A vehicle benefits from an electric water pump in several ways. The pump is not belt-driven, which enhances performance of the vehicle, and it ­prevents the engine from being bogged down while the air conditioning is on. Another advantage of an electric water pump is the equal distribution of engine coolant throughout an engine because the pump’s propeller speed is not ­dependent on engine speed. This knowledge will help in the ­following diagnosis.

Model: 2006 BMW 525xi, 3.0L

Complaint:

The customer states the check engine light is on and the vehicle overheats.

Diagnosis:

Connected a scan tool and found codes: 2E81 – Electric Coolant Pump, Speed Deviation, Speed Outside Of The Specified Range, and 2E82 – Electric Coolant Pump Cutoff, Over Current.

Attached a pressure tester to the engine cooling system and pressurized the system to check for leaks. The engine cooling system retained the applied pressure, which indicated no leaks were present.

At idle, used a multimeter to check for the presence of voltage and ground at the engine water pump and found both were present.

Observed the engine water pump parameters on the scan tool and found the actual speed of the engine water pump impeller did not match the desired speed parameter. The results of the tests indicated the engine water pump impeller was not spinning fast enough and was faulty, which caused the vehicle to overheat.

Removed the engine coolant thermostat for inspection and found the engine coolant ­thermostat was damaged.

Solution:

Replaced the engine coolant thermostat and the engine water pump, cleared codes, performed a road test and verified the vehicle operated properly. The customer’s concern did not return.

Courtesy of Mitchell1’s SureTrack Real Fixes.