I put my '53 plate Passat 1.9Tdi in to Nationwide Autocentres in December last for, amongst other things, to replace Coolant Temperature Sensor which they did, and guaranteed work for 12 months. A couple of weeks ago the Emmissions Control warning came on. So I checked for fault codes with my VAG-COM which came up with 17664 - Coolant Temperature Fault. So I took it back to Nationwide. Their first solution was to remove sensor and clean and replace. They did this and warning light stayed off for about 4 days. Then came back on again. Nationwide say their scanner doesn't pick up any fault codes, but I've cleared the code but the same one reappears. So Nationwide have now replaced the sensor this time, but driving it back from them today the same warning has come on yet again as soon as engine gets up to temperature. Could this be something other than the coolant temperature sensor?