fuelguy

If you've replaced the sensor, then there can only be an issue in the wiring or a connector.

The next easist step is to clean the connector that hooks up to the sensor. 99.9% sure it won't be this, but do it anyway..

After that, I would start by unplugging the battery(s) again, then disconnecting the ECU plug and reconnecting it about 10-20 times just in case the connection there is crappy.

Failing this, then I can only recommend a Toyota specialist, but be prepared to grab your ankles because it won't be cheap. If I was to trust anyone with my car, it would be Simon at S&B (0433 243 308).

It sounds as though it may be something that you can live with though. I have an engine error code pop up on mine every time I floor it because I have spaced the wategate to increase boost and the error is in the turbo sensor. As long as it comes on only every now and then for a couple of seconds at a time, then I would be inclined to ignore it, but still give Simon a call. He's the guru for the Surfs in WA.

Also, I just noticed the issue with the 4WD light. If you're hearing the system engage, then the first easy fix is to replace the globe in the fascia panel.

Thanks Allen You have been very helpful

Thanks
I have tried everything and the light has gone out but it is still registering 4 flashes on the diagnostic check. The light is coming on but goes out after a couple of seconds.
Next step please.

The turbo fault is now rectified
I have replaced the main temperature sender but the check light still will not turn off. I have tried resetting the system but there must still be a fault.
All help would be appreciated.
Also when the 4WD button is clicked I can here a loud click but the 4WD light no longer comes on in the dash. I did have a left wheel seal done in the rear diff but i don't think it has anything to do with it.
Does anyone have any ideas?

Thanks that has helped alot. It seems there are 2 isssues -the temperature sender and the turbo
pressure switch. Need to find a couple of parts now. Low pressure and high pressure switches and a turbo pressure switch. any ideas?

Thanks that has helped alot. It seems there are 2 isssues -the temperature sender and the turbo
pressure switch. Need to find a couple of parts now. Low pressure and high pressure switches and a turbo pressure switch. any ideas?