93 Previa 2.4gl Ecu Code 25

[propnut]

I suffered a blown radiator and as a result my vehicle overheated. I have installed a new radiator which is working fine but now the ECU light comes on as soon as the RPM gets to around 2700. The code is 25 which according to the manual is a result of the "mixture being either too lean or rich for a period of 50secs after the previous crank angle". The manual lists quite a few possibilities and so far I have

Checked for possible air leaks

Replaced the coolant temp sensor

Checked the ignition system

Checked for a blown head gasket (no sign of combustible gases in the water jacket, all cylinder show constant compression)

My last check was the front lambda sensor which seems to be the culprit as its voltage does not change irrespective of engine speed. It just sits at 0.1v when measuring the voltage between the blue wire and earth. As these are expensive and I can't really see how the engine overheating could have damaged the lambda sensor I was wondering if anyone has experienced this before or has any suggestions.

Thanks

[propnut]

Ok, well seeing as no-one seems to know anything let me provide an update that hopefully might help someone else in a similar position.

After judicious research I have discovered that it is indeed possible to blow the Oxygen sensor through overheating, if as part of the overheating process the head gasket blows. This allows antifreeze into the exhaust system and the silicon contained in this coats the sensor rendering it useless. Whilst I have up till now assumed my head gasket to be fine this may not be the case. As such I will be stripping the head off.

A couple of thing sto note.

1. Spares are much cheaper on eBay - don't go to the agent.

2. You can actually test a lambda sensor on a bench, in a vice using a blow torch.

3. The Previa motor is a real pain to work on. I used to re-build stock cars and big American V-8's which were 1000% easier to work on than this beast.