My friend has a 2002 1.0 Yaris and the engine malfunction light came on. The garage (not Toyota) ran a diagnostic and it was found to be the lambda sensor. However, they don't want to replace the lambda sensor, rather they suspect the exhaust is to blame. The car had a backbox recently but the front section (I believe they Yaris has a 2 part exhaust system)which comprises the catalytic converter and mid pipe is still on the original part and has several holes in it and is blowing. The garage suspect that air is escaping and this is giving a faulty reading on the senosr, hence why the engine management light is on. They say that this section of the exhaust (incuding cat) should be replaced firstly and if that doesn't solve the problem, then the lamda sensor should be replaced. Does this sound logical?