VSS Vehicle Speed Sensor Wiring

[Discdevil]

Hey :]

My Speedo is dead:

pin 1 on the VSS connector reads 12v. 

pin 2 is connected to ground. 

pin 3 reads 9v (signal wire)

 

 

I have connected a simple OBD II scanner to the car and selected VSS and graphed it to see if i get any change when quickly tapping 12v to the signal wire when jumping the two wires however, the obd scanner reads 0. considering the continuity to ground is good at the connector and the power to the connector is good and simulating the sensor by jumping the power pin to it repeatedly i can summize that the problem lies between the signal wire and wherever it connects to. 

my question is , where does it connect to? some people say the dash, others say the ECU. i have ordered a haynes manual however, it hasnt arrived in the post yet so i dont have access to wiring diagrams. 

does anybody know where the signal wire from the VSS sensor connects to in the car so then i can check continuity?

 

Thanks , Luke.

 

 

[Discdevil]

Update, i have an ABS light. 

Using the SST check wire. i have two codes. 

31 & 35. 

does anybody have a DTC chart for SST?

[Discdevil]

Using the website below, i have found the SST DTC codes. 31 refers to right front wheel speed sensor is malfunctioning. while 35 refers to an open in either the left front or right rear. 

When i have some daylight, ill diagnose this further and update you guys. 

Quote

http://www.testroete.com/car/Toyota/mr2 spyder/References/Technical Training/05 - Brake Systems/20.pdf

 

[Devon Aygo]

It has been seen before where water ingress has affected a plug in the RHF footwell this can stop the speedo from working and store fault codes.

In the RHF footwell behind the kick panel trim ( right of throttle pedal ) is a large square plug with a bolt head in the centre undo the nut to release the plug and check fro green/corroded plugs. This plug passes all the signals coming into the cabin through to the dash and ECUs and if corroded causes lots of niggles in the dash electrics, if green/corroded clean,dry and repair as needed and locate and stop the water ingress.

See: 

 

 

[Discdevil]

1 hour ago, Devon Aygo said:

It has been seen before where water ingress has affected a plug in the RHF footwell this can stop the speedo from working and store fault codes.

In the RHF footwell behind the kick panel trim ( right of throttle pedal ) is a large square plug with a bolt head in the centre undo the nut to release the plug and check fro green/corroded plugs. This plug passes all the signals coming into the cabin through to the dash and ECUs and if corroded causes lots of niggles in the dash electrics, if green/corroded clean,dry and repair as needed and locate and stop the water ingress.

See: 

 

 

Thanks for your reply however, the connector block i have in my 2003 swb rav4 doesnt look like that. I did take the connector blocks out in the drivers side foot well and checked them. They looked fine. 

I received the techstream device today and found the following two codes. 

 

I have also uploaded a video of the car moving with the right wheel sensor not providing any data. (this could be a wiring problem or a speed sensor problem) although it would be nice to know where the connector block is for the sensor inside the drivers compartment so i can run a continuity test from that connector to the speed sensor wire next to the wheel.

 

 

 

[Discdevil]

So i have connected the FL speed sensor to the FR speed sensor harness. 

I spun the left wheel and got a reading on the right wheel which is good. it means the wiring the the ECU is good.

3 of the wheel sensors work, i take it if even a single sensor is down the speedo goes down? Also there is a VSS on the back of the engine... so all 5 sensors need to be working for the speedo to work?

 

 

[Discdevil]

Following my diagnosis; I took the ABS sensor out to test it when saw that it was very dirty. on further inspection the tone ring was loose and had cracked so ive ordered a new one. i'm still not entirely certain at this point this will fix the speedometer as it surely cant be the case that the car needs all 4 sensors working to determine speed as 3 of them were working. 

When i replace this reluctor ring, ill test to see if it fixes the speedo. if not, ill have to test continuity to the back of the cluster from the VSS on the engine block which i know wont be fun since the wires are all colour-coded white in the cluster and i will have to rely on pin numbers.

 

 

[Discdevil]

update, still not fixed...

I have purchased a new abs ring and fitted it, the wheel sensor works and the abs light does not come on so problem fixed there.... however, this is an independent problem to the speedometer not working. 

i have taken the speed sensor out and tested it and it cycles between 12v and 0v as it should. 

When it is plugged into the cars harness i see 12v at the sensor & signal wire however when spinning it manually; it doesnt change to 0v which says to me the problem is the grounding in the circuit....

i have probed pins A4 and A6 on the instrument cluster and they have continuity between A4 and pin 3 of the sensor. A6 has continuity to pin 2 on the sensor which rules out a broken wire to the cluster. 

as a matter of interest i spliced and grounded pin 2 of the sensor to Battery negative with everything still connected to the harness and span the sensor manually which showed the 0-12v pulse width modulation i wanted however, still no response from the speedo. i would like to say at this point it must be the cluster which is faulty however if the speedo only works unless the grounding current runs though it rather than an arbratary ground i made to Battery negative then of course it wouldnt work so im suspecting a bad ground connection after the cluster however, i dont have a wiring diagram of the cluster which would be really useful if anyone has one on here. 

the only way forward from here is to either find a instrument cluster diagram so i can trace which pin the ground current comes out of the cluster after going into pin 6 to check the grounds or just buy and swap out parts to rule out the cluster which isnt very scientific :p

 

any suggestions or wiring diagrams peeps?

[Discdevil]

Another update... it doesnt look like the cluster is the problem.

I plugged the sensor in and manually span and no speedo movement 

i tapped the signal wire to ground and nothing happend.

i turned the sensor slightly until it read 12v and THEN tapped the signal wire to ground and then the needle moved on the speedo. 

I can see that the meter readings actually read 12v - 3.6v -12v etc so it doesnt actually go to 0V which may be the problem, it looks like the sensor is outputting a bias voltage of 3.6v and then a square wave of 12v to 3.6v which isnt low enough for the op amp in the cluster to register it as a "low" causing no speedo movement at all. 

i have ordered a new VSS and i will see how this oscillates before i install it to confirm my theory.

Very weird speed sensor problem indeed. since i took my instrument cluster apart i need to re-calibrate my needles now haha :p fun times.

[Discdevil]

update. ive confirmed my findings. it is indeed the speed sensor. i have tested a new one and it works fine when turned manually with key on engine off. hope this helps someone else with a similar issue.