TheDurk
Elite Member
Yes and yes.
Dome light problem
- Thread starter TOYO 4R SR5
- Start date
Yes and yes.
ajonesnv
New member
OK. So got my hands on a BCM for fairly cheap to see if it was the BCM. No change with the newer one.
Still the rear dome light only works on "on" and not on "door." Ive checked all the switches in the hatch and at the light, they are functional. The front dome works fine and all the locks function with the door buttons and the keys in either door. The Key FOB does not...these two items stopped functioning at the same time.
Any other suggestions as to what to look for??
TheDurk
Elite Member
Hmmm. You should check the condition of the wires in the harness between the body and the liftgate up by the hinges. Those wires flex every time the liftgate opens and insulation flakes off and wires break. This is a common cause of rear end electrical weirdness. (The receiver the fob--no caps, it's just a fob--connects to is located in the liftgate.) Also, check your MPX fuse.
If that doesn't do it, time to open the liftgate up.
Does your rear defroster work?
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ajonesnv
New member
I’ve had the lift gate open and checked all the components (latch switch ohms out right, the switch at the light ohms out right too), including swapping out the ecu back there. I’ve pulled the rubber boot back as well, but couldn’t visually see any damaged wires.
The window, wiper, power locks work to the hatch as well...haven’t checked the defroster.
IBallEngineer
New member
Not to bust your chops, well ok maybe a little, but I'm not fond of terms like "ohms out", because it really doesn't explain how or what you tested. But let's assume the switch is good, did you check to see that the switch is grounding the pin 7 at the back door ECU? It gets a little dicey after that because the two ecu's talk through a serial data link. The Body ECU then sends a ground signal to the Combination meter, which in turn grounds the lamp. My money is on the connection at the left kick panel area (1E2, 22 pin connector), term 9, the light green/red wire is the ground circuit from the lamp, to the combination meter. You could ground this wire yourself and test the lamp and wiring up to that point. If continuity is good on the down stream side of the connector, the next point to check is at the combination meter itself. There you could check that the same light green/red wire Connector C27 terminal 9 is good and you can ground it there to double check, then you will have to check what is happening at terminal 11 to see if the body ecu is grounding that side. Then the green/white wire at the body ECU, only I can't figure out what connector or pin. Maybe El DUrko can chime in here. [MENTION=10169]TheDurk[/MENTION] is famous, he was in that movie the Good the Bad and the Ugly, not sure which one was him.
:banana:
ajonesnv
New member
My head just exploded! So out of curiosity, if the switch is good at both the door and the lamp does. And assuming the wiring is not damaged. Is it safe to assume it’s probaby the ECU in the hatch or the BCM or even both? And then if so, how how specific are the model differences? I have a 99 SR5...the parts I sourced are from a 00 limited.
Pardon my ignorance !!!
TheDurk
Elite Member
Yeah, I was going slow on you. This one is actually a PIA to trace out, as old [MENTION=102597]IBallEngineer[/MENTION] over there points out. He's a good guy, but he gets excited and can dish out a very full plate.
You can't assume anything with electric. The fault is what the fault is.
As far as the parts, in general, '00 and '99 are electrical clones, but unless the p/n's match there are no guarantees.
My '99 EWD is a paper one, and I am looking for it. My suggestion is to test for a ground signal from the BCM at the Combo Meter, then see if the light operates when you provide that signal, and then go forward or back from there, depending on the results.
I just need to find that manual to tell you precisely how to do it.
IBallEngineer
New member
Ignorance is not a crime! Basically we can't assume anything. There are a few connector points that could be the problem, that is why I put money on the kick panel connection. Also the Combination meter acts as a sort of ground logic distribution point for the interior lighting. What El Durko is looking for is the connector and pin # that would allow you to test to see if the Body ECU is grounding the light. The first part of my response was for you to test that the door switch was telling the Rear Body ECU that it was grounded.
Not rocket science, but in this case, just a little peculiar.
:couch2:
IBallEngineer
New member
Heh, yeah I'm a good guy, just ask my wife, scratch that, ask my dog.
In fairness I can't hang out here and dole out instructions one line at a time anymore, so I threw the whole shibang out there. Too bad I found that wall at the Body ECU.
:lookout:
ajonesnv
New member
OK. So bear with me. There is a connector behind the base of the kick panel that I can get continuity through to the light. If I ground it from there the light will turn on. From there up, Im not quite sure where the wire goes...the wire follows a large grouping that seems to go up into the dash. Is this where the combination meter is??
Also, the truck always thinks the door is shut, meaning the dash light doesn't come on like the other doors when they are open. Also, about the same time this all happened or at the same time the key fob stopped working, does this help narrow down possibilities?
Also, the truck always thinks the door is shut, meaning the dash light doesn't come on like the other doors when they are open. Also, about the same time this all happened or at the same time the key fob stopped working, does this help narrow down possibilities?
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IBallEngineer
New member
Well yes and no! If you ground the wire and you turn on the light, it means the Body ECU and the Combination meter and rear body ECU are being bypassed. And yes the wires continue to the Combination meter, which is the instrument panel.
As for the Door open light, that requires that the body ECU tell the combination meter that the door is open. If El Durko can't tell us which pin to test at the Body ECU, you can test at the Comb Meter if you are so inclined. Connector C17, pin 11, Green/white wire. With the back door open, ground should be present on that wire. If there is, apply ground and see if the light turns on, if it doesn't, the problem is in the Comb Meter. If there is no ground present with the back door open, we can move to either the back door, or the Body ECU.
ajonesnv
New member
So I have traced wires form the parts of the truck I already had open based off of your guy's help. Im thinking I will need to pull the Combination Meter and check for the fault there. (I had the lower dash and the rear hatch all ready taken apart, so I figured it easiest to start there.)
Its my understanding that the CM's aren't simply interchangeable due to the milage...is this right? I know Im jumping ahead, as I haven't checked it yet, but curious all the same.
I attached a PDF of the interior light schematic and marked what I have done...any other suggestions other than what you have given me??
EDIT! I cannot attach the PDF. Dont know why.
Link to view:
https://www.dropbox.com/s/vx4ob5np9uu1l47/Interior.pdf?dl=0
Its my understanding that the CM's aren't simply interchangeable due to the milage...is this right? I know Im jumping ahead, as I haven't checked it yet, but curious all the same.
I attached a PDF of the interior light schematic and marked what I have done...any other suggestions other than what you have given me??
EDIT! I cannot attach the PDF. Dont know why.
Link to view:
https://www.dropbox.com/s/vx4ob5np9uu1l47/Interior.pdf?dl=0
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IBallEngineer
New member
Well I don't have personal experience changing one on a Toyota, I did one on a Ford and the mileage was stored in the ECU and the mileage self corrected. Or was that a Chrysler, I'm not sure! Haha. Anyway, I bet you could find a way to bypass it, but then your door open light would never work. If only El DUrko would figure out how to test the Body ECU! [MENTION=10169]TheDurk[/MENTION]
ajonesnv
New member
I actually already ran the wire while I had it open. Just gonna do the CM testing before I commit one way or another.
I replaced the BCM already, my only concern is that it was from a 2000 limited, so its questionable as to its compatibility.
IBallEngineer
New member
Well if you replaced the Body ECU, and everything else works, that isn't going to be something very different. The differences are more in the theft deterrent and such systems. You can jumper the wires on the 20 pin connector on the back of the Combination Meter. Pin 11(grn/wht) and Pin 12(Blue/Grn), that takes only the CM out of the loop. You can just ground Pin 11 but that leaves the kick panel to CM wiring on the pin 12 circuit unconfirmed.
I know I take too big a bite!
