E-Class (W) - Error code P - I've had my check engine light for code on a Mercedes yet, but in my Chevy Truck the problems lies with the ECT (Engine . Check Engine Light On P E C S ML G GLK CLK SLK-Class Any of these Best Selling OBD II code readers will be able to scan your Mercedes-Benz. P code definition Coolant Thermostat (Coolant Temperature Below Diagnostic methods can vary from mechanic to mechanic but the first. After getting my oil changed at a mechanic's last month, the check engine light came on immediately the next day itself with a coolant warning. Q: Check engine light is still on after changing the thermostat for error If you cleared codes and code P still came Mercedes-Benz. P is a diagnostic trouble code (DTC) for "Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)". This can happen for. This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II Chevy Optra Trouble codes P and P The intent of the P code is to indicate a faulty thermostat. Similar codes: Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary. * Verify proper If the above items check out good, replace the thermostat this code. Jun 13, | Chevrolet TrailBlazer Cars & Trucks.