California officers plug into your car to see how illegal you are? - PeachParts Mercedes-Benz Forum

pentoman · #1 08-15-2002, 08:26 PM

I've just attended a Bosch course for independent techs on Lambda sensors.

They measured lambda values by connecting to the OBD on-board-diagnostic socket, which can double as a 'CARB' plug, which is California..something..something.. The speaker said it could be used by officers if they find your car has bad emissions, to plug into your car and see for how many days this has been the case, and fining you accordingly.

Is this scheme in operation in california? What happens if you say, remove the diagnostic plug fuse, or the wires for the earth pin (4/5) so the plug doesn't work. Can they not fine you?!

For the record:
The lambda sensor's main purpose is to reduce emissions. It measures the amount of oxygen in a car's exhaust gases and adjusts the fuel/air mixture to compensate. If its voltage is low, the ECU sees this and richens the mix (longer injection duration) and vica versa if voltage is high, to get the perfect mix for clean combustion.

When working ok, and on constant throttle/idle, the sensor should alternate between high and low voltage around once a second (it is a simple device with no state for 'mix is just right').
Under acceleration, the ECU ignores it and adds more fuel, so in this case the sensor would be 'high' for too much fuel.
I won't go into more detail

Have the techs on the board had training on lambda sensors? (FTR we also looked at the new 'Planar' ones, which work very differently, demonstrated on a 2002 Audi A4 2.0 20v)