I got "Service Engine Soon" light on and P0150 on my 2003 Discovery S7 which has 73k MILES on it. So I followed Mike's direction and changed all four O2 oxygen sensors and all enight spark plugs (used NGK Platinum G-Power). After I used INNOVA CanOBD2 Code Readerclear the code, Istart the truck, the "Service Engine Soon" light went off, and the truckoperates good. I took a ride for about 2 miles, the "Service Engine Soon" light came on again. So I used the code readerscanned again and got the same P0150 code (according to the book, it said "P0150
O2 sensor circuit malfunction (bank 2, sensor 1)
Front sensor RH bank stoichiometric ratio outside operating band"

Any of you experience the same and how to get it resolved?

Thanks!

 

Sounds to me like the Code Reader is telling you exactly what to do. Replace the o2 sensor that is "outside operating band". 02 sensors do not have any adjustments. They either work , or they don't, although.....you could try unplugging it and plugging it back in (the plug in the wire from the sensor), as plug contacts do get corroded.

 

check the wire and plug all seemed ok. and what I changed yesterday was a brand set of new O2 sensor (I got a full set from Motorcar which suppose to be good). don't know whatelse to check next...

 

I agree, check the wires and connection first, sometimes they are dirty.
There have been some 02 wire harness issues, may want to have that checked also.

 

Get some electrical contact cleaner and clean all the connectors.

 

very weird...I checked all connectors they all seemed OK. So drive the truck for another round and came back read the codes again, guess what I got this time:
P0130
P0155
P0150
P0130
P0139
P0141
P0161

according to the book, basically it's telling me that all four O2 sensors are malfunctioning "short/open circuit (NAS and EU-3 only)"

don't know what's really happening...

 

OK, I have heard of this sort of thing before, after new O2's were put in the ECU had to "re-learn". It was used to the old ones and once he drove the trk for a few hundered miles the light shut off and all was good.
The other option is to have the stealer re-set the ECU.

 

The trk still runs, but got the "service Engine Soon" light back on after i drove it for about 100 miles, it seemed using a lot more gas, and the idle is bit rough and the rear end of the exaust pipe was turning black.

used the code scanner again, still having the above 6 code, but didn't show the system too rich code code P0174 or P1174.

Don't know if I should continue to drive it or put the original O2 sensors back to see if it makes difference.

 

I would keep driving it. Once you've hit 500 miles and the ECU re-learns everything clear the codes and the light should stay off.
The black tailpipe is normal, it was black before but you never noticed.

 

Would there be a way like disconnecting the battery terminal that would reset the ECU?

and how I can tell if the new installed O2 sensors are working other than reading the codes?