2007 yaris sedan third plug on wiring harness

[Frankieo]

I'm installing a after market dvd player into my car but there is a third plug going into the stock head unit and I have no idea whats it for I have all the wires hooked up to my new unit but don't know why there is more connectors. I took for a drive and got a check engine light on took it too autozon re and they gave me a code of p0500. Took the car to the dealer and they said that the old radio needs to be connected because that plug sends a signal to the car computer and let's it know that the car is moving. Has anyone came across this problem or know of way to bypass this?

[BLH]

I think they got it backward.

I see a speed signal on Connector D74-3 and I thought it gave the radio a speed signal so it could adjust the volume automatically as you where driving.
The ASL setting on mine determins how much the volume changes with speed.
The other wires in that harness are for the external Aux Input Jack some cars where equipped with.

[Frankieo]

Maybe I said that wrong. Is there a way I can bypass I really don't want to put the old head unit back on.

[BLH]

I am not an expert on this, but from what I have seen in the repair manual. The speed sensor signal goes into the Combination Meter assemble where it feeds the speedometer and then gets sent out to the ECM; the radio and the power steering control module.
The radio is an Input and leaving it disconnected should not stop the signal from going to the other devices.
Does you speedometer work correctly?

[Frankieo]

Yes the speedometer is working fine. I reconnected the stock radio and still the same message pops up on the dash. I'm stumped with this problem.

[CTScott]

The ECM definitely doesn't need the radio to be present to get the VSS signal.

Did you clear the code and it came back? If so, how quickly does it come back on?

[Frankieo]

I unplug the battery to the clear the code. The check engine light congress on right away as sonn as i go over forty miles the engine starts to rub funny the idle drops and the cruise control don't work.

[CTScott]

Did the problem start immediately after you installed the new radio?

[Frankieo]

Yes it did I took the car to the dealer and they said that third plug needed to be connected to the radio and wanted to charge me $230.00 to reinstall the the stock radio and delete the code. They also said that the code might not go away right away Ave may need to cycle to reset by it self. So I took the car back and reinstalled the radio back instead of giving them $230.00. How long does it take the car to cycle the code out.

[CTScott]

Originally Posted by Frankieo

Yes it did I took the car to the dealer and they said that third plug needed to be connected to the radio and wanted to charge me $230.00 to reinstall the the stock radio and delete the code. They also said that the code might not go away right away Ave may need to cycle to reset by it self. So I took the car back and reinstalled the radio back instead of giving them $230.00. How long does it take the car to cycle the code out.

As soon as the ECM is happy the code will clear, or you can clear it with a scan tool. Follow the third radio connector up to the junction block D36, which is mounted to the dash support up above the radio. Check the connector to make sure that the everything looks OK where the white wire from the radio connector comes into that connector. The VSS signal comes into that block and splits there to the cluster, PS ECU, radio, and ECM. Maybe wire got pinched, or pulled when you swapped the radio.

[Frankieo]

Thanks I will look into that do you have a picture of what that may look like?

[CTScott]

Originally Posted by Frankieo

Thanks I will look into that do you have a picture of what that may look like?

It's two connectors with a block in between, that makes the multi-wire junctions:
Conn D36.jpg

[Frankieo]

Thanks!