code 20A503?

2018 BMW 330
98,000 MILES • 2.0L • 4 CYL • TURBO • 2WD • AUTOMATIC
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BHAMDOC1
Car was leaking coolant from the oil filter housing. Had that changed and since then the drivetrain message keeps appearing. Drives fine with no issues or check engine light. Removed the harness from the turbo coolant auxiliary pump and it shows open circuit. Checked and found 1 ground then with ignition on another ground, bt not sure if I can get a 5v from the 3rd wire while the car is running and cold or I have to wait till after the car is warm and then shut it off and see if I get a signal , because all this pump does is cool turbo after shut off.
Code 20a503
Apr 21, 2026 at 11:10 AM
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STRAILER
  • ✓ASE Certified Mechanic
  • 54,487 POSTS
  • ASE Certified Mechanic
Yep, this codes happens when the auxiliary water pump is bad, I would replace it and then clear the codes. Please let us know what happens.
Apr 22, 2026 at 7:43 AM
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