Powertrain, generic (extended)

P2798 Electric/Auxiliary Transmission Fluid Pump A Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2798 reports the control circuit of auxiliary pump A pulled low, which in practice means a short to ground. In GM's 2025 TCM tables the controller registers less than 0.5 Ω between the signal and controller ground in 20 of 25 samples at a 100 ms rate, with battery voltage between 9 and 15 V; it is a Type B fault with the MIL after two trips. On the Chevrolet Bolt EV (2021–2023) and Bolt EUV (2022–2023), GM bulletin 21-NA-148 groups P2798 with P2797 and P0C2D: the 12-volt fluid pump on the left of the drive unit came from a batch with faulty soldering, and the pump is replaced as a unit because it cannot be repaired. Drivers get a message that propulsion power has been reduced. P2796 covers an open line, P2799 a short to voltage.

Likely causes

Control wire chafed through to ground
Internal defect in the pump electronics (e.g. faulty solder joints, Bolt EV/EUV)
Moisture or corrosion bridging pins in the connector
Faulty control output in the module

Symptoms

  • Reduced propulsion power message on electric vehicles
  • Service vehicle soon lamp or MIL
  • Stop-start disabled on combustion models

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–1,200
Time0.5–3 h

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

Parts involved

aux trans pump awiring harness

Related codes

P2796P2799P2797P0C2DP27A4

References: gsi.ext.gm.com, static.nhtsa.gov.