caudio51

ECU light went on. I diagnosed it as (0510) a downstream O2 sensor maximum voltage monitor fault and (0707) downstream oxygen sensor fault. I did not fix this right away since I read a few people who had this problem and did not fix it for quite some time.

I had some extra time one day and changed the spark plugs to NGK coppers and cleaned the throttle body. RPMs have gone up not at idle but it seems when I am driving about 40mph. Since that, I checked the ECU again and was given the (0510) code and now (0201) Ignition signal primary circuite fault.

I have a 99 Cali-Spec Max, and I am not sure which downstream O2 sensor to replace. I am also not sure if I have four or three. Best way to find out is to look? Any other way to tell for sure in case I miss one?

My thoughts are I want to repair the O2 sensor(s). Then check the RPM/Idle speed after I reset the ECU. Could the ignition code come from the car running rich due to it being in "open" mode? Just looking for some thoughts about the O2 sensor and that second (0201) code.

Thanks for reading all of that if anyone does.

chenzarino

iTrader: (2)

Downstream O2 Sensor does not effect the ECU or change the way the car runs. You have 4 sensors, it is the one on the y-pipe between the two headers. Mine has been bad with 0902 Downstream sensor temp or circuit fault for a few months and it has made no difference at all, not even in gas mileage. As for the ignition code, I'd reset the ECU and see if it comes back on.

caudio51

Thanks for the input.