Reducing 12v DC to 0.5V DC no more than 1A draw

[AdCNC]

Hi Irving, yes the o2 sensor should normally output a oscillating voltage but the post cat should see a fairly stable voltage as it thinks the CAT is working and giving a stable O2 output. Is just to clear things up could you do a diagram so I don't balls things up please?

[m_c]

Irving, automotive petrol lambda sensors take a direct output from the sensing element so they output a varying voltage.

Post cat sensors still change occasionally, although I'm not sure how much the ECU monitors their performance, so even by applying a steady voltage faults may still get set.

Another snag you may have to allow for is some ECUs control and monitor the Heater section, so you may need to add a pretty beefy resistor to apply a dummy load to avoid any faults relating to the heater circuit.