[ZionXIX]

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January 2018 update: SOLVED

I installed a used ABS ecu at the passenger kick panel and the P0500 cleared instantly and my odometer is now working.
If you have this OBD-II code, open up your ABS ecu and look for melted capacitors.

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So the other day I started her up and the took off without a second thought and noticed that the speedometer was not working.
Pulled the OBDII codes and got "P0500" = Vehicle speed sensor malfunction.
I tried to do some research so as not to waste the forums time with lazy repeat posts.
In my defense i cannot access the following posts:
ABS light

ABS Unique Problem

The connection times out so Im not sure what to do with those.
Google doesn't even give me the "cached" option for those pages.

I dont know if the 1996 2WD model gets speed information from the ABS sensors or a transmission speed sensor.
I saw lots of posts about a VSC problem in 01 02 models, but I dont think those apply to me.

First thing i did was check the ABS sensors. 3 of them are reading around 1750 ohms.
The last one was completely severed at the sensor location before I bought the truck and
I never had a problem with the speedometer until now.

Second test I did was jumping the "E1" and "Tc" pins on the engine bay diagnostic box.
When i did this before, I got the code for the right front ABS sensor (The broken one).
Now this new problem with the speedo has resulted in the ABS light not coming on at all during this test.
Instead the cruise control light starts blinking followed by the Airbag light a few seconds later. I'm stumped.
If there is a transmission speed sensor, I have been unable to find it so far.

Any insight would be greatly appreciated.

[phattyduck]

*If* you have ABS, your truck should use it for the speedo. Where was your truck originally delivered (US, or somewhere else)?

Does your speedometer still work?

The ABS system uses the wheel speed sensors, sends the signal to the gauge cluster, which then sends a modified version to the ECU.

-Charlie

[ZionXIX]

This is a US truck with ABS on board. Speedometer is not working. All other instrument gauge are functioning normally. Are you saying there is no Vehicle Speed Sensor on the transmission? Also what is with the weird blinking of the cruise/airbag lights? If it were solely an ABS issue I would expect the (E1/Tc) jumper to direct me to an ABS problem.

[phattyduck]

ABS computer (on the pre-'01 trucks) doesn't communicate with the ECU, at least not for DTC's, I don't think.

No speedo = no signal to the ECU for vehicle speed. No speedo is caused by the ABS issue.

Solve the ABS issues and the ECU code will go away and your speedo will start working.

Now's about the time TheDurk should show up with info on how to debug the ABS and Airbag systems...

-Charlie

[ZionXIX]

So I started investigating the Vehicle Speed Sensor. Its also know as the "No. 2 Vehicle Speed Sensor". It does exist! I found it attached to the transmission about 8 inches away from the drive shaft connection and right above some kind of bushings shock absorber thing for the transmission. It was caked in oil. I unplugged it and found oil inside the connector. Cleaned it thoroughly and tested the resistance at 660 ohms, well within normal range. Afterwards the CEL went away immediately but still no speedometer. Its really unusual because the Speedometer died at the same time as that CEL popping up. If the ECU is happy about the VSS, why isnt the speedo?

Jumped the ABS and still getting the blinking "Cruise" and "Airbag" lights instead of the ABS codes. I also cleaned two factory grounds on the driver side under the dashboard and 1 diy ground going to an aftermarket remote system I didnt know about. I would like to investigate the ABS system some more but Im not sure where to start.

[ZionXIX]

Video of the DTC codes:

(Volume warning)

[phattyduck]

Originally Posted by ZionXIX

So I started investigating the Vehicle Speed Sensor. Its also know as the "No. 2 Vehicle Speed Sensor". It does exist! I found it attached to the transmission about 8 inches away from the drive shaft connection and right above some kind of bushings shock absorber thing for the transmission. It was caked in oil. I unplugged it and found oil inside the connector. Cleaned it thoroughly and tested the resistance at 660 ohms, well within normal range. Afterwards the CEL went away immediately but still no speedometer. Its really unusual because the Speedometer died at the same time as that CEL popping up. If the ECU is happy about the VSS, why isnt the speedo?

Jumped the ABS and still getting the blinking "Cruise" and "Airbag" lights instead of the ABS codes. I also cleaned two factory grounds on the driver side under the dashboard and 1 diy ground going to an aftermarket remote system I didnt know about. I would like to investigate the ABS system some more but Im not sure where to start.

That speed sensor is used ONLY by the shift logic to determine the output speed of the transmission. It does not drive the speedometer - the ABS system does.

If you had a non-ABS truck, then the VSS used for the speedo would be in place of the plug just behind the one in your picture.

-Charlie

[ZionXIX]

Originally Posted by phattyduck

That speed sensor is used ONLY by the shift logic to determine the output speed of the transmission. It does not drive the speedometer - the ABS system does.

If you had a non-ABS truck, then the VSS used for the speedo would be in place of the plug just behind the one in your picture.

-Charlie

You can understand my confusion, they occurred at exactly the same time. Do you know if the VSS is independent of the ABS? or does it tie into the ABS before making its way to the ECU. Because of the course the CEL popped up again today.

[phattyduck]

Originally Posted by ZionXIX

You can understand my confusion, they occurred at exactly the same time. Do you know if the VSS is independent of the ABS? or does it tie into the ABS before making its way to the ECU. Because of the course the CEL popped up again today.

The ABS system is the "VSS" on ABS 4Runners.

So, ABS system gets the signal from all 4 wheels, processes that, sends the signal to the gauge cluster. The gauge cluster conditions that signal and sends that signal to the ECU. If the ABS system is not working, then there will be no speedometer either - and the ECU will throw codes for the VSS.

If you reset the ECU while messing with that sensor, it will take a while to throw the VSS code in the ECU. There is generally some multi-trip logic before that CEL code trips.

-Charlie

[ZionXIX]

Originally Posted by phattyduck

The ABS system is the "VSS" on ABS 4Runners.

So, ABS system gets the signal from all 4 wheels, processes that, sends the signal to the gauge cluster. The gauge cluster conditions that signal and sends that signal to the ECU. If the ABS system is not working, then there will be no speedometer either - and the ECU will throw codes for the VSS.

If you reset the ECU while messing with that sensor, it will take a while to throw the VSS code in the ECU. There is generally some multi-trip logic before that CEL code trips.

-Charlie

I actually never reset any of the codes. All I did was clean and test the VSS and the CEL went away immediately. So puzzling to me. Anyway I'm looking into the ABS now that I have the proper wiring diagrams.

[ZionXIX]

Thanks to TheDurk for providing me with some year specific wiring diagrams. In regards to my wiring problem when jumping the "Tc + E1" on the Diagnostic port. I noticed in the manual it shows that the "Tc" pin is connected to the ABS ecu, Airbag sensor, and the Cruise control. Is it possible that this is my problem? Could there be a wire short to ground in the Tc circuit? I also noticed that the Diagnostic port (aka Data Link 1) has a pin labeled "Ts" specifically for the ABS ecu and a pin labeled "TE1". Can these other pins be jumped to read DTC codes?

[ZionXIX]

Im trying to track down the three components connected to the "Tc" pin on the diagnostic port. According the FSM those three components are the ABS ecu, Cruise control ecu, and the Airbag Sensor Assembly. I found the ABS ecu in the passenger kick panel. The cruise control ecu I found behind the ashtray underneath the radio. The FSM says the airbag sensor assembly should be in the same area as the cruise control ecu. I dont see anything in there labeled for the SRS system. Strangely enough there is also a box labeled ">ABS< Antenna Relay". Never heard of that one. So has anyone actually laid eyes on the airbag sensor assembly?

[Magmotor]

Originally Posted by ZionXIX

So has anyone actually laid eyes on the airbag sensor assembly?

maybe this will help...
https://partsouq.com/en/catalog/genu...&uid=254558&q=

[ZionXIX]

Originally Posted by Magmotor

maybe this will help...
https://partsouq.com/en/catalog/genu...&uid=254558&q=

Thank for that! Its perfectly hidden behind the cruise control covered with some kind of vinyl sheet material caked in dust which provides further camouflage.

[phattyduck]

Originally Posted by ZionXIX

Strangely enough there is also a box labeled ">ABS< Antenna Relay". Never heard of that one.

ABS in that case is for Acrylonitrile Butadiene Styrene Plastic, the material the case is made out of... Not Anti-Lock Braking System.

-Charlie