On all four wheels their will be a sensor and 'sensing' plate. First step is to clean these all up with a parts cleaner, and try again. If one of the sensors cant pick up a signal from the plate, then this will cause a fault. If no luck, inspect the wiring to and from the sensors, for obvious damage/short circuits. Hopefully this would have sorted it, otherwise their could be a faulty abs sensor. As for tyre pressures, i am not sure how the system works. What type of warning? If it is like some aftermarket systems, then maybe a battery has gone in flat on one of the wheel sensors
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On all four wheels their will be a sensor and 'sensing' plate. First step is to clean these all up with a parts cleaner, and try again. If one of the sensors cant pick up a signal from the plate, then this will cause a fault. If no luck, inspect the wiring to and from the sensors, for obvious damage/short circuits. Hopefully this would have sorted it, otherwise their could be a faulty abs sensor. As for tyre pressures, i am not sure how the system works. What type of warning? If it is like some aftermarket systems, then maybe a battery has gone in flat on one of the wheel sensors