02 Sensor question

[PositronicRay]

94 MB SL320 (petrol)

Question for you sages. I ran a diagnostic check and the code or OS sensor pre cat popped up. Peer under the car wiring is damaged and the sensor is not connected, why wouldn't this bring up the engine check (emissions light)

The car has been running perfectly BTW smooth engine and no decernible difference in fuel consumption.

Just curious?

[stevieturbo]

PositronicRay said:

94 MB SL320 (petrol)

Question for you sages. I ran a diagnostic check and the code or OS sensor pre cat popped up. Peer under the car wiring is damaged and the sensor is not connected, why wouldn't this bring up the engine check (emissions light)

The car has been running perfectly BTW smooth engine and no decernible difference in fuel consumption.

Just curious?

Old car, old systems. Sometimes their onboard diagnostics just arent as informative as modern systems.

[anonymous-user]

Back in the day, the MIL was only legally required to inform the driver of failures that caused the vehicle to emit a level of tailpipe pollutants that would fail the mandated drive cycle tests. In 94, with EU2 level emissions limits (huge compared to today!), engines could run "Open loop" and still pass because they did not need to maintain such an accurate control on the fuel mass as they do now.
So, lambda sensor fails, and almost certainly sets an internal error code in the engine ecu, but does not set the MIL.

[PositronicRay]

Thanks chaps.

[AER]

Yes, no OBD required for EU-2. Only EU-3 onwards. I thought Max would remember this, but he is getting on a bit...