Tailgate Couresty Switch - What Wire?

[96TrailSurfer]

I've set up extra lights in the tailgate and wanted to have them come when the tailgate opens. Stock rear dome light is ground switched - with the switch in the tailgate latch. When the tailgate is closed, dome lights have a ground.

Inside the tailgate is a 20 pin connector to the tailgate ECU, and 3 smaller connectors. I found one of the small connectors that goes to the latch switch - when I unplug this connector, the dome light goes off. The other connectors have no effect on the dome light.

My problem is that I cannot find the pin(s) on that connector that actually change state when the latch is opened or closed. About half of pins are always grounded, and don't change.

So, any idea of which wire(s) I need to be tapping into? Wiring diagrams that I have provide no help - I found the wire referred to (Blue-White), but it doesn't seem to change state.
Image may contain: tree and outdoor

 

[4Runner4Leon]

Is this for your '96? The wiring diagram you posted is for a '02, which is totally different.

The wiring diagram I have for a '98 shows a R-W wire as being grounded when the switch is closed.

 

[96TrailSurfer]

Is this for your '96? The wiring diagram you posted is for a '02, which is totally different.

The wiring diagram I have for a '98 shows a R-W wire as being grounded when the switch is closed.

You are correct, 02 tailgate wiring is different, but I couldn't find a wiring diagram for a 96 unfortunately.

I'll try to find the R-W wire - that said, there was no wire on that connector that changed state when the switch was closed

 

[4Runner4Leon]

You are correct, 02 tailgate wiring is different, but I couldn't find a wiring diagram for a 96 unfortunately.

I'll try to find the R-W wire - that said, there was no wire on that connector that changed state when the switch was closed

See the attached diagram for '98. The R-W wire that the courtesy switch grounds is at the B-9 connector, it's a 2-pin connector. I don't think there's a rear door ECU on these earlier models.

 

[96TrailSurfer]

See the attached diagram for '98. The R-W wire that the courtesy switch grounds is at the B-9 connector, it's a 2-pin connector. I don't think there's a rear door ECU on these earlier models.

There is a backdoor ECU (at least there is one on my 96 Surf and I think it's identical to a 4R of that year), but it is different from the 00+ ECU.

 

[4Runner4Leon]

There is a backdoor ECU (at least there is one on my 96 Surf and I think it's identical to a 4R of that year), but it is different from the 00+ ECU.

Find the wire that gets grounded by the switch (like the R-W wire shown above), then tie the ground of your new lights to that wire. It'll get shorted when the switch is activated, illuminating the lights.

 

[96TrailSurfer]

I must be missing something painfully obvious

The diagram says that the door switch connects R-W from the courtesy light to W-B ground.

The grey 10 pin connector has both RW and WB

The grey connector definitely controls the dome lights.

I took apart the switch and saw that it goes to a 2-pin connector with RW and BW wires.

BUT!!!!

Both RW and WB pins on the grey connector are always grounded, whether or not the door switch is open or closed. Tripping the door switch makes no difference.


What am I missing?

 

[4Runner4Leon]

I must be missing something painfully obvious

The diagram says that the door switch connects R-W from the courtesy light to W-B ground.

The grey 10 pin connector has both RW and WB

The grey connector definitely controls the dome lights.

I took apart the switch and saw that it goes to a 2-pin connector with RW and BW wires.

BUT!!!!

Both RW and WB pins on the grey connector are always grounded, whether or not the door switch is open or closed. Tripping the door switch makes no difference.


What am I missing?

Is your rear courtesy light (tailgate area) working correctly?

 

[96TrailSurfer]

Yep, works perfectly

 

[4Runner4Leon]

Yep, works perfectly

OK, and when you say that the R-W terminal is always grounded, is that with the tailgate open and closed? According to the wiring diagram, R-W only gets grounded with the tailgate open. Did you actually check R-W to ground resistance with the tailgate closed?

 

[96TrailSurfer]

OK, and when you say that the R-W terminal is always grounded, is that with the tailgate open and closed? According to the wiring diagram, R-W only gets grounded with the tailgate open. Did you actually check R-W to ground resistance with the tailgate closed?

Exactly.

I am using a continuity tester (i.e. diode setting on my multimeter) to check for continuity from gnd (chassis) to the R-W terminal, and from R-W to W-B terminals. I am testing the male side of the connector, i.e. the one in the back of the picture, that runs inside the tailgate to the latch switch and other places, rather than the female part is part of the loom that ultimately runs though the tailgate grommet.

Based on this, R-W is always grounded, and there is always continuity between R-W and B-W whether or not the tailgate latch is closed.

I didn't check actual resistance from R-W to GND, but as I recall, continuity tester beeps if resistance is less than 5 ohm, i.e. nominal.

It's a PITA to test with tailgate closed, but you get exactly the same result by simply manually moving the latch in the lock to closed position, and the resetting to open by pulling the tailgate handle (I tested and confirmed this with the dome light).

I guess my text step is to disassemble the entire gate and try to tap into the 2 wires that run directly from the latch switch to the 2-pin connector inside, but that involves more disassembly that I probably don't want to do.

 

[4Runner4Leon]

OK, so I see a problem. We've been looking at the wrong switch ("back door courtesy switch"), which of course is for the rear side doors, not the tailgate! We should have been looking at the "Interior Light (Rear)" portion of the wiring diagram, the one with R and L-Y wires coming to it. Unfortunately it is not clear to me what grounds that R wire to have the light come one. I'll have to sturdy the diagram some more.

 

[96TrailSurfer]

OK, so I see a problem. We've been looking at the wrong switch ("back door courtesy switch"), which of course is for the rear side doors, not the tailgate! We should have been looking at the "Interior Light (Rear)" portion of the wiring diagram, the one with R and L-Y wires coming to it. Unfortunately it is not clear to me what grounds that R wire to have the light come one. I'll have to sturdy the diagram some more.

alas, no. "Back door" in Toyota parlance is the tailgate, while the rear side doors are "rear doors".

You can also see it on the diagram, the rear door courtesy switches are on the bottom of the diagram, beside the front door courtesy switches, and they are used to control the Interior Light (Front) rather than the Interior Light (Rear).

The L-Y wire provides power, it's a common power rail for all lights, through the AM2 fuse and the integration relay. It's not switched. Toyota (quite smartly, to minimize wire runs and risk of shorts) uses ground switching wherever possible.

 

[4Runner4Leon]

alas, no. "Back door" in Toyota parlance is the tailgate, while the rear side doors are "rear doors".

You can also see it on the diagram, the rear door courtesy switches are on the bottom of the diagram, beside the front door courtesy switches, and they are used to control the Interior Light (Front) rather than the Interior Light (Rear).

The L-Y wire provides power, it's a common power rail for all lights, through the AM2 fuse and the integration relay. It's not switched. Toyota (quite smartly, to minimize wire runs and risk of shorts) uses ground switching wherever possible.

Right you are, so back to the original thought process. That R-W wire should be getting grounded only when the tailgate is open. I'm not sure that you are testing at the B9 connector, I'd test it there.

 

[96TrailSurfer]

Exactly ... should be ...

I am pretty sure I am testing it at B9, how can I confirm which connector is B9?

 

[4Runner4Leon]

Exactly ... should be ...

I am pretty sure I am testing it at B9, how can I confirm which connector is B9?

B9 is the two pin connector shown below:

 

[96TrailSurfer]

B9 is the two pin connector shown below:

Hmmm... that looks like a wiring diagram for a vehicle without a backdoor ECU. Different from mine.