I'm trying to read the Vehicle Speed Sensor (VSS) on my 2005 Honda Accord from the cruise control port (port 14P, located behind the steering wheel)--when the cruise control unit is not attached.

With the cruise control unit attached, the VSS toggles between 0~4.5V. When the cruise control unit is not attached, it only reads between 0~0.02V (and is too noisy to be useable). So it appears something in the cruise control unit is informing the ECM to relay the signal?

Below are the 2005 Honda Accord cruise control system and wiring diagrams. Pin 12 is the VSS from the ECM.

If anyone has any ideas or suggestions I'd really appreciate hearing them! Thank you.

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  • Where's this 14p terminal in the diagram? The ECM should be sending the VSS signal to pin 12 on the CCU whether it's plugged in or not.
    – Ben
    Aug 9 '16 at 10:25
  • The 14P terminal goes to the cruise control unit (CCU).
    – moof2k
    Aug 10 '16 at 3:36

The VSS input pin is probably pulled high by the CCU. The ECM/PCM VSS output can probably only pull it low. If this is the case, you would expect to see what you are seeing. You could use a 10k resistor to pull the CCU input to 4.5V and then see if it starts to work as you expect, but I wouldn't recommend doing something like this unless you know what you are doing.

  • That was it! Thank you! Connected 10k between VSS and battery supply (pin 4 on the 14P connector) and I can see it toggling between 0-12V. BTW I found this resource to be a helpful explanation of the topic: dangerousprototypes.com/docs/…
    – moof2k
    Aug 10 '16 at 3:35
  • 1
    I wouldn't have recommended connecting it to 12V seeing as it only had 4.5V on it before, you could be taking the transistor that is driving the output outside of its normal working voltages.
    – HandyHowie
    Aug 10 '16 at 7:10

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