Help an idiot figure out why my truck thinks my doors are open (dim cluster light)

[MongooseGA]

I'm half an idiot, and a full one when it comes to electrical. Must be my specific brand of the 'tism or that gifted child syndrome, but I simply cannot wrap my head around electrical.

That said, I've been trying my damn-dest to figure out why my truck has been displaying a dim 'door open' light on the cluster for a while. I feel I've gotten to the end of what I can try diagnosing myself, and need to open up to the brain trust. Other threads on this topic didn't seem to lead anywhere that matches my issue.

The truck: It's Gerry. Some of y'all know her. 2005 LX470, 360k, lives in the driveway. Was my daily until I bought a 570 late last year. Very modified. Been everywhere and done everything. This issue began in the last year or so. Hard to say exactly because the truck has been sitting for about 9 months.

The symptoms: Cluster light for 'door open' is always illuminated, albeit very dimly when the doors are actually closed.
Result: My batteries keep going dead. Even with a solar charger hooked directly to the battery, the draw is overall greater than what the charger puts in.

What I've found: With a fully closed-up truck in 'sleep mode' (post shut-down), there is a parasitic drain of 180 milliamps (Reading 0.18 on my multi-meter). I began pulling engine bay fuses yesterday. Eventually I got to the front passenger kick panel and found that the 10A DOME and 10A ECU-B2 were my culprits. Removing the ECU-B2 fuse dropped the parasitic draw to .04/05 and dim cluster light goes out. If I pull the 10A DOME fuse first, draw drops to .10. Pulling ECU-B2 after brings it down to the .04/05. To me, this indicates that the ECU-B2 is being triggered by the DOME fuse. Something on the DOME circuit is staying awake and keeping the ECU-B2 awake as well. (Correct me if I'm misguided here). If I put both fuses back with no door sensors triggered, draw stays around .05 and the light stays off.

What I've tested: Yesterday I individually tested (and completely disconnected) all 4 door plunger sensors (all working correctly), all courtesy lights (also good), disconnected all 3 rows of overhead lighting (no change), disconnected the visors (no change) and disconnected the rear hatch latch wiring (no change). I also completely disconnected the cluster from the dash, which also yielded no change in parasitic draw. At the moment, all 4 door plungers are still disconnected, all overhead lighting is disconnected, both visors are disconnected, hatch latch is disconnected. I have re-connected the cluster. I disconnected all 4 harness plugs on each DS/PS kick panel that come out of the door panels. On each side, 2 go to other harnesses and 2 go to their respective fuse boxes. No change in draw from any of this. All are now reconnected. For what it's worth, all overhead lighting, door lighting, etc, work properly. There is no noticeable problem other than this cluster light.

With all of this, I still have the issue. If I install a door sensor and trigger it, the truck will correctly recognize a door being open and turn on the bright cluster light. Draw jumps to .48(ish). If I then close the door or remove the plunger, the cluster light stays on dimly and draw settles back to .18. So I know the issue is triggered when the truck recognizes a door open, and will only clear if I pull those fuses to reset. Ok, maybe this is a mechanical issue, like a short somewhere. Today I pulled all of the door sills and B pillar trim to inspect the wiring harnesses. Nothing was obviously damaged, although I have submerged this thing in mud before, years ago. At that time, I pulled out the interior and thoroughly cleaned the channels under the carpet. Today, I jiggled the crap out of the harnesses on both sides to watch for any change on my meter, no changes. The harnesses, at least in the sills, seem to be fine.

So here's where I'm at a loss. Gerry is kind of famous for fixing little issues on her own, but this one is sticking. I did check my sunroof drains today. DS was good, PS had a little blockage. I ran trimmer line down each then blew them out with shop air. There was a small puddle under the PS after doing this. I have not added any electrical accessories to the truck in the time this has been going on, although I did remove my whale-tail spoiler and install an OEM 3rd brake light. Old spoiler holes are sealed with waterproof tape, I'm pretty confident there isn't any leaking happening in the hatch. I can still lock/unlock my doors remotely (saw this mentioned in another thread).

So... thoughts? TIA. Anyone who is able to help me figure this out gets a coupon to theartisangarage.com and a T-shirt!

 

[SMLE]

Just to confirm my understanding, have you checked the triggering of the dash light/remaining dimly is the same by reconnecting and then disconnecting each of the possible sensors one by one?

Considering you've suggested you're bad with electrics, you've done a good job with ruling out a lot of issues here!

I'm not super hot on electrics but you've done exactly as I would have done in terms of things to check.

Based on the fact you've established that regardless of the trigger point e.g. any door, the cluster light will remain on dimly, I would suspect there is a short somewhere in some wiring or bad connection in a plug or something.

I would now be looking at wiring diagrams for those two suspect fuses and seeing where they run from/to and checking those wiring runs with your multimeter.

I am not gifted in this department but I'd be establishing how the door sensors are wired e.g. if they are wired in some sort of series with all other door sensors where if one switch triggers then the circuit is connected/interrupted.

Interested to see how this is resolved, good luck!

 

[MongooseGA]

Thank you!

I went to each sensor individually. I can verify they each work by seeing the cluster recognize a door open when one is activated but the others would have been isolated (disconnected). Once all doors (including hatch wiring) were removed, the cluster light still persists and the draw remains are 0.18.

Unfortunately, I cannot read diagrams. That's kind of my crux in this. Friends have tried to help, I simply don't absorb it. I have done some digging and think there's a chance that the dome light fuse in the PS kick panel feeds power to a body control module in the driver's kick panel. I need to get my head back under the dash an eyeball it. For the time being, I may or may not have left my meter in the rain last night, which may or may not have toasted it, giving me bogus readings this morning. I may or may not have a new one coming first thing tomorrow AM.

 

[Super77]

Another half-idiot here. Does that make us a full idiot?

I dug into the 1999 FSM wiring diagram for this (heads up, mine's the 99 not a 2005 one, but the core design is almost certainly the same across those years).

My read of the EWD is that your dome/courtesy lights and the dash warning light aren't wired straight through the door switches like a simple light switch. They're wired to the Instrument ECU. The door switches just tell the ECU "this door is open or closed." The ECU then decides, on its own, whether to light up the dash warning AND the physical dome bulbs. Think of the ECU as the middleman relay, not a passthrough wire.

That explains why unplugging every bulb, every switch, and even the cluster didn't touch your draw. None of that reaches the part of the circuit that's actually staying on. If the ECU itself is hung up (reading a phantom "door open" signal, or just stuck from a fault), the draw lives inside the ECU's own circuit, upstream of everything you already tested. That also means pulling the fuse you pulled probably isn't "resetting" anything, it's just cutting power to the ECU and cluster entirely, which is why the light goes dark and the draw drops.

Given the light comes on dim rather than full bright, my best guess is something's feeding a weak, partial ground signal into one of the ECU's door-sense input pins, not a hard short and not a bad switch (you already proved that). That kind of soft signal is classic for moisture bridging a wire or connector. Worth remembering you pulled a puddle out of the PS sunroof drain right around when this started.

Next step I'd actually try: with everything still unplugged the way you have it, put an ohmmeter on each door-sense wire, right at the connector near the Instrument ECU, not at the door, and check for resistance to ground one at a time. You're not looking for a dead short, just any resistance at all. Whichever one shows something tells you which door's wire run to chase down instead of guessing with more fuse pulls.

If all four come back clean, next move is checking the ground straps and connections around the pillar trim you already had open, since a bad ground there can fake this same symptom without any wire actually being damaged.

 

[MongooseGA]

Another half-idiot here. Does that make us a full idiot?

I dug into the 1999 FSM wiring diagram for this (heads up, mine's the 99 not a 2005 one, but the core design is almost certainly the same across those years).

Here's the piece that actually explains a lot: your dome/courtesy lights and the dash warning light aren't wired straight through the door switches like a simple light switch. They're wired to the Instrument ECU. The door switches just tell the ECU "this door is open or closed." The ECU then decides, on its own, whether to light up the dash warning AND the physical dome bulbs. Think of the ECU as the middleman relay, not a passthrough wire.

That explains why unplugging every bulb, every switch, and even the cluster didn't touch your draw. None of that reaches the part of the circuit that's actually staying on. If the ECU itself is hung up (reading a phantom "door open" signal, or just stuck from a fault), the draw lives inside the ECU's own circuit, upstream of everything you already tested. That also means pulling ECU-B2 probably isn't "resetting" anything, it's just cutting power to the ECU and cluster entirely, which is why the light goes dark and the draw drops.

Given the light comes on dim rather than full bright, my best guess is something's feeding a weak, partial ground signal into one of the ECU's door-sense input pins, not a hard short and not a bad switch (you already proved that). That kind of soft signal is classic for moisture bridging a wire or connector. Worth remembering you pulled a puddle out of the PS sunroof drain right around when this started.

Next step I'd actually try: with everything still unplugged the way you have it, put an ohmmeter on each door-sense wire, right at the connector near the Instrument ECU, not at the door, and check for resistance to ground one at a time. You're not looking for a dead short, just any resistance at all. Whichever one shows something tells you which door's wire run to chase down instead of guessing with more fuse pulls.

If all four come back clean, next move is checking the ground straps and connections around the pillar trim you already had open, since a bad ground there can fake this same symptom without any wire actually being damaged.

Thank you! I will do these tests tomorrow when the new meter arrives.

 

[MongooseGA]

@Super77 , do you happen to see where those pins to test are located? I found reference to the 2D block behind the PS kick panel fusebox. I found pins B9 ( green w/ black) and B10 (red w/ yellow) are what I'm looking for on this side of the truck. If this is accurate (or if I can find otherwise) my plan tomorrow is to free the fuse block from its home and access the back side to test these pins. I imagine there's another on the DS as well.

 

[Super77]

Found the actual factory diagram for a 2005 LX470, not my 99 that I was cross-referencing before. But, I don't own a 2005 and haven't laid hands on this harness, so everything below is me (and my little FSM-trained AI friend) interpreting the diagram plus general electrical knowledge, not firsthand experience with your truck. Worth keeping in mind as you go.

On your B9/B10 question: There's no "2D" connector anywhere in this diagram. The kick panel connectors that do exist are named differently on each side (things like 2E, 2I, 2Q on the driver's side, 3D, 3I, 3Q on the passenger side). "B9" and "B10" do show up in this document, but as two unrelated things: B9 is part of the Body ECU's own connector housing, and separately it's a splice point in the passenger floor harness, not a numbered pin block you'd backprobe. Neither of those matches what you're describing, and the wire colors don't line up either. My best guess is you're looking at a different kind of reference (a connector location diagram rather than a circuit diagram), which would use totally different labels. Not saying you're wrong, just that I can't back it up with what I've got.

Here's what I can actually offer instead, straight off this diagram: each door switch wire has its own color, wired straight to the Body ECU.

• Driver door: R-Y wire
• Passenger door: R-B wire
• Rear driver side door: R-L wire (in Toyot-ese, 'L' usually means blue and 'B' means black)
• Rear passenger side door: R-G wire
• Back door (hatch): R-L wire (oddly, same color as rear driver door switch, so don't mix those two up if you're probing both)

Same setup as I described before: none of these switches wire directly to a bulb. Each one just tells the Body ECU "this door is open," and the ECU decides on its own what to light up, including your dash warning light. So, assuming this diagram is correct, chasing color, not connector number, is your best bet.

Suggested next move: instead of hunting for that 2D block, find the connector where those five wire colors above land (probably at or near the Body ECU itself, or wherever the harnesses converge behind the kick panel) and backprobe by color instead of by pin number. Same test as before, everything still unplugged the way you have it, check each wire for any resistance to ground, not just a dead short. Whichever color shows unusual resistance is your door to chase.

This view, from the same database, may also help you visualize the wiring.

 

[Super77]

Occurs to me that there is a second, related way to test: if you can reach the ECU that the door sensors feed into, and de-pin the individual wires until you see the dash light go out, that should immediately correlate a wire run (between the ECU and the door) to the problem. OTOH, if you do this and the problem does not go away, you may have an issue within or upstream of the ECU, in which case I'm tapping out

 

[ThomasGS4]

Another idiot here - and very off topic, but good to see you over here, Mongoose! I remember your Teal Mist SC400 from back in the day!

 

[MongooseGA]

Occurs to me that there is a second, related way to test: if you can reach the ECU that the door sensors feed into, and de-pin the individual wires until you see the dash light go out, that should immediately correlate a wire run (between the ECU and the door) to the problem. OTOH, if you do this and the problem does not go away, you may have an issue within or upstream of the ECU, in which case I'm tapping out

Fantastic, thank you. I likely was wrong, and that's what I get for wildly googling. I'll be on it in the AM.

Another idiot here - and very off topic, but good to see you over here, Mongoose! I remember your Teal Mist SC400 from back in the day!

Wow talk about a throwback! From CL, yeah? That SC was my first car in high school, and I'd love to have it again. Today I have a '97 6-speed with 65k on it. Beautiful car, and the reason my garage is too full to do all of this work inside

 

[MongooseGA]

My new multimeter arrived today, so I’m back at the truck with reliable gear. I need some help with physical identification so I don't guess at the wrong pins. Here is exactly where the truck sits right now:

All 4 physical door plungers, courtesy door lights, and overhead lighting/visors are completely disconnected. I have completely unplugged every single wiring harness from the front face of the driver's side interior fuse box (Junction Block No. 1) to isolate the wires from the computer.

The Big Clue: With the battery hooked up and every single front harness hanging loose in the footwell, the cluster door indicator light is still glowing dim. Based on @Super77 's diagram info, the door inputs are supposed to hit Connectors 1K and 1J at the Body ECU. I am trying to run an Ohm test to ground on the harness-side of those lines to see if my passenger sunroof leak physically shorted the cross-dash wire loom before it hits the computer. The problem is, I am colorblind (colorstupid, if you ask my friends), and looking at a dozen loose plugs with hundreds of wires is a needle in a haystack.

My questions for the 2003-2007 experts: Since the front face is fully unplugged, are 1K and 1J sitting right here in my hands on the front-facing harnesses, are they hidden on the backside of the box, or is the body ECU a module separate of the fuse box? Can anyone provide a photo, pin count, or physical description of what the 1K and 1J plug housings actually look like so I can count the raw pin slots instead of trying to look for the red/black or red/green stripe wire colors? Once I can identify the physical plugs, I'll pull the Ohm readings and update the thread.

Pics with the fusebox connectors still plugged in. I see a module directly above the fuse box.

I'm also wishfully hoping that Gerry will just fix this herself now that the sunroof drains have been cleared.

 

[Super77]

Something just occurred to me: if the Body ECU is the “traffic cop” for signals coming from the doors and going to the IP and the dome light, how does that lead to a dim warning light in the IP?

If you have a soft short between the ECU and the door, the ECU will read a semi-closed circuit, but why would it pass that on that to the IP in the form of a weak warning light? Seems like ECU logic would either fully turn on the warning light, or not.

So the issue may actually be between the ECU and the IP, but probably best to at least rule out anything between the doors and the ECU.