Powertrain, generic (extended)

P27A3 Electric/Auxiliary Transmission Fluid Pump B Performance/Stuck Off

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P27A3 means auxiliary pump B was commanded but did not deliver: no pressure build-up, too little speed or a motor that does not respond at all. Audi documents the code. Its bulletin 34-17-25, revision 3 from 2017, covers model year 2017 A4, A5, A6 and the 2018 Q5 with the 0CJ, 0CK and 0CL seven-speed twin-clutch boxes and names P27A300, next to P27A6, P276B and U28A0, as possible companions of a rattling gear oil pump V553; a supplier assembly defect was the cause, and the pump is renewed with new bolts. For pump A the matching code is P2797, which GM's 2025 CVT tables set when both pulley pressures stay below 200 kPa during an engine auto-start. Mechanical seizure, low fluid or a weak motor are typical; stop-start goes offline.

Likely causes

Pump B mechanically defective or seized (e.g. assembly fault on Audi V553)
Fluid level too low, pump draws air
Worn pump motor or high resistance in its supply

Symptoms

  • Rattle from below the car near the gearbox
  • Stop-start disabled
  • Delayed or harsh engagement after an engine restart

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,000
Time0.5–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

aux trans pump bpump motor

Related codes

P27A2P27A6P276BP2797P277C

References: static.nhtsa.gov, gsi.ext.gm.com, law.cornell.edu.