Coolant Pump RES wrong behaviour
• Check the coolant pump RES fuse No1 in F564 • Check the coolant pump wiring harness for chafing or other faults • Check coolant pump RES connector M38. • Check that M38-A, M38-B and E81-B are connected. • Disconnect M38-B and measure the voltage on the cable between M38-B2 and M38-B3. If the voltage is <22V, perform a troubleshooting on the feeding cable to the pump M38 and the 24V-system. • Check that the coolant level is within the specified range. If not, refill and run the pump in deaeration mode in SDP3. • Check that the coolant has an acceptable quality (colour, viscosity, clear appearance, free from sludge and sand). If the coolant quality appears to be poor, change the coolant according to PD2255172. • Change the Coolant Pump RES (M38). • Change BMU(E81).
What you'll see
No driver-visible symptom recorded.
System reaction
• Amber warning lamp "Hybrid System Fault" is shown in ICL • No or reduced cooling of the battery
Diagnostic depth
• Coolant Pump RES speed don’t match with the requested speed
• Bad connection • Internal error • Pump impeller stuck