Wacky Instrument Cluster Issue

[phattyduck]

Edit: Was reviewing past comments and you were having trouble reading speed using Torque Lite? OK that's weird. Leaning more toward the abs/speed sensor speedometer side.

Not too weird. The ABS system sends a speedo signal to the gauge cluster, which then modifies it and sends it to the ECU. If the speedo is whacko, it could/would affect the speedo signal to the ECU. It is a hold over from older Toyota setups that either had mechanical speedos (where the electrical drive to the ECU was in the gauge cluster) or electric speedo drivers (where there still was electrical modification of the speedo signal before it was sent to the ECU).

-Charlie

 

[cahilc]

Gotcha Charlie & TX.

Trying to see if we can break down the circuit into smaller diagnostic chunks.

Or if there's another way to disconnect something besides battery or dome fuse that would clear the cluster. Help narrow down the view of the problem.

Cheers - Cahil

 

[hamsandwiches]

Ok so in an effort to narrow the issue down - I have found that the problem resets just like pulling the dome fuse if I pull this blue plug from the back of the cluster - guess now cut each wire next time it happens?? I will look back at the diagrams and see if the color of the plugs is labeled.

Also - pulling ABS fuse does nothing and unplugging the fuel tank plug does nothing.

This is that plug that when pulled, resets it.

 

[phattyduck]

That blue connector is "C28" or D on the Combination Meter pages.

Pin Color Function
1 Gr-L Raw speed signal from ABS ECU
2 B Tachometer signal from igniter
3 G-O Conditioned speed signal out to ECU, etc
4 Y-R Fuel Level Sender
5 O Fuel Level Sender
6 Br-B Ground for Fuel Level Sender
7 B-W Neutral signal
8 Couldn't find this on the diagrams, probably unused?
9 Should be unused
10 G Illumination power (10A Tail fuse) and other unknown functions
11 W-G Illumination variable negative voltaget (to rheostat)
12 L-Y To 15A Dome fuse (door ajar light and other unknown functions)

So, next try pulling these fuses individually:
- 10A Tail
- 15A Dome

And see if either/both reset it.

-Charlie

 

[hamsandwiches]

duck, thanks so much for that info!

the 15 amp dome resets it - I am not sure about the 10 amp tail fuse

 

[phattyduck]

guess now cut each wire next time it happens??

Don't be cutting wires! You can remove wires individually from those plugs (just take note of where it goes back!) if you have a small pick and you lift up the pin retainer.

-Charlie

 

[hamsandwiches]

While its plugged in??

 

[phattyduck]

While its plugged in??

No, you won't be able to remove wires while it is plugged in, sadly...

Another thought I had - removing the Dome fuse resets it, but any of the wires on either the blue or white connector could be the thing that initiates the problem.

It is just so weird that two different gauge clusters had the same (ish) issue!

-Charlie

 

[hamsandwiches]

Right, but unplugging the blue plug resets it - so how would I go pin by pin with it plugged in without cutting/reconnecting each wire?


As soon as it resets, I have to wait for it to happen again which is extraordinarily inconvenient.

I think the fact that the same thing happens on a different cluster is enough reason to believe the issue is not the cluster(s)

 

[cahilc]

Has anyone made a 'breakout box' for that blue connector?

Would be possible to make a breakout box for the connector with long enough wires to bring the access box eternal to the dash.

Install, drive around until the condition happens the look at the box for lights and disconnect the individual lines accordingly.

Would eventual find the exact line but I'm not convinced of a solution yet because of a lot of unknowns of how the circuit works.

Not sure yet if it's a physical problem (voltage/resistance) or a logical problem (chips/logic) . Seems to be leaning toward the latter.

Edit: definitely 10a tail fuse check and would be worthwhile checking those lines against the combination meter diagnostic.

- Cahil

 

[hamsandwiches]

So the issue relentlessly persists - I found that cutting the last wire on that list from the blue plug is the one that resets it

12 L-Y to 15A Dome fuse resets it - this is not a big surprise as pulling the dome fuse resets it as well

I am close to giving up but I really love this 4runner and want to keep it

Any more instructions? Main ECU?

 

[photoleif]

i'm reading this cringeworthy thread and was so hoping it would end with something brilliant and final. i would be so frustrated.

i am back to something that cahilc was on to earlier, namely voltage. sorry if i've missed it, but have you checked the voltage to the cluster? mine (a '99 manual) has i believe five of those annoyingly short connectors (though it feels like 40 of them). there are at least a couple grounds per the 'body electrical' pages, and as i recall, if any one of the plugs is not fully inserted, the indicators it controls all go out. it starts to make me wonder if something's up with either the connectors being bridged (probably not), a loose or low-quality ground (worth checking, especially with that one moronic plug that just touches the membrane, rather than snapping into a proper socket), or a batt+ that isn't making a good connection.

just confirming (i believe) what was already covered: it looks like the dome fuse protects the speedo, but the gauge fuse protects the odo/trip. obviously your odometer is on crack, but how's your trip meter? have you tried turning your rheostat to full on?

sorry if you've already tried all that... just trying the monkeys-typing-shakespeare approach here. apologies if it's only frustrating.

 

[hamsandwiches]

The trip is unresponsive when the condition happens - have tried moving the rheostat all over the place

Which grounds are you referring to?

Batt pos. is tight for sure

 

[photoleif]

each connector has at least one ground. the "E" connector appears to have two. i was just thinking, it's at least possible that the leads may not be making good connection. but heck i just don't know. do you have the electrical diagrams handy?

 

[hamsandwiches]

I believe the gauge cluster wiring diagrams were posted on this thread a few pages ago.

I am going to pull a main ECU tomorrow from the yard. Will it matter if it is from a wrecked 4runner? It's another 2000 (no airbags went off) same one I got the body ECU from.

 

[photoleif]

i don't think an ECU from a wrecked 4R is a problem. typically given their location they are fairly well-protected from front and rear impact. that's where i got mine, for my 3slo conversion in my pickup, and that ECU still works great after six years (can't say as much for the engine, which self-destructed last fall). so long as the body matches your 4R's body and probably the transmission is a match, too, i don't see an issue. definitely see if anyone else has concerns.

 

[hamsandwiches]

Ok. I am going to spend a while at the yard today tearing apart this 2000 for all the electronics I can find.

Was greeted with this joyful occurrence only a few miles into driving yesterday.


Thanks for all the advice this far guys. I don't want to throw the towel in yet.

 

[hamsandwiches]

Just got back with the loot: main ECU, ABS ECU, and this little ABS thingy

Which should I install first? Any bets?

 

[cahilc]

(open Jeopardy game show mode)

Alex...
What is ABS/ECU? For the win.

(close Jeopardy game show mode)

And/or that ABS thingy would be second guess.

Hoping...

Cahil

 

[photoleif]

fwiw i'd definitely swap in the ECU first. that kind of mindless behavior by your instrument panel, behavior that defies ten kinds of troubleshooting, starts to make me think the ECU's got some damage. make sure that you do that with the battery disconnected, and i'd also be (probably needlessly) thorough and pull and re-insert the ECU relay.