HOW TO FIX A ‘FLOATING’ EARTH?

Q My Lada Niva failed its MOT emissions test, with the ECU reporting a lambda sensor fault. I changed the sensor, but the fault report persists, even after resetting the ECU. I probed the sensor’s connections at the ECU with a multimeter. One of the terminals should be at 0V, but it’s floating around at about 2.5V instead. The other terminal is 3V, give or take a little. Can I solve the problem by simply connecting the terminal that should be zero volts to the earth of the ECU? Harry Criddle, Ashill A Yes – we think this ought to do the trick. We suspect that a dry solder joint inside the ECU is failing to tie the lambda sensor’s circuit to earth as it’s supposed to. Making an external earth connection should serve the same function – and it’s probably a less risky solution than poking about inside the ECU with a soldering iron.