Syvecs Forums

Removing LamV, and giving it 5V, does not change the reading in SCal at all (still 2.5V).

Weird indeed.

I'm, not 100% sure this is a valid test?

I have an ECU on the bench and just applied 5V to the LamV pin, and also see no change from 2.5V. Lambda sensors don't actually generate a 0-5V signal - they produce a current that will be turned into a proportional voltage, which is what SCal is reporting.

Nevertheless, it does all point to the ECU being faulty, as long as you really really are 100% sure of your wiring and the cal setup!!

TimH wrote:I'm, not 100% sure this is a valid test?

I have an ECU on the bench and just applied 5V to the LamV pin, and also see no change from 2.5V. Lambda sensors don't actually generate a 0-5V signal - they produce a current that will be turned into a proportional voltage, which is what SCal is reporting.

Nevertheless, it does all point to the ECU being faulty, as long as you really really are 100% sure of your wiring and the cal setup!!

My bad, I thought there would ahve been some change on the input pin doing this, although isnt something I've ever had to try.

The NTK UEGO sensor consists of two Nernst cells, one sensing cell and one ion pumping cell. The theory of operation is that one aims to maintain a stoichiometric reading by pumping ions into or out of the sensing cell using the ion pump cell. The amount of ion pumping is controlled by the current supplied to the pump cell. The appearance AFR is then determined by measuring the pumping current by means of a transimpedance amplifier. In this case it is biased at 2.5V for no current and will go up or down depending on the direction and magnitude of the pumping current.

If you connect 5V to the sense signal, then the error amplifier will try to correct this reading by sourcing or sinking current through the LAMI pin, but if that pin is not connected to anything then there can be no current flow and hence with no current, there will be no change to the 2.5V bias of the transimpedance amplifier. If a resistor was connected from LAMI to LAMGND then you would see a voltage develop across the resistor (due to the current) and also you would see the 2.5V output of the transimpedance amplifier change as it is now able to measure some current.

Hope this helps / makes sense,

Pat.

More than 2 years later, I better update this for the benefit of other users. I RMA'ed my unit, and Syvecs found a blown resistor in the lambda control circuit. No idea how that could have happened, but after they fixed it the lambda is finally working correctly.