Hello everyone. This is my first post, so forgive me for missing information and like to ask. I have a problem with my girlfriend’s Opel Adam. It’s the 1.4 with 87 hp (Z16XE). In addition to the code 89 displayed in the on-board computer, the radiator fan runs at the highest level as soon as the engine is switched on or the code appears in the AI until the ignition is switched off. I have already checked a lot and am now at a loss. I have used a simple ELM327. I have already checked the following. I have carried out the measurements both on the sensor on the thermostat and on the cooler. – Visual inspection of the plugs, pins and wires of sensors and ECU for damage or similar – Resistance of the coolant sensors at ambient temperature (25°C) and operating temperature (80 °C). For comparison I have taken a new sensor. 55591401 from Febi/Bilstein) -> Plausible values and small deviations – New Senso – Power supply sensors ~4,99 V – Short circuit between signal circuit and power supply B+ checked. – Through measurement between sensor plug and ECU (both lines <2,0 Ohm) - Through measurement between both lines to exclude short circuit. I changed the coolant about 3 months ago and aired the system. Therefore, I exclude air inclusions. However, I would have this often you The cooling water is not completely clean. But therefore the error m.M.n. should not come. Please correct me if I am wrong. Does the sensor on the engine give the signal to the AI and the one on the cooler is responsible for the engine control or what is it like? Maybe I should focus on the sensor on the cooler again.. I really don't know any more. I don't think the ECU is defective, but I don't know what else to check. Therefore my Anmeld Thank you for your help.