Agathe said:
land rover 01 discovery 63k miles.
i heard it is the o2 sensor too from auto mechanic. He checked it with his little computer thing but he needs further tests to make sure. Futher tests cost money so I said no.
I gotta pay 200 and my warranty will pay for the rest but I don't think I can afford it right now so I will drive around for another week or so. Hopefully it doesnt blow up.
If he checked it with the "little computer thing" and it said it's a bad O2 sensor, there's really not much more to check. Those computers scan the car's computer (here on out known as OBD2 system) to see what trouble codes it's flashing. The OBD2 system manages all of your fuel and spark, analyzes your exhaust to figure out if you're running rich/lean, it's a good thing.
When there's a problem, the OBD2 system finds it and stores that problem in the computer. Then the check engine light comes on. Once the check engine light comes on, you're supposed to go get the car computer scanned, which your mechanic obviously did. The mechanic read the trouble code (bad O2 sensor) and if that's the only code the computer gave him, then that's the problem. There should be no further diagnosing needed if there were no other codes. However, you need to know whether it was the 1st or 2nd O2 sensor. There should be 2 and 2 only, one between the engine and the catalytic converter, and one after the catalytic converter. Unless you know which one is blown, you'll be replacing 2.
Honestly, yes, a die hard technician is going to tell you that further testing is needed because they want to replace the O2 sensor, run the car for a while, and then make sure nothing else is wrong. There also is a possibility that after the O2 sensor is replaced, something else could be going bad that caused the O2 sensor to spit out a code then you'll get another code...etc. It's not a high probability, IMO.
Of course, you're also dealing with Land Rover and I've heard nothing good about their mechanics. Friends of ours had one and they were having major issues. First land rover told them they had a bad cylinder. Then land rover told them they had 2 bad cylinders. Then land rover told them they needed a whole new engine. In the meantime, they were asking me if I could do an engine swap for them (to which I said it better be worth it and you better have a garage as well as be renting me an engine hoist and a stand). Finally they took it to another mechanic who found the problem....2 stuck valves. 2 stuck valves |= engine replacement. There was no damage to the pistons (I think the valves were stuck closed). A couple hundred, not thousand, dollars, they were problem free.
If the mechanic says it's a bad O2 sensor and that's what the computer said, he really can't be blowing smoke up your ass on that one. It's an easy fix.
Whoever said reset the computer (I don't feel like checking) that's not really a great solution. It's not going to do anything when you've already got a blown sensor unless the OBD2 system is bad anyway, in which case you need to replace the OBD2 system. All that will happen is the O2 sensor will tell the OBD2 system again that there's a bad O2 sensor and you are back at square one.
Also, and this is very important if you live in a state that has emmissions testing, NEVER, EVER, EVER reset your computer before going for an emmissions test. They are going to tell you to leave and come back in a week after you've driven the car around. Why? Because the OBD2 system will tell their emmissions computer right away that it was reset and has not had a chance to run through it's paces, therefore it can not verify that all emmissions systems are functioning properly. It might work for an OBD1 equipped car, but not an OBD2. No way, no chance, no how. Trust me, a close friend has every PA Emmissions certification and he's seen it happen a bunch of times. If the customer returns, they end up finding out that their OBD2 system had found a problem, but the customer thought he/she could get away with it by unhooking the battery to reset the OBD2 system.
I think the mechanic's OBD2 system scan can reset a blown sensor code without resetting the entire system, but I'm not sure on that. The codes still need to be cleared after you replace sensors, and the last time I had to replace a sensor on an OBD2 equipped car, I ended up pulling the fuse for the system to reset it fully. Check engine light never came back on, as I had corrected the problem (replaced a bad O2 sensor).
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