Powertrain, generic (extended)

P27A2 Electric/Auxiliary Transmission Fluid Pump B Control Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P27A2 flags a broken control circuit between the module and auxiliary pump B, the second electric fluid pump on gearboxes that carry two. While its output is energised, the controller compares the voltage on the line with the level an intact load would pull it to; a floating line reveals the interruption. No manufacturer documents P27A2 publicly. GM's 2025 TCM tables describe the identical test for pump A as P2796: more than 200 kΩ to ground in at least 20 of 25 samples taken every 100 ms, with 9 to 15 V supply, Type B. Audi ties its pump B codes to the gear oil pump V553 of the 0CJ, 0CK and 0CL twin-clutch units. P27A4 and P27A5 are the shorted variants. Typical faults are a cracked wire, a pushed-back pin or an open motor winding; stop-start is normally withdrawn.

Likely causes

Control wire broken in the harness to pump B
Pump connector unplugged, pin pushed back or corroded
Open motor winding or internal connection in pump B

Symptoms

  • Stop-start no longer active
  • Transmission warning or MIL
  • Harsh engagement when driving off after a restart

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,000
Time0.5–3 h

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

Parts involved

aux trans pump bpump relaywiring harness

Related codes

P27A3P27A4P27A5P2796P276B

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