Powertrain, generic (extended)

P2DA1 Gear Shift Control Module B Supply Voltage Low

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

With shift-by-wire, the selector the driver touches is an electronic module; module B is a second one, such as a further selector station or a redundant unit. Allison's 6th-generation controls show such a pair: for module 2 they list performance, lost communication, incompatibility and invalid data (P085E, U0291, U0333, U0592), but no supply codes. P2DA1 means the 12 V feed of module B, as measured by the module or the transmission controller, is below its lower limit. No manufacturer documents P2DA1 publicly. Audi's selector lever J587 on 2019–21 A6/A7 shows how much depends on this voltage check: its evaluation logged faults and blocked range selection until new software was loaded. Battery, fuse, feed wire and ground come first.

Likely causes

Weak 12 V battery or voltage dip during cranking
Corroded ground, loose connector or high-resistance feed to module B
Fuse for module B blown or with poor contact
Voltage evaluation in module software too strict

Symptoms

  • Shifter warning in the instrument cluster
  • Range selection at the second selector ignored, vehicle stays in P
  • Fault appears together with other low-voltage codes

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–600
Time0.5–3 h

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

Parts involved

gear shift control module bwiring harness

Related codes

P2DA2P2DA3P273CP085EU0291

References: law.cornell.edu, static.nhtsa.gov, static.nhtsa.gov.