Okay, here's the problem.

I have been doing some work for a friend on their 2004 Mondeo fitted with the 1.8 SCI petrol engine. The front lambda sensor had died and was showing a suitable code. Once checked with a diagnostics machine, showing the sensor to be producing incorrect values, it was changed. This was a main dealer only part due to being a 5-wire sensor and not being available on the aftermarket supply.

Now, that code is gone, but when you start the car up, the management light still comes on. When checked, fault code P0546 (Exhaust Gas Temperature Circuit High) comes up. It can be cleared and will stay off while the engine is running but will normally come back on again once the car is restarted, especially if left for a couple of minutes.

This code would mean to me that either the sensor itself is knackered or that the wiring to it has short-circuited. The problem is that I cannot find this sensor .

My initial thought was that it may be part of the lambda sensor itself, as the sensor does have what appears to be a resistor or one-way diode attached, but it is a new lambda from Ford in a sealed box. Does not mean it is not faulty, but unlikely.

Anyone got any ideas?

 

Anyone?