So I have an electrical gremlin and I need a few starting points.

I will point out; this first post may be get very long while I give as much detail as I possibly can. I have scoured wiring diagrams (I have all of them) for my 99 and can’t seem to figure this one out.

I am having an issue with my turn signals and also reverse lights. The left side turn signal/taillight/stoplight seems to work fine, but the right side is where the issue is at.

So, long story short, I will just get into the details of what is happening. Sometimes, when I turn the turn signal to make a right turn, everything is OK. However, most of the time it is turned on, it blinks fine for a couple seconds and then flashes rapidly. When this happens, the taillight on the right side actually goes a bit dim and flashes rapidly. Also the left tail light will sometimes flash as well.

Next, when you put the car in reverse, the rear passenger reverse light does not come on with your foot on the brake. If you let off of the brake pedal the reverse light comes on. Drivers side reverse light functions as normal.
Also, when you open a passenger side door and the door pin comes out to trigger the dome lights, the dome lights come on very dim and the rear passenger taillight lights up very dim (I actually posted this a few months back thinking it was somewhat funny, but now it seems to be tied to other things and it’s not so funny anymore. Karma )

As I mentioned, I have looked over several things on wiring diagrams. It looks like Ground G402 ties a lot of these things together, but I don’t think a loose or rusty ground would cause this. To me it seems like a power wire from something is barely feeding some power through the ground possibly? Something just exposed somewhere?

Basic troubleshooting that has been done:
Multifunction switch was swapped (Had and extra)

Trailer harness removed (The wiring harness near the hitch was old and brittle. I don’t really tow anything so I removed the entire harness and module)

Replaced all of the taillight/stoplight/reverse light bulbs. (I had a pack of 10, so I removed all of them, cleaned the contacts and re-greased them as well)

Thought about replacing the stoplight switch on the brake pedal, but I have not done so yet. I don’t think that is what’s causing all of the issues.

Just looking for some places to start and what troubleshooting steps I should do from here. I have a multi-meter and test light as well. Something is definitely back feeding all the way through the multifunction switch. Just find it odd that the dome and interior light circuits are affected too.

Any help is greatly appreciated at this point.

 

Try checking the connectors shown in this pic. They're for the right tail lamp. You'll see from the pic what trim you have to remove.

 

Thanks for the pic.

I will probably pull both sides as well. I'm going to check ground G402 near the left tail lamp as well just to be safe.

I noticed on the wiring diagram that G403 says "Between Right Tail Lamp and Power Amplifier" I am assuming the the "Power Amplifier" is for the audio system if equipped. Mine does not have an amp. Is this ground right near the connector in your pic?

 

I don't think there is a G402, double check your diagrams and section 8W-90, Connector Locations.

"G403". You may mean G303 for the right tail lights.

There's conflicting descriptions as to where G303 is located. The '99 connector locations pics show it being with G302 on the left side rear. The 2000 XJ G303 location is shown under the passenger seat carpet. If the ground connections at the left rear look good, think about whether you have rusty floor boards in the passenger footwell (2000 XJ G303 location).

Here's a pic of the left side ground locations, behind the spare tire rack.

 

I think you are right on "G403" I think it was a misprint on the color diagrams I have. I checked the OE diagrams and it says 303. When I looked at the 8W-90 for the connectors, it said 303 was still "Between Right Tail Lamp and Power Amplifier." Weird?

Thinking back a couple months ago, I did have the passenger seat removed to fix some power seat wiring for the driver seat. Since the harness runs over the hump to the passenger side, I found a break under the passenger seat. I do recall some surface rust in the passenger floorboard area. No soft spots or anything, but definitely some build up. I can't remember how it actually looked under the seat.

Is the ground actually under the passenger seat, similar to the one on the driver side for the Airbag Module, or is more towards the front of the vehicle in the footwell area?

EDIT - My apologies for asking so many questions without checking. I'm at work to later this afternoon. Just trying to have a few points lined up that I can check when I'm out of here!

 

Let us know what you find.

Good luck.

 

You sir....are a gentleman and scholar.

I didn't get around to this the other day. Its been cold as hell here and I've been working late. When I went to leave the other day, the battery was dead. Apparently the cooling fan relay go stuck so it ran even when the ignition was off until the battery died. Didn't really feel like messing with anything after that.

However, last night I remembered I had made a bit more of a slit in the carpet on the rail that the seat sits on. I was able to feel the ground connection. I couldn't see anything and just had my hand under the seat. Connection was tight, wiggled it a bit. Then I wiggled the harness a bit. What do you know?! My dome lights started getting bright like they should. Reached back a bit further, and found a ring terminal that wasn't grounded still wrapped up in the wire loom.

Should be able to pull the seat out today and tighten it back up. Thanks again! If it you wouldn't have mentioned that ground possibly under the seat, I never would have thought to go back there. But once you did, it made perfect sense.

Much Appreciated

 

Here's a pic that shows the grounds under the passenger seat (2001 XJ FSM).

It shows G303. G306 is for heated/power seats. G306 the one not hooked up?

Once you do access the ground make sure there is no rust on the body connection and the wire ring terminal is corrosion free.

 

Looking at the diagram, I would say it is G306. It's more in the middle of the seat rail.

However, in that harness, I had two ring terminals that supply G306. One was hooked up, but the other was tied up (partially) in the wire loom. Once I felt it, I touched the ring terminal to the floor pan and everything acted normal.

I can't really remember seeing G303. I'm pretty sure I would have to remove the seat as it looks like it would be outside of the front right seat bolt but before the door sill plate.

I will give it a double check when I pull the seat out today to tidy everything up. But, it does appear there are two ring terminals that connect to the G306 location. At least from what I can feel under the seat. The ground terminal that is not connected is somewhat short. I will have to move the harness forward a bit to get it to connect to the G306 location.

I'll try and snap a pic when I have seat out.