Puzzled by emissions.

If you unplugged the sensor, and it made no difference to the Pscan, then to me that suggests the ECU is not reading the sensor at all!

As you prooved the ECU is not at fault, then this leaves the lambda sensor and wiring as suspect.

If the ECU can not read the lambda, then the ECU may be in a "limp mode" which the Pscan is reading.


However if the lambda sensor is not heating up, it will output a constant 0.5V (0.49V!!)!

Have you checked the heating voltage to the sensor, the heater resistance, and the sensor output?

I plan to spend some time over the weekend checking wiring, the multimeter will have a beating.

I'll post how I get on.

So I repaired 3 damaged wires in the main loom (1 was an A/C wire to the ECU, 1 was the wire from the boot lock to the 5AS unit and 1 runs between the ECU and the dash panel).

I have also checked the continuity of the wires between the ECU and the probe, all correct.

Not that I profess to be an electrical wizard but I think a sparky once told me that continuity tests are not a sure fire way of eliminating faults in looms as under load a faulty wire will fail . I am sure by now you must be doubting your own diagnosis , I know I would be . Stick with it .
John

sworkscooper wrote: Not that I profess to be an electrical wizard but I think a sparky once told me that continuity tests are not a sure fire way of eliminating faults in looms as under load a faulty wire will fail . I am sure by now you must be doubting your own diagnosis , I know I would be . Stick with it .
John

Quite right if the wire is breaking down,


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The load through the sensor is under 1 volt so is less than the 9v the multimeter is putting through the circuit.

Are the error codes disappeared?
And is O2 sensor correct working now?

I clear them but they come back.

I haven't done another gas test but the scanner still says the sensor isn't working.

I still think that there is something wrong with injectors or poor ignition.
Normaly when there is no lambdasensor signal the ECU switch to basic mode. Fuel trim will go to the basic 100%.
In that case CO can be a litle bit high but not 2 or 3%.
And there should be an error code for lambda sensor. Maybe the description is not correct for the code.