Yaris 99 Gs Mil Problem

[James Watts]

Basically, my orange "malfunction indicator lamp" came on the other day.. This has happened before and i just reset it disconnecting the Battery.. 4 months later its come back on.. only when weve been on high speed roads. I joined two connectors together on the diagnostics socket to get the MIL to flash and decoding this, i found out it was Fault Code 25. I had a look on google for toyota fault code 25 and on two websites it says "25: AIR/FUEL RATIO LEAN INDICATOR--LEAN SIGNAL SENT TO ECU FROM O2 SENSOR" Is this a fault with my sensor? ive had the same exhaust for 11 years and have a feeling that the sensor is clogged up with carbon.. The cars done 68000 miles aswell. I had a look for the sensor and i found two on the exhaust pipe, one in the engine compartment and one just under where the gearstick is.. Are these both o2 sensors and do you think i should replace the 02 sensor? Any advice is much appreciated!

[Davax]

Yes the sensors on your exhaust pipe are both Oxygen sensors. One is fitted prior to the Catalytic Convertor and the other after it. First you should check the wiring contacts. Both should have a wire coming out of the sensors and a connector at the end of these wires. Check if any of the wires are broken and if connectors need cleaning. Then remove the Battery terminal and connect it again to clear the code. See if the Mil lights stays on again. If it does stay on then you have to remove the O2 sensors and check them out. If they are corroded or look damaged then you have to replace them. If they look ok then you may try and clean them. Fill a Jar with some gasoline and put the sensors in it. There should be enough gasoline to submerge the lower O2 filter. Leave it overnight and clean it with paper towels in the morning. Reinstall them and again disconnect Battery and reconnect and check if the MIl stays on again. If it stays on then you have no alternative but to replace these sensors. The problem is you wouldn't know which one of the sensors is actually faulty unless you use a code reader / scanner. But it would be a wise idea to replace them both since both of them have taken the same amount of torture in the exhaust pipe.

Good luck

[James Watts]

Thanks for the reply.. Il do that sometime this week and let you know how it went