Faulty Lambda Oxygen Sensor

February 28, 2006

First posting - any help will be greatly accepted.

Rav 4 (52 - had from new, always serviced at dealer)

Dashboard light on = faulty lambda oxygen sensor (sensor 1, bank 1)

Local Toyota dealer want £ 265 to replace. A slightly further away dealer said £ 210

When they came to replace it they couldn't undo the bolts stating there was a strong likelihood that the catalytic convertor would be damaged. An additional £ 430 for new convertor, mainfold & gasket.

My questions are

(1) Are we unlucky or are we being taken for a ride ?

(2) What would you guys do ?

Thanks in advance for help.

February 28, 2006

There are now quite a lot of independent garages who specialise in engine management problems and have good diagnostic equipment.

Leading component manufacturers such as Bosch,Lucas etc supply parts for most vehicles.

Best of luck.

February 28, 2006

First posting - any help will be greatly accepted.
Rav 4 (52 - had from new, always serviced at dealer)
Dashboard light on = faulty lambda oxygen sensor (sensor 1, bank 1)
Local Toyota dealer want £ 265 to replace. A slightly further away dealer said £ 210
When they came to replace it they couldn't undo the bolts stating there was a strong likelihood that the catalytic convertor would be damaged. An additional £ 430 for new convertor, mainfold & gasket.
My questions are
(1) Are we unlucky or are we being taken for a ride ?
(2) What would you guys do ?
Thanks in advance for help.

Sorry to say, Oxygen sensors seized in the catalytic convertor are a common problem, so no you're not been taken for a ride....my only thought is, how hard do they try to remove them ,once the warrenty as run out ! :unsure: .

September 22, 2008

There are 2 oxygen sensors on these engines

1 before the cat

1 after the cat (with a special plate on this one)

The pre cat sensor is used by the ECU to control fuelling etc...

The post cat sensor is used by the ECu merely to determine the health of the actual cat itself.

faulty pre cat sensors can cause fuelling issues - such as running too rich (first you'll notice obvious rich petrol smell and the economy will take a substantial hit in your wallet and mpg) you can if you are mechanically competent change the sensor yourself. It may be rusted into the manifold in which case you'll need to skilfully remove it and possible re tap the thread or use a helicoil insert. you could weld up the old mount point and drill and re tap a new one - I have seen that done commonly.

If your post cat sensor is faulty you could choose to ignore it - it could be reporting a fault code as a result of the pre cat sensor being faulty and thus causing the ECU to affect fuelling. Best to change the important one first i.e. the pre cat one. These sensors can be had for anything from £10-£40 - yes really that cheap. you can even get quality platinum ones from the states for about £50 postage included!

you may find after a successful pre cat sensor replacement that the fault code from the post cat may go away. if it doesn't - you may choose to ignore it - but you will need to put your exhaust on to a accurate exhaust gas analyser which should tell you for certain if your CAT has actually bought it ( it might have too as too rich a fuel mixture can destroy a cat in next to no time) and the faulty pre cat sensor could have done just that...

If you are relatively certain your CAT is still healthy you can again cheaply replace the post cat sensor with an OEM replacement again for a lot less cost than a stealership would charge. replacing this one is a bit more difficult because of the mounting plate - again drilling and tapping may be required on badly rusted examples.

Hope all that helps somewhat :)