Home >> BMW >> 2013 >> 535i Standard Trans >> Repair and Diagnosis >> Engine Performance >> System >> Self Diagnosis - N55 - Diagnostic Trouble Codes - DTC P1638 (BMW DTC 100001) Through DTC P10EB (BMW DTC 10BA41) >> DTC P10D4; BMW DTC 10AA21: Coolant temperature sensor, cold start: Coolant temperature too low >> Fault code