code 20A503?

2018 BMW 330
98,000 MILES • 2.0L • 4 CYL • TURBO • 2WD • AUTOMATIC
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BHAMDOC1
  • MEMBER
  • 140 POSTS
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
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.
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STRAILER
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 54,174 POSTS
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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