Volvo Repair: 855 t5 Eating Coolant Temp Sensors, coolant temp, water coolant

Question
Hi James
At wits end with my car, I've had it to dealers twice in the last few weeks with a failed water coolant sensor, first time it went got all kinds of strange problems revving engine lights fading ABS light on so took it to volvo who read code 123 replaced the temp sensor and all was well for 2 weeks, dreaded lambda light came on (no symptoms car was running perfectly) so I pulled over switched off the engine cooling fan remained on car would not start again, the AA arrived 90 minutes later and the car started no problems, temp gauge went to 3 o'clock cooling fan ran constantly, drove to volvo no problems whatsoever other than cooling fan running constantly, volvo said "ok maybe a faulty sensor" they fitted a new thermostat and a new sensor and sent me on my way all was well for a month then exact same thing happened light on cooling fan stayed on, so I bought a sensor myself and fitted it, it ran for 15 mins before wrecking the new sensor, checked all the wiring apart from a tiny nic in the wire at the connection all seemed ok, tested the voltage coming from ECU and it reads around 5 volts, Volvo now want to fit a new ECU although they admit that this might not be the problem, anybody got any ideas, or should I go for ECU replacement.............please help I love my T5 dearly

Answer
The ECU could or could not fix it.  It would be hard to say.  If it was warranty then it wouldn't be an issue but it's way too old for that.  Its too hard to say what could be eating sensors like that.  What condition is the coolant in?  I don't really think that could do it but I'm almost at a loss without being able to investigate myself with the volvo system tester and looking for any unusual readings in the computer.  Ask the dealer if they called Tech hotline; they sometimes have some more helpful information.  The engineers there will be able to come up with a solution.  I may say to just go ahead with the ecu BUT before you agree to let them do the repair ask them what your liability for the repair is if it doesn't fix the problem.  I know I wouldn't want to get my car back basically the same way I got it and them asking 1000 for it.  I'll check for sevice bulletins on the car and get back to you with any other information if I find something new. (note: tech line is available ONLY to new car dealers).  Hope that helps.

James