Code 21?

[hazchuen]

I just went to check my car and I got a "Code 21:Oxygen Sensor Signal or Circuit fault". Which Oxygen sensor is it on my 2000 RX300 with 1MZ-FE (3.0 c.c V-6) engine?

[MrADeveci]

I believe the oxygen sensor is on your exhaust ............

[hazchuen]

how about on the exhaust headers? how many oxygen sensors are there?

is the oxygen sensor the same as air fuel ratio sensor? if not, how many air fuel ratio sensor are there too?

sorry for asking too many question. i'm a bit confuse here. thanks.

[ColinBarber]

There are two a/f ratio sensors, one on each of the headers, and one normal oxygen sensor after the cat.

You need a better fault code to be able to identify which sensor has the problem. Connect up an ODB-II tool to retreive the P code.

[smiffie]

Dead Cat

[hazchuen]

There are two a/f ratio sensors, one on each of the headers, and one normal oxygen sensor after the cat.

You need a better fault code to be able to identify which sensor has the problem. Connect up an ODB-II tool to retreive the P code.

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got the car on jacks at a servicing workshop and surprise2 they found a crack exhaust header! does this cause the oxygen sensor to flag or the oxygen sensor is really faulty.

[ColinBarber]

It could do as reading may be out of spec to what the ECU is expecting. Or the sensor could have been damaged.

[hazchuen]

change both banks oxygen sensor with O.E.M parts 89467-48011, and it still does not make any difference. what a waste of money. wonder if there is anything wrong with my ecu?

[kitty]

try disconnecting one of the sensors see if anything changes, and then the other sensor and again monitor any changes. not sure about lexus ecu but i'm sure you'll find that you're running too rich if the o2 sensor(s) ain't working - are you using more fuel than normal?

i've found on other cars in the past bad connections which breaking the connection cleaning and re-instating works - cheapest diagnostic check before you spend any money.