Bringing this one back - I went to replace my interior lights with LEDs and noticed that my engine compartment one wouldn't come on (not a polarity issue). Rear control fuse is fine,
I measured 5.5V across the connector and 12V when I go from the hot side of the connector to a good ground. So, appears to be a weak ground issue. I can easily tap in to a good ground, but since I don't have a wiring diagram, not sure if there may be any implications - which I doubt. Any thoughts? My other option is to forget about it since a flash light would work just as well

lonewolf9

Karl, I would concur with your findings. The voltage for me was much lower, except when I connected a good ground. So perhaps there is a weak/bad ground issue on the light for these cars. I have not been able to find a wiring diagram, so I'm not sure where it goes.

karl1672

Thanks, I just spliced a new ground inline with the existing one, figured it couldn't hurt. Hate hacking the wiring, but at least the light works - fortunately a relatively trivial issue

lonewolf9

That's clever. Can you tell me what you grounded it to?

karl1672

Sure. I spliced a new wire onto the original ground wire and used a ring terminal on the fan mounting bolt closet to the light. Probably not the best ground, but close and did the trick. Shrink-wrapped everything and followed the factory routing so it doesn't stick out too much

lonewolf9

Very nicely done! Thank you for sharing. I would like tackle this on my own car one day.

karl1672

Thanks

funnelofdoom

So I did some studying, and the engine compartment light is actually actuated by a ground signal from the rear control module. The 12V wire is always hot because it is on a timed circuit like many of the interior lights and gives the car two ways to shut it off (timer or discrete control). So you're not fixing a bad ground, you're just forcing it on all the time if you rewire the ground.

I was fixing some bad rear module wiring done by the previous owner in which they had wired it incorrectly and I figured that was the problem (possibly when they replaced seats and ripped a bunch of wiring from the original harness). While rewiring correctly did not enable the engine light when I opened the lid, I was now able to turn the light on via my Foxwell NT530 diagnostic section which indicates the module and wiring themselves are perfectly fine.

If you're having the same issue, it seems to be a problem with the programming of the module. I went to my Foxwell coding section in the electrical module (last one) and there is an option to activate/inactive the rear eng. comp. light. However, the only option I get is "inactive". I tried opening it via the Cayman/Boxster module on the Foxwell and I get the same thing. I think there is some problem with replacement rear control modules (mine was replaced at some point) in which they're not being programmed correctly. I checked on the Durametric video for the 997, and there is not even a coding section for the electrical module (not sure if this is a separate module or if it's just part of the front module).