Replacing oxygen sensors...
 

Hello All and Disco Mike,

My 2000 Discovery just failed the emissions inspection for NY State. The failures that came up were related to the O2 sensors. What I'd like to know is exactly how many O2 sensors does this truck have ? Is it just front and back ? I have the workshop manual and it refers to them as "post catalytic heated oxygen sensor" and "pre-catalytic heated oxygen sensor." That's the only two entries I found in the manual for Oxygen sensors. Also, I took the car to the dealer last month and they told me I had to replace the Mass Air Flow Sensor. Could that be causing the Oxygen sensors to malfunction ? And could you also recommend a website for purchasing O2 sensors and a mass air flow meter ? Thank you. - ITMagician

RE: Replacing oxygen sensors...
 

How many miles on your truck, is your check engine light on, what faults by numbers do you show?
Mike

RE: Replacing oxygen sensors...
 

I just bought a pair of front sensors for my 2000 Series II for $53.ea. on ebay. These are factory parts. The sellers ID is roversavings.

Willie

RE: Replacing oxygen sensors...
 

Why don't you send me your tele number and a good time to call. I'll call you and we can talk about the MAF and O2 sensors.
Mike

RE: Replacing oxygen sensors...
 

I got the O2 sensors today in the mail. They are aftermarket units not genuine like in the picture.I think they are denso. They have the same plug so they should work fine. I have to go through emissions next week so I hope they work.

Willie

RE: Replacing oxygen sensors...
 

After changing sensors do you need to clear the codes or will they clear automaticly? The service engine light is on with codes P0733, P0734, P0174, P0171, P0154, P0155. I took the airflow sensor out of the MAF housing with a security torx bit and cleaned it with CRC electronic cleaner. If that doesn't work, Atlantic British sells a replacment sensor for $90 without the housing.

Thank you,
Willie

RE: Replacing oxygen sensors...
 

Willie,
Go down to your local auto parts store or shop and have them clear your codes, the ECU won't automaticly clear them.
Mike

RE: Replacing oxygen sensors...
 

I went to the parts store and they cleared my codes. The service engine soon light went off. About 40 miles later it came on again. So I went back to the parts store to read the codes. The codes are;
P0174 system too lean(bank 2) ,
P0171 system too lean(bank 1).

After changing the frontO2 sensorsI am no longergetting the codes;
P0733 gear 3 incorrect ratio,
P0734 gear 4 incorrect ratio,
P0154 O2 sensor circuit no activity detected(bank 2 sensor1),
P0155 O2 sensor heater circuit malfunction(bank 2 Sensor 1)

Do I need a new MAF? Thank you foryour help. Emissions test is needed soon so I need to figure this thing out.

Willie
2000 Discovery II

RE: Replacing oxygen sensors...
 

All,
I have had the same problem that returned the same error codes. The fix for me was to unhook the airfilter hose from the fuel injector and blow it out with some degreaser. This got rid of all the error messages and now my truck works great!

RE: Replacing oxygen sensors...
 

I don't like to correct people but this is truely a bad thing to do, it will kill a MAF quickly and the engine won't like degrease going thru to the O2's that can become fouled.

Willie
Send me a PM and give me your tele number, sounds like we need to talk.
Mike