Wacky Instrument Cluster Issue

[hamsandwiches]

Ok so from what ive gathered, I will pull a body ECU, abs ecu, and all 4 wheel sensors if i can find them.

About to look through that diagnostic.

Thanks guys!

 

[hamsandwiches]

Durk, That instrument cluster test diagnostic is very thorough, but I'm almost positive the issue isnt the cluster because I already replaced that and it is giving the EXACT same issue now as the original cluster.

I see the truck body tests, I will look into those and also the wheel sensor tests

 

[phattyduck]

I don't think the ABS ECU or the wheel speed sensors are the problem - those wouldn't have anything to do with the tach or fuel level gauge... That's also why I asked if the OBD speed reading was still valid when the gauge cluster 'locks up' - it would tell you if that part of the circuit / truck is still working and it is just the display on the cluster that is going wrong.

-Charlie

 

[hamsandwiches]

Duck, I understand the tach and fuel gauge are on the same circuit as the speedometer, so maybe the weird signal from the ABS ECU is disrupting the adjacent gauges?

My OBD speed live data has never worked on torque lite, it cuts in and out from the correct number to zero. I only have tested that once this issue began.

Can't imagine that if thats the true data the engine ECU is receiving it wouldn't trigger a CEL or ABS light.

So basically I have no clue what the OBD speed reading is when the issue is happening or when its not.

 

[TheDurk]

Durk, That instrument cluster test diagnostic is very thorough, but I'm almost positive the issue isnt the cluster because I already replaced that and it is giving the EXACT same issue now as the original cluster.

I see the truck body tests, I will look into those and also the wheel sensor tests

Yeah, I was not suggesting the cluster tests. Just the body tests.

 

[phattyduck]

Can't imagine that if thats the true data the engine ECU is receiving it wouldn't trigger a CEL or ABS light.

The ABS computer triggers the ABS light (make sure it comes on for a few seconds when the truck is started).

A CEL for missing speed signal doesn't trigger right away, so that isn't much of a clue either way.

-Charlie

 

[hamsandwiches]

Any other suggestions? Going to the yard tomorrow hopefully will return with

Body ECU
ABS ECU
Wheel sensors


Will do body diagnostics when I'm back in the US

THANKS

 

[phattyduck]

Check part numbers (Body/ABS ECUs) and make sure they match what's in your truck currently.

-Charlie

 

[hamsandwiches]

Back in the US, going to yard tomorrow in search of body ECM, etc

Not sure if I am crazy, but it seems to happen way less when its like 100 plus degrees outside.

After I crossed Connecticut and the outside temp was going up past 100, it did not do it for the next 350 miles.

Any thoughts given that info?

Thanks

 

[rideexileex]

Back in the US, going to yard tomorrow in search of body ECM, etc

Not sure if I am crazy, but it seems to happen way less when its like 100 plus degrees outside.

After I crossed Connecticut and the outside temp was going up past 100, it did not do it for the next 350 miles.

Any thoughts given that info?

Thanks

From my own experience, faulty wheel sensors will trigger an ABS light, so I think you can rule those out.

 

[hamsandwiches]

Found this at the yard for $20 yippee

Will swap out the other 2 relays on the back of it first and if that doesn't work i Will install it

 

[hamsandwiches]

Ok folks, so I installed the "new" becm and the symptoms changed only slightly - instead of broken digits in the odo, when it happens I get this


I guess that means the BECM is connected to the cluster after all - but the issue persists.

I am at a loss at this point. main ECM?

 

[hamsandwiches]

Help? :cowboy:

 

[Piney]

I got nothing - except the old toyota 4wd vans (before Previa) used to have instrument clusters go weird and 'christmas tree' when the alternator began packing it in and mid-80s 911s lost their clusters when main voltage tanked.
And that's all I know about clusters.
So...
Grounding? At the cluster? Elsewhere (usual suspects).
Saw an alternator cable that broke inside the rubber casing and would sometimes move and briefly disconnect. That caused weirdness on the dash. Seen bad grounds be intermittent and do ghostlike things.
But I'm just sharing desperate thinking now.......

 

[cahilc]

I'll take a WAG at this.

So if I'm viewing that picture correctly...

In park.
Speedo registers 25 mph.
ODO weird characters.

Known good cluster. Swapped, problem remains.

Worthwhile to draw out the circuit for the speedo guage, odo, respective fuses, and battery connections. Everything that's in that circuit.

Yeah, break out that circuit with a hand written diagram. Old school.

The new diagram contains the problem. Minus super weird stuff, circuit interference, frequency overlap... Bleh. Uncommon for Toyotas.

Taking a snap shot 'right now' and your prior comment of 'happens less' in heat...

I'd be sure you speed sensor is withing spec.

And I'm not talking just voltage. If the speed sensor is sending back frequency static (rare but possible) can cause the ECM on the other end to go 'whacko'.

Like Durk mentioned before looks like an input problem.

Let's go after the inputs.

Possible next time this happens as in the picture above to unplug the speed sensor.

Any change in the cluster?

Same basic principle you did before with the battery cable but this time do it with the speed sensor.

Be safe under the truck, hot exhaust, safe place, etc.

And just for 'giggles' seriously, the maf was cleaned just before all this non sense started. I have zero faith it's the maf but humor me.

Unplug the maf? Any change in the cluster?

Let us know.

P. S. On your ODO change question, yes there are aftermarket (going into blackmarket) plugin tools for changing ODO readings. Google 'Toyota odometer correction tool'. Also possible to edit the hex table (in duplicate) and re-write new ODO miles. Third option, dealership maybe.

 

[hamsandwiches]

Thanks for the input Piney, I will look over grounds once again - but am led to believe it is related somehow to the becm because the symptoms changed slightly when I changed the becm unit - now when it happens the odo reads _ _ _ _ _ _ instead of broken digits as it did before - am I correct in assuming this means the becm is connected to the error?

 

[hamsandwiches]

cahilc, did not see your reply immediately. I will try the speed sensor unplug - however the speedo is no the only affected gauge - the tach and gas gauge are affected

as for inputs, that means there could be 3? the fuel level sending unit, engine speed sensor, and speed sensor

Not sure where the engine speed one is, but I know where the speedo and fuel sensor plugs are so I will try that next time it happens

Thanks!

 

[Piney]

I’d be drinking heavily by now thinking bad sensor, bad connection (jittery wire contact), wire broken inside sheath etc.
Momentary signal loss or gigo would not be unreasonable here.
You’re a better man than I am, Gunga Din ....

 

[phattyduck]

Not sure where the engine speed one is, but I know where the speedo and fuel sensor plugs are so I will try that next time it happens

Thanks!

Engine speed comes from the engine ECU, speedo signal comes from the ABS computer (if ABS equipped, almost all are), fuel level comes from the fuel level sender.

The '99+ gauge clusters do have a lot of 'smarts' in them, so many odd things could be happening if there is a fault.

-Charlie

 

[cahilc]

Think the original premise when this happens of being able to turn the truck off, disconnect the battery, and have the guages reset and work correctly is interesting. Also less problematic in a hotter climate.

Pretty much trying to use the same methodology but divide and concour.

The ecm/ecu/pcm/becm/abs/+ ... All those computer boxes (system) are going to fail or going to work properly(usually). The fact they work properly after a battery disconnect leads me to believe they're 'good'.

The change out of the becm affecting the guage is interesting but a side note. It changes the problem slightly but problem still persists. Digital displays are very voltage sensitive.

Since it's setup up as one big 'ganged' circuit (5v & 12v reference) plus those voltage lines feed everything.

We're looking for an input sensor to the computer system which has constant voltage reference with key off.

If the ABS is used for guage speedometer readings go after that sensor. Especially if there's constant voltage present.

Somethings telling the speedometer to go to 25mph and the fact of a scrambled odometer tells me bad or corrupt signal. The fuel guage acting weird could be overlap of the corrupt input signal at whichever computer box controls the fuel guage.

So basically pick an input sensor and disconnect. Simplified version of a battery disconnect.

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.