[APhelps]

Well I took my T4R to Moab and etc. this week / weekend and the speedometer and odometer has basically stopped working. After a long period of time driving the problem seems to fix its self but after sitting for all night the problem re-appears.

I've noticed my rear axle seals are leaking on the ABS rings so those will need to be replaced as well. Does anyone have the EWDs for this year? I'm not sure what year they changed over to an electrical display for the Odometer but it would seem to me this isn't a problem with my gauge cluster and something else.

[SOLVED - See below]

[WWRD99]

I've never been to Moab but what I've heard it's very dusty, sandy and such, being your axle is leaking oil it may have combined with some sand or other stuff and clogged up a wheel speed sensor in the back...the speedo runs through the abs to the cluster...it may work if you take out the speed sensors in the rear axle and spray them down with a cleaner...probably take the drums off so it won't go on your shoes...if you want...if there is a ton of axle oil it might get on them...you may have cut a speed sensor wire too...take a little looking to make sure.

[APhelps]

Originally Posted by WWRD99

I've never been to Moab but what I've heard it's very dusty, sandy and such, being your axle is leaking oil it may have combined with some sand or other stuff and clogged up a wheel speed sensor in the back...the speedo runs through the abs to the cluster...it may work if you take out the speed sensors in the rear axle and spray them down with a cleaner...probably take the drums off so it won't go on your shoes...if you want...if there is a ton of axle oil it might get on them...you may have cut a speed sensor wire too...take a little looking to make sure.

This doesn't appear to be a problem because of a few reasons after looking it over. The ABS speed sensors tie into the ABS control module and I'd expect the ABS module to throw codes if the sensors were not working.

I'm having some difficultly understanding how the heck Toyota drew up the wiring diagram from the ABS ecu -> speedometer -> ECU. The transistors appear to have diodes in front of them which would imply signal direction.

[APhelps]

Pulled the ABS ecu out and didn't notice anything wrong with it. Perhaps I should pull out the gauge cluster and probe the wiring to make sure all the wiring from the ABS -> Speedo -> ECU is still good this weekend.

I'm confused though since it looks like from the speedo to the ECU is really ECU -> Speedometer given the diode in the ECU. Perhaps someone drew it in backwards by chance? There's certainly some minor mistakes in the FSMs.

[MaineRunna]

I think your 98 uses a VSS (vehicle speed sensor) located on the transfer case. I believe Toyota went to the 4th gen style ABS system which uses ABS sensors for the speedo in 2001. I just went through this on an 01 and it turned out to be a failed ABS module. (very expensive)

[WWRD99]

It won't throw a sensor code if the voltage for that sensor is ok...it may not be reading the tone wheel correctly is what I'm getting at...not sure if you have a reader that gets into the abs but current data will show the 4 speed sensors and the vehicle speed when driving...would eliminate input problems to the abs pcm if you have any.

Sent from my SM-G955U using Tapatalk

[APhelps]

Originally Posted by WWRD99

It won't throw a sensor code if the voltage for that sensor is ok...it may not be reading the tone wheel correctly is what I'm getting at...not sure if you have a reader that gets into the abs but current data will show the 4 speed sensors and the vehicle speed when driving...would eliminate input problems to the abs pcm if you have any.

Sent from my SM-G955U using Tapatalk

I'd have to buy a better code reader than I currently have (which isn't a terrible idea).

It is my understanding that as long as two of the sensors are functioning the speedometer will still work so I'm having a hard time believing that my ABS wheel sensors are at fault without throwing any codes.

Looks like I'm stuck between buying a new code reader or swapping in a ABS module and then possibly a gauge cluster and seeing what happens. I'd just hate to buy a new code reader and find out that for my 1998 it won't actually be able to pull the data to the code reader leaving me right where I am.

Seems like my ECU is fine though given the speedometer isn't working and my ECU is throwing codes.

[WWRD99]

Guess I'm lucky on the scan tool since I got a mt2500 snap on scanner new...in 98...costed more that most cars at the time and it does tap into the abs...I have that basic blue tooth thing that hooks to my phone that does show vehicle speed...that should show up in the engine side...so if that pid is getting input from the abs it should show sensor speed...it does the GPS speed too...what I'm thinking is...the abs is showing speed at say both front sensors and the tcase speed sensor but one in the back is giving no input...so with an input missing it shuts down the system...I'm thinking since it's shifting ok (I think)the tcase sensor is ok...I can't recall if the rear sensors are 2 wire or 3 wire...the 2 wire are very basic and the PC won't know if a sensor is bad or the tone ring is the problem...a 3 wire the PC will know if the sensor is bad as the 5 volt vref makes the sensor live and not passive...I'd try the basic scanner it sounds like you have and see if you can see vehicle speed pid...its one of the ob2 mandates so it's in there somewhere...getting a scanner that does abs is nice...I've seen some that cost 150 to 200 ish...like 2 hours diag at some shops...nice thing is you can use it on another car later.

[SaulG]

P0500 is no VSS to ECM .. does CC work?
Check all Fuses?
Speedo Cable? The Vehicle Speed Sensor feeds the ABS ECM. ABS WSS codes usually in the 30's

[APhelps]

Originally Posted by SaulG

P0500 is no VSS to ECM .. does CC work?
Check all Fuses?
Speedo Cable? The Vehicle Speed Sensor feeds the ABS ECM. ABS WSS codes usually in the 30's

I've been utilizing the wiring diagrams found here : Dropbox - 1998 4Runner Electrical Wiring Diagram EWD319U - Simplify your life

The CC isn't going to work if the speedometer isn't working. P0500 is no VSS to the ECM/ECU (whatever you want to call it). Which indicates to me that the ECU/ECM is totally fine.

I'm not throwing any ABS codes, I've even jumpered the terminals in the diagnostic port and my ABS light just flashes continually as it should.

My understanding is that the speedometer works off a current bias and the fuse for the circuit also powers such lights as the OD on/off in the gauge cluster (among a few others).

I pulled the ABS module off the vehicle, opened it up and didn't notice anything that looked bad. I'll probably pull the gauge cluster off tomorrow morning and see if anything is damaged. At that point I'll probably probe the wiring to see if the wiring is within spec as well.

People in later years have had ABS module problems and a few with the gauge cluster. It seems like i can pick up the module and gauge cluster in a junkyard for 50-60 dollars so that's probably what I'll do and see what happens.

[APhelps]

Checked the wiring from the fuse -> gauge cluster, checked the wiring from the abs module -> gauge cluster, checked the wiring from the gauge cluster -> ecu and checked gauge -> ground. All the wiring checked out fine.

Got a gauge cluster from a junkyard and swapped the new speedometer / odometer to the old gauge cluster and still didn't work. Swapped the new speedometer / odometer with the new gauge cluster and it worked. At that point I swapped the old speedometer / odometer to the new gauge cluster and it worked. Looks like the printed circuit board was the problem.

I don't see any damage on it so I'm still sorta scratching my head on where exactly it broke/went bad.

[phattyduck]

Originally Posted by APhelps

I don't see any damage on it so I'm still sorta scratching my head on where exactly it broke/went bad.

I had something go wrong with my gauge cluster flex PCB with no visible damage, so it can happen.... a broken trace is the likely cause. (mine was with the tail/turn/reverse lights)

-Charlie

[APhelps]

Originally Posted by phattyduck

I had something go wrong with my gauge cluster flex PCB with no visible damage, so it can happen.... a broken trace is the likely cause. (mine was with the tail/turn/reverse lights)

-Charlie

Interesting. I pulled some of it up looking to see if I could find a broken trace but did not. After pulling out the speedometer and odometer it does seem like if one is ever to go bad you can fix it with some routine soldering. I'm a big fan of keeping the original odometer on the vehicle.

[Jabob]

This “how to” video may be a possible solution...
How to fix Toyota Lexus Speedometer and Odometer that is not working with Erratic Shifting - YouTube