Weird electrical problem

subaru
electrical-wiring
impreza

#1

Please help!!! I have a 2004 Subaru Impreza WRX with manual transmission. Yesterday a strange thing started happening. I parked, I put the car in reverse gear, and removed the key. The radio turned off, the clock turned off… but the ENGINE stayed running!! The engine will cut off if I either 1) press the brake, or 2) put the gear in neutral. Now, picture this: engine is OFF, the key is still OUT, and the gear is in REVERSE… now, if I press the brake, the console display lights up (not the radio or clock, but the engine lamp, oil lamp, temperature lamp etc on the display console ALL light up, as if I had stuck the key inside and turned it halfway! When I let go of the brake, the display turns off. Oh, here is a kicker – I have an OEM GPS unit. when the car is moving forward, the GPS is fine. When I hold down the brake pedal, the GPS cursor starts moving BACKWARDS! Of note, the GPS is connected to the VSS wire from the vehicle computer. So, it seems like the speed sensor wire is sending a signal to the GPS that the car is moving backwards, when the brake pedal is pressed. I assume I have an electrical problem. Is this as simple as a faulty fuse? (I have not checked the fuses yet) Or is this a much more serious electrical issue? I am happy to provide other information as requested! Thank you!!!


#2

You could pull the GPS fuse and see if that makes any difference.


#3

Where would this GPS fuse be located? Also, would this resolve the issue of the engine still running when I remove the key?


#4

There is a wiring / ignition switch problem. You need a mechanic with electrical troubleshooting / rapair abilities. Not all mechanics fit this bill. Ask around.


#5

It sounds like the brake light wiring has crossed to the clearence lighting circuit. That causes the dash lights to turn on when you press the brakes. This issue is fairly common with bulbs that have the running and brake light filiments combined into one bulb. I think your model has seperate bulbs though so the problem won’t happen that way. You should have a trailer harness connection though in the rear so check that out for wet contacts.

Check the grounding to the car frame at the battery also. Make sure it is making good connection.


#6

OP if you have the lamps Cougar described (one bulb working as both a brake and parking light) I would replace both of those lights.


#7

Cougar and Joseph, thank you for your suggestions! As I am not too car savvy, I have a follow-up question, if you don’t mind! This bulb that you are referring to – are you speaking about the middle brake light on the back of the car? Or is this something else? Also, if I need to replace 2 different bulbs, where exactly are these 2 bulbs located? One other issue – Would all of this explain why my NAV system is receiving a signal that I am moving backwards while the brake is pressed?


#8

You’re welcome for the help. The bulb type we are refering to is normally located on the rear left and right sides of the car, not the middle light. Here is a link to site that shows you what the bulb looks like.

http://bulbster.com/lightbulbs/2057-p-2338.html?gclid=CLu--JvY4J8CFQwTawodfRZYWw

As I stated earlier, I don’t think your car has that type of bulb. The newer cars use just a single filament bulb so the dash light trouble can’t happen that way but you need to check the trailer harness connector for a problem since the brake and rear running lights are tied to it.

The GPS trouble may be caused by a problem with the shift selection switch for the transmission. Perhaps it has water in it. It is located on the transmission I believe. Since you state the shifter has to be in reverse for the dash lights to come on with the brake I suggest you have a shop check out that switch. You may need to replace it and doing that may solve all the trouble.

The fact that engine didn’t shut off with the ignition switch makes me think there has to be something wrong with the power wiring to the engine. You stated the radio and other things shut off like they should when you turned the key to OFF so it sounds like there may be something backfeeding power to the engine after the ignition switch. I assume the shifter has to be in reverse to make that happen and if so it points to that shifter switch again. By first finding out what is causing the engine to stay running while in reverse may lead to a common cause for all the trouble. I suspect the shifter switch is the culprit.

Update.
I did some checking on the wiring and it shows power from the ignition switch and the inhibit switch (shift selector switch) tie to the transmission control module. The inhibit switch just controls a ground connection to the proper mode selected. So checking the grounding to that area is important. The trouble may also be inside the transmission control module but before replacing it proper troubleshooting needs to be done to confirm that. Especially with the power to it.


#9

Cougar, these are excellent suggestions! I will check out the trailer harness today. If that’s not it, then I will take it to a shop and tell them your ideas. Your ideas make a lot of sense – we have had heavy rains recently, and my car has been outside in the driveway for most of that time. I will update you on my progress! THANKS AGAIN!


#10

You’re welcome fellow Soob owner. Check the update to my previous post if you haven’t seen it yet.

Before you take the car to the shop I suggest you print this thread out or give them something in print that states all things you have noticed about these problems since you have some very strange ones here. The more detailed you are about the symtoms of trouble the better it is for the tech. You did a good job on this post so using it should be sufficient.

Update.
After going over your post again I noticed that I didn’t understand correctly what you said about the dash warning lights turning on with the brake, though you stated it well. I was thinking the dash illumination lights were turning on, not the warning lights. That changes my thoughts some but I suppose the trailer harness could still be an issue though so checking it out would still be a good idea. This seems to indicate that power from the brake circuit is crossing to the ignition circuit. If the chassis grounding is bad and the trailer hitch connector is making contact to the chassis though some water that may be the path causing trouble.


#11

Cougar: It’s all fixed now, thanks to your direction! Here’s what happened – my NAV system is a Pioneer OEM system that I installed myself a couple years ago. The system is hooked up to the VSS wire (as I originally stated) and ALSO to the the wire on the “reverse/back-up” lamp on the rear passenger side, so the NAV computer knows initially whether it’s going forwards or backwards, and incorporates that with the satellite signal. So, I took a look in that area as you’d suggested, and LO AND BEHOLD!.. I found that the wires were completely frayed! I had not properly anchored them when I did the installation, so NAV wire to the “reverse/back-up” lamp was frayed, AND the wire to the BRAKE lamp was detached and frayed, and they were intertwining with one another! So, it looks like the brake was feeding the “reverse” wire, and this perfect storm led to all my problems! I reconnected the wires cleanly (and anchored them securely!) and now, everything is perfect! Thanks again for your advice, I would not have even thought to look back there if you has not chimed in! THANKS!


#12

Wow! Good job Suzy, thanks for the feedback and glad to hear you found the trouble. I didn’t think about that area (the radio connection) as a possible cause either. Whenever the original wiring is changed it becomes a good suspect for problems like this. Especially if the connections weren’t made correctly. Drive on happy Soob owner.