Dome door courtesy issue

[Green2000LX]

The previous owner had an aftermarket led that was about 1/4” over sized in the center and incandescents for the side 2!? Ive been driving it like that for a few years now. I wanted to changed them
I was trying to make them all led.

After I replaced the side 2 to led, with the switch set to door it would be very dim. Light works normally when switch is on.

Of course I had to start monkeying around with it to see if I could fix it quickly shoulda unhooked the battery!
I’ll admit I caused an arc when trying to fix the tabs while still hooked up, ugh!

I somehow shorted the green wire that powers the light when the doors are open?

When I read it with my meter I get .004 voltage on the door setting I get 12.4 when on.

Any ideas where to check next? I really don’t wanna pull my headliner down! I never use the feature but of course now it’s not working I need it lol
I definitely have shorts in the driver door jamb loom I need to get around to.

Thanks

 

[Green2000LX]

The previous owner had an aftermarket led that was about 1/4” over sized in the center and incandescents for the side 2!? Ive been driving it like that for a few years now. I wanted to changed them
I was trying to make them all led.

After I replaced the side 2 to led, with the switch set to door it would be very dim. Light works normally when switch is on.

Of course I had to start monkeying around with it to see if I could fix it quickly shoulda unhooked the battery!
I’ll admit I caused an arc when trying to fix the tabs while still hooked up, ugh!

I somehow shorted the green wire that powers the light when the doors are open?

When I read it with my meter I get .004 voltage on the door setting I get 12.4 when on.

Any ideas where to check next? I really don’t wanna pull my headliner down! I never use the feature but of course now it’s not working I need it lol
I definitely have shorts in the driver door jamb loom I need to get around to.

Thanks

View attachment 4120104

View attachment 4120105

View attachment 4120106I couldn’t find the oversized bulb for the previous owner but it was a little bigger than the one on the right the left is the oem Toshiba light

 

[asmara]

There will almost always be a small amount of current leakage in these circuits. The problem you're seeing is that your replacement LED lights up too easily—it takes very little current to make an LED glow. This is normal behavior in a system that was originally designed for incandescent bulbs, which need much more current to light up.

You have a few options (and don't need to pull the headliner). 1) Live with it. If it's just a faint glow, many people simply ignore it. 2) Try a different LED bulb or use an incandescent bulb. Some LEDs require slightly more current to light, and bulbs marketed as CANBUS or anti-ghosting often include built-in resistors to prevent this issue. 3) Add a resistor in parallel with the bulb. This gives the leakage current somewhere else to go, so there isn’t enough left to light the LED. This is the only fix if you want to keep the current bulb but get rid of the glow.

The arcing didn't do anything if it didn't blow the fuse.

 

[Green2000LX]

There will almost always be a small amount of current leakage in these circuits. The problem you're seeing is that your replacement LED lights up too easily—it takes very little current to make an LED glow. This is normal behavior in a system that was originally designed for incandescent bulbs, which need much more current to light up.

You have a few options (and don't need to pull the headliner). 1) Live with it. If it's just a faint glow, many people simply ignore it. 2) Try a different LED bulb or use an incandescent bulb. Some LEDs require slightly more current to light, and bulbs marketed as CANBUS or anti-ghosting often include built-in resistors to prevent this issue. 3) Add a resistor in parallel with the bulb. This gives the leakage current somewhere else to go, so there isn’t enough left to light the LED. This is the only fix if you want to keep the current bulb but get rid of the glow.

The arcing didn't do anything if it didn't blow the fuse.

Interestingly the light would come on with the door before I started changing bulbs it.

I did blow 2 10a fuses for the interior lighting while fiddling with the center light (one that needed the tabs realigned. I have tried putting incandescents back in but nothing. Would the two side lights that got changed to led be the issue?

The trunk light switch works with on and the door function. I was going to try to tap into that wire but it only works with the back doors.

I mean it does make sense that the light that I changed messed with the circuit as well. The diagram seems to indicate that the door circuit goes through one of the other lights?

I’m going to follow that wire back to the D/S kick panel and see the reading I get. I have a D/S kick panel on hand if I need to swap that out mine does have some water damage.

It’s so puzzling I’m not sure how that wire got damaged I’m suspecting it’s the wire since the rear circuit if fine?

I’m hoping I didn’t damage my ecu? That’s where this signal is coming from.

 

[asmara]

Interestingly the light would come on with the door before I started changing bulbs it.

I did blow 2 10a fuses for the interior lighting while fiddling with the center light (one that needed the tabs realigned. I have tried putting incandescents back in but nothing. Would the two side lights that got changed to led be the issue?

The trunk light switch works with on and the door function. I was going to try to tap into that wire but it only works with the back doors.

I mean it does make sense that the light that I changed messed with the circuit as well. The diagram seems to indicate that the door circuit goes through one of the other lights?

I’m going to follow that wire back to the D/S kick panel and see the reading I get. I have a D/S kick panel on hand if I need to swap that out mine does have some water damage.

It’s so puzzling I’m not sure how that wire got damaged I’m suspecting it’s the wire since the rear circuit if fine?

I’m hoping I didn’t damage my ecu? That’s where this signal is coming from.

You could have fried the instrument ECU (it's above the radio). I had to replace mine when I bought it because somebody fried it, and the dome light wouldn't go off because it thought a door was always open. I did A LOT of wire tracing before determining it was the ECU. One thing I recall from my issues, the trunk dome light is triggered separately.

I would check everything before you look at replacing the ECU. Even though mine was fried, they are typically pretty hardy. File this away, but if you have to replace it, there are a bunch that seem to be interchangeable (I posted some numbers somewhere in the forum). I couldn't find mine anywhere, and a local scrapper let me try a later model one. It works fine (and is still there).

First thing, just to make sure you understand how this works - It is a negative switch circuit. That means the hot is always hot (red wire in this case) and when you want the light to go on, either the switch itself or the system connects the circuit to ground. When you move the switch to 'on' or use the other two lights, you are connecting the negative side of the bulb to ground (W-B). When you open a door, the ECU senses it (actually the door switch grounds itself) and then the ECU grounds the G-W wire.

I'm not seeing in the diagrams you posted where the wiring goes through another light. The G-W wire goes directly from the dome light to the driver's side fuse/junction box (connector 2A, pin 3), then to connector 2P, pin 60 (that's the one on the side with all the SB wires), and finally to the instrument ECU. You could put the dome light into door mode, unplug 2A (just to be safe), and short pin 3 in 2A to ground. The dome light should light up.

You mentioned the other two lights. According to the diagram, all three lights use the same hot (red) and ground (W-B) when turned to 'on' so they should all work if you have voltage and that ground is good. It likely won't matter for those bulbs if they are LED since there is a physical disconnect when they are off (ie they shouldn't glow). Also don't forget that LED bulbs typically have polarity. That means if they don't work one way, you flip them around.

Finally, you can put your multimeter in continuity mode and check from the green wire in the dome light to 2A pin3, then 2P pin 60 and then at the junction ECU Connector A pin 2. If you have continuity the whole way, then the ECU probably went down.

Oh, one other thought. Does your door ajar light up when the driver's door is open? What about the passenger door? If not, then you might have ECU troubles.

 

[Green2000LX]

You could have fried the instrument ECU (it's above the radio). I had to replace mine when I bought it because somebody fried it, and the dome light wouldn't go off because it thought a door was always open. I did A LOT of wire tracing before determining it was the ECU. One thing I recall from my issues, the trunk dome light is triggered separately.

I would check everything before you look at replacing the ECU. Even though mine was fried, they are typically pretty hardy. File this away, but if you have to replace it, there are a bunch that seem to be interchangeable (I posted some numbers somewhere in the forum). I couldn't find mine anywhere, and a local scrapper let me try a later model one. It works fine (and is still there).

First thing, just to make sure you understand how this works - It is a negative switch circuit. That means the hot is always hot (red wire in this case) and when you want the light to go on, either the switch itself or the system connects the circuit to ground. When you move the switch to 'on' or use the other two lights, you are connecting the negative side of the bulb to ground (W-B). When you open a door, the ECU senses it (actually the door switch grounds itself) and then the ECU grounds the G-W wire.

I'm not seeing in the diagrams you posted where the wiring goes through another light. The G-W wire goes directly from the dome light to the driver's side fuse/junction box (connector 2A, pin 3), then to connector 2P, pin 60 (that's the one on the side with all the SB wires), and finally to the instrument ECU. You could put the dome light into door mode, unplug 2A (just to be safe), and short pin 3 in 2A to ground. The dome light should light up.

You mentioned the other two lights. According to the diagram, all three lights use the same hot (red) and ground (W-B) when turned to 'on' so they should all work if you have voltage and that ground is good. It likely won't matter for those bulbs if they are LED since there is a physical disconnect when they are off (ie they shouldn't glow). Also don't forget that LED bulbs typically have polarity. That means if they don't work one way, you flip them around.

Finally, you can put your multimeter in continuity mode and check from the green wire in the dome light to 2A pin3, then 2P pin 60 and then at the junction ECU Connector A pin 2. If you have continuity the whole way, then the ECU probably went down.

Oh, one other thought. Does your door ajar light up when the driver's door is open? What about the passenger door? If not, then you might have ECU troubles.

My instrument cluster door ajar light works and so do the door courtesy lights.

I’m having issues with the key ring light as well. Not the same circuit but grounds to the ecu.

I’m going to pin test the g/w wires and see what comes up.

Best case it’s the wire but it’s probably the junction box or ecu at this point if it’s the 2 circuits?

I’m not sure how the key ring would have anything to do with it but it is tied in to the courtesy lights so it kinda makes sense. I did put a 74 sylvaina bulb in that socket it lit up but wouldn’t seat properly now I can’t get light from that socket, it has voltage but the ground going to the ecu might have been what caused my dome light issue?

You’re right I should just live with it, although I’d like to figure out what happened and if anything else got affected?

 

[asmara]

I have to admit, I'm a little unclear now. Besides the dim glow (which I think would actually mean that the wire is going back to the ECU since the circuit has to complete somehow), what is actually broken?

 

[Green2000LX]

I have to admit, I'm a little unclear now. Besides the dim glow (which I think would actually mean that the wire is going back to the ECU since the circuit has to complete somehow), what is actually broken?

Apologies for the confusion!
The light around the ignition isn’t working properly either (gets voltage won’t light up a bulb) since that light comes on when the dome light should come on I’m wondering if that somehow governs the dome light turning on with the doors?

I haven’t tested further down the green wire yet. I’ll try that tomorrow.
If I blew 2 fuses when I was putting the bulbs in wound the kick panel jbox be the problem?

The dome light works when the switch is set to on but not door. It was really dim when I first put leds in the rest of the sockets. It won’t light dim anymore.

Im sorry for overthinking this.

 

[asmara]

Apologies for the confusion!
The light around the ignition isn’t working properly either (gets voltage won’t light up a bulb) since that light comes on when the dome light should come on I’m wondering if that somehow governs the dome light turning on with the doors?

The dome light works when the switch is set to on but not door. It was really dim when I first put leds in the rest of the sockets. It won’t light dim anymore.

Got it. You are looking at what are essentially 3 different circuits.

I'm making the assumtion that you didn't unplug any connectors and just messed with the dome lights and replaced the two fuses.

Easy one first - Dome light works when you switch it to on. Make sense, the ground there is a hard wired ground and you have voltage.

The other two likely have the same issue. The Instrument Junction ECU should ground them when the door is open and it isn't. You know this isn't a fuse problem because this is a negative switched system and you have power both at the dome light and at the ignition bulb. That means that the Instrument ECU, which controls the door ajar light as well, is only partially working. When it was working, you were seeing the dome bulb glow because the electronic switching to ground done by the Instrument ECU was letting a tiny bit of current flow which caused the LED to illuminate. Assuming the led dome bulb is in the same orientation as when it glowed, then the ECU is no longer letting that tiny bit of current to flow. That tells me you may have fried the instrument ECU.

What I would check now - check continuity between the G-W wire at your ignition light and ground. When the door is closed it should be an open circuit. When the door is open, you should see a connection to ground. If you don't see this, it is likely the Instrument ECU. The power to the ignition light come from the same source that feeds the door ajar light on the dash so it confirms your check that there is voltage there.

All of this is in the "Multiplex Communications System" section of the wiring diagram.

 

[Green2000LX]

Got it. You are looking at what are essentially 3 different circuits.

I'm making the assumtion that you didn't unplug any connectors and just messed with the dome lights and replaced the two fuses.

Easy one first - Dome light works when you switch it to on. Make sense, the ground there is a hard wired ground and you have voltage.

The other two likely have the same issue. The Instrument Junction ECU should ground them when the door is open and it isn't. You know this isn't a fuse problem because this is a negative switched system and you have power both at the dome light and at the ignition bulb. That means that the Instrument ECU, which controls the door ajar light as well, is only partially working. When it was working, you were seeing the dome bulb glow because the electronic switching to ground done by the Instrument ECU was letting a tiny bit of current flow which caused the LED to illuminate. Assuming the led dome bulb is in the same orientation as when it glowed, then the ECU is no longer letting that tiny bit of current to flow. That tells me you may have fried the instrument ECU.

What I would check now - check continuity between the G-W wire at your ignition light and ground. When the door is closed it should be an open circuit. When the door is open, you should see a connection to ground. If you don't see this, it is likely the Instrument ECU. The power to the ignition light come from the same source that feeds the door ajar light on the dash so it confirms your check that there is voltage there.

All of this is in the "Multiplex Communications System" section of the wiring diagram.

I haven’t gotten around to testing the GW wire yet.

Looking around at the circuit in the manual, would a relay be what triggers those lights to come on? It seems like the dome light goes to the ds panel before the instrument ecu?
I noticed on the ds kick panel there’s a dome relay.

I definitely broke the ignition light before the dome light issue.

I also have had a non working speedometer for a few years. I definitely have a bad group a wiring in the dash somewhere, my driver door wiring need to be repaired as well. Only the lock and windows work on that door currently.

Can those shorted/ severed wires cause these problems? I’m aware it’s a separate circuit. It makes sense that one or two wires can cause a lot of problems.

 

[asmara]

I haven’t gotten around to testing the GW wire yet.

Looking around at the circuit in the manual, would a relay be what triggers those lights to come on? It seems like the dome light goes to the ds panel before the instrument ecu?
I noticed on the ds kick panel there’s a dome relay.

I definitely broke the ignition light before the dome light issue.

I also have had a non working speedometer for a few years. I definitely have a bad group a wiring in the dash somewhere, my driver door wiring need to be repaired as well. Only the lock and windows work on that door currently.

Can those shorted/ severed wires cause these problems? I’m aware it’s a separate circuit. It makes sense that one or two wires can cause a lot of problems.

The dome lights are controlled by the Instrument ECU. The Instrument ECU is what triggers the dome relay. There is power at the dome light because you can turn it on. You noted power at the key illuminations. In both instances, that power comes from the Dome relay (which the instrument ECU had turned on). The next step after power from the kick panel is routed to the dome light, which is then connected to the instrument ECU, where it is grounded when the ECU is triggered by the door switch, etc.

Shorts, backfeeds, or poor wire harness repairs are a troubleshooting nightmare. When I bought mine, I spent the first two months with wiring diagrams chasing down botched repairs and backfed circuits.

You won't know anything until you start tracing circuits. Start with the GW wire. I suspect that you will find it isn't going to ground when a door is open. Right now, everything points to a fried ECU. If you don't feel like tracing circuits, pull it and open it up, and just give it a physical inspection. Mine that was fried was visibly fried. The photo doesn't really make it as obvious as it was but at the very least, those two resistors were toast.

 

[Green2000LX]

The dome lights are controlled by the Instrument ECU. The Instrument ECU is what triggers the dome relay. There is power at the dome light because you can turn it on. You noted power at the key illuminations. In both instances, that power comes from the Dome relay (which the instrument ECU had turned on). The next step after power from the kick panel is routed to the dome light, which is then connected to the instrument ECU, where it is grounded when the ECU is triggered by the door switch, etc.

Shorts, backfeeds, or poor wire harness repairs are a troubleshooting nightmare. When I bought mine, I spent the first two months with wiring diagrams chasing down botched repairs and backfed circuits.

You won't know anything until you start tracing circuits. Start with the GW wire. I suspect that you will find it isn't going to ground when a door is open. Right now, everything points to a fried ECU. If you don't feel like tracing circuits, pull it and open it up, and just give it a physical inspection. Mine that was fried was visibly fried. The photo doesn't really make it as obvious as it was but at the very least, those two resistors were toast. View attachment 4135889

I unplugged connector 2A and had low resistance when tested. So the GW wire is good!! I didn’t want to pull a headliner.
I was going to try to short the GW when unplugged but that connector sends power to the dome lights.

I ordered a new instrument ecu.
I’m hoping that’s the fix for these issues.
I’m considering trying to replace the whole dash wiring harness to eliminate all the previous owner splices. (The Sky blue wiring seems too difficult to trace)

How should I test the key illumination? One lead on the power side and one on the ground? Then toggle door switch?

 

[asmara]

I unplugged connector 2A and had low resistance when tested. So the GW wire is good!! I didn’t want to pull a headliner.
I was going to try to short the GW when unplugged but that connector sends power to the dome lights.

How should I test the key illumination? One lead on the power side and one on the ground? Then toggle door switch?

What did you actually test with the GW wire? My suggestion was to test the wire to ground with the door open (which should show continuity) and then again with the door closed (which should show an open circuit). You can't unplug the connector to check that because we are seeing if the ECU makes the ground connection. It sounds like you checked the continuity of the wire between the ECU and the dome light. Good to know that it is fine. The check to ground when plugged in will tell you if the ECU is bad or not.

If you want to see if the lights illuminate and simulate the door being open, unplug connector A from the ECU and manually ground pin 1 to the chassis (you can just ground it to the big metal bracket in the dash, or I use the door latch or even the key in the ignition sometimes). The ignition light should go on. If it doesn't, make sure the hot wire to the bulb has voltage, but I think you already checked that. If you ground pin 2 and your dome light is in door mode, the domelight should come on.

 

[Green2000LX]

What did you actually test with the GW wire? My suggestion was to test the wire to ground with the door open (which should show continuity) and then again with the door closed (which should show an open circuit). You can't unplug the connector to check that because we are seeing if the ECU makes the ground connection. It sounds like you checked the continuity of the wire between the ECU and the dome light. Good to know that it is fine. The check to ground when plugged in will tell you if the ECU is bad or not.

If you want to see if the lights illuminate and simulate the door being open, unplug connector A from the ECU and manually ground pin 1 to the chassis (you can just ground it to the big metal bracket in the dash, or I use the door latch or even the key in the ignition sometimes). The ignition light should go on. If it doesn't, make sure the hot wire to the bulb has voltage, but I think you already checked that. If you ground pin 2 and your dome light is in door mode, the domelight should come on.

I was confused when you said to unplug 2A to short it out. I didn’t have any luck doing that (wasn’t sure how) I did check continuity between 2A and the dome light. I’m gonna test the side going to the ECU tonight.

I’m learning so much about electronics! It makes sense that a resistor or capacitor it the problem?

I’m definitely chasing around looking at where everything is routing to/from.

 

[asmara]

I was confused when you said to unplug 2A to short it out. I didn’t have any luck doing that (wasn’t sure how) I did check continuity between 2A and the dome light. I’m gonna test the side going to the ECU tonight.

I’m learning so much about electronics! It makes sense that a resistor or capacitor it the problem?

I’m definitely chasing around looking at where everything is routing to/from.

So if you have continuity between 2A and the dome light, you know that wire is good. That wire goes to the ECU where it is internally switched to ground. If you unplug connector A, your dome light switch is on 'door', and you run a wire from 2A to any grounding point on the LC, your dome light should come on.

You are just simulating what goes on in the ECU when it sees the door ajar trigger by completing the circuit.

 

[Green2000LX]

So if you have continuity between 2A and the dome light, you know that wire is good. That wire goes to the ECU where it is internally switched to ground. If you unplug connector A, your dome light switch is on 'door', and you run a wire from 2A to any grounding point on the LC, your dome light should come on.

You are just simulating what goes on in the ECU when it sees the door ajar trigger by completing the circuit.

Yes!!!! I got it fixed the ecu got cooked I put my eBay junction box in and all is good now!!


Thank you so much for helping narrow it down!

 

[asmara]

Great news. Glad it is all working.

If you have time, open the old one up and post a picture of the circuit board. I'd be curious to see if what got fried is visible (and if it was the same thing that killed mine).

 

[Green2000LX]

Great news. Glad it is all working.

If you have time, open the old one up and post a picture of the circuit board. I'd be curious to see if what got fried is visible (and if it was the same thing that killed mine).

Absolutely I don’t have my lx until Tomorrow. I’m getting a timing belt done and a few other things. I swapped in my eBay ecu and without me testing anymore!

I definitely somehow backfeeded voltage to it?

 

[asmara]

I definitely somehow backfeeded voltage to it?

No way to really know. It could have just died.

 

[Green2000LX]

No way to really know. It could have just died.

my truck has so many electrical problems its hard to tell. My mechanic scanned it today, lots of codes came up. cdl open circuit, master cylinder, abs, steering tilt.
These are amazing cars but they definitely have some electrical aging issues. I found this nice little surprise for the radio connector gotta love previous owners l!