1996 Toyota 4runner Speedometer and DTC codes problems

Hello everyone,

I have a 1996 Toyota 4runner SR5 2WD. A few wekk ago I noticed that the speedometer stopped working suddenly and the Check Engine Light (CEL) came on simultaneously. I pulled the codes and found a "P0500" code stored for the Vehicle Speed Sensor. I found the sensor attached to the transmission. It was caked in oil. I cleaned the outside of the sensor and the plug really well and put a multi-meter on it. The resistance is in normal range according to the FSM. As soon as I did that the CEL instantly disappeared but my speedometer is still not working. All other gauges are functioning normally.

I have also had an ABS light active since purchase. I pulled the DTC codes a year ago and retrieved the code for one of the wheel sensors that are broken. That broken sensor has never affected my speedometer function. I tried to pull the DTC codes again to see if any new ABS codes had been generated but I have a new problem. When pulling the codes on this vehicle, a port in the engine bay must by jumped with a metal wire. Instead of the ABS light flashing a code, The ABS light turns off, the "cruise' and "airbag" lights begin flashing ans different varying rates. I am attaching a youtube link for a better explanation.

Things I have done to try and remedy the situation:
Speedo died and CEL came on simultaneously, ABS was already active before this. Cleaned the sensor, CEL went away, speedo still dead. DTC codes refuse to generate ABS codes. I cleaned the ground bolts under the dashboard hoping it was a grounding issue. No change.

Thanks

What the what?!
Those lights certainly don't look like they're conveying any trouble codes!
I don't work on a lot of Toyota vehicles, but I'll see what I can get as far as description of operation for the speedometer circuit. (My Alldata is kinda wacky right now).
Remember, the ohm meter can't gauge functionality of a part. I find many sensors and solenoids that ohm within specification, but are still faulty.

Sorry you haven't gotten a useful reply yet

In the meantime, this may help some:

So I managed to get the wiring diagrams for the 1996 specific model. After mapping out all of the ground locations, I have decided to clean the ground wires associated with the the instrument cluster and the AND ecu. I have had to clean several in the engine bay already due to heavy corrosion from oceanic proximity. I will probably do that tomorrow.

Update: I pulled the ABS ECU out and cleaned the grounding contacts really well. Still no change in previous problems.

I also cleaned the ground for the Diagnostic Trouble code port to no avail. I confirmed that the wire harness grounds for the ABS ECU are getting the proper voltage. Next I plan to investigate the single wire running from the ABS ECU to the Speedometer. It will probably be a few days before I have time to dismantle the dashboard.

Regarding the CEL and speedometer, I bet there is still an issue with the speed sensor. Just because the Engine light goes away, doesn't mean the fault is gone. Look at live data and watch the vehicle speed input. Make sure it's there, and it's clean and accurate. My bet is there is no input to cpu.

As far as flash codes go, good luck Not my forte. Find a good service manual, all I can suggest.

Is this a US model?
All my service info shows a cable driven speedometer. As the cable drives the speedometer, the cluster outputs a 5v square wave to the ECM. (That's as far as I got last night before falling asleep. Damn NyQuil!)
I'm with gjauto on wanting to check live data.

Here’s what I know so far:

“V3” VSS
I was originally looking at the Vehicle Speed Sensor (VSS) on the rear section of the transmission. According to the wiring diagrams, this VSS is labelled as “V3”. It’s a 2 wire sensor connected directly to the ECU. From what I understand its to provide information for the Electronically controlled transmission to help decide on the proper gears to be in.

ABS ecu
This system is connected to the ECU by a single wire and the Speedometer by a single wire. The ABS light is on but I cant pull the codes (refer to the video above).

Speedometer
The Speedometer is connected to the ECU by a single wire and the ABS ecu by a single wire

“V2” VSS
In the diagrams, there is a device labelled “V2” VSS (combination meter). I assume this means that it is attached to the instrument cluster. It has 3 wires. 1 for power and 2 wires connected to the speedometer. 1 of these 2 wires also shares the same terminal connection with the wire coming from the ABS ecu.
I have cleaned all the grounds for these systems and confirmed with a multi meter that they are in fact good grounds.

I think the next step is going to be removing the instrument cluster and trying to verify continuity between the speedometer and the other systems. I have posted on a couple of Toyota forums and no one seems to know anything about this specific dash lights flashing when pulling DTC codes. Unfortunately freeze frame data is non-existent on this island.

The FSM describes a procedure that involves jack the rear end up in neutral and rotating the wheels while watching for a voltage change on a specific ECU pin. It says to look for 4 voltage changes per turn of the wheel. I suppose this would confirm whether or not the “V3” VSS is functioning but doesn’t really help with my current problem.

A lot of manufacturers use only one of the four ABS wheel speeed sensors to drive the speedometer. The ABS module cleans up the signal and uses it to provide the speed input for the speedometer and engine computer it looks like this what you have. As you don't have the description of the operation of the system so don't know what sensor drives the speedometer without a scope you would need to check the voltage output of all four wheel speed sensor in turn. Resistance test on the sensors can be mislealeading.

It's good to know that not all speed sensors are needed for the speedo to function. That's probably why it continued to work with 1 destroyed sensor. Researching some more last night, I noticed that in the Data link port I normally jump the Tc and E1 pins to read ABS codes. This Tc pin is connected to the ABS ecu, the cruise control, and the airbag. If there is some kind of short to ground in that circuit, it might explain the weird flashing I get when try to pull codes from the Data link port. I don't even know where to start with that circuit. The wires basically run the entire length of the engine loom.