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U02A9 Lost Communication With Charge Air Cooler Coolant Pump A

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Water-cooled charge air coolers need an electric pump in the low-temperature circuit, normally run by the engine controller as a LIN node. U02A9 means the pump has stopped answering. GM's 2025 tables (25OBDG04B) declare it after 2.5 s without a response while the pump is enabled and the supply is 11 to 18 V, and rate it Type A. GM bulletin 23-NA-102 for 2022 to 2025 Silverado, Sierra, Tahoe, Suburban, Yukon and Escalade with the 3.0 L diesel traces it to water entering the M10 pump connector, with or without LIN code U1345. FCA's Ram 1500 case shows pushed-out terminals at connector D2476A; on 2019 Jeep Renegades without grille shutters, an exposed inline connector corrodes. Mercedes reflashes the PTCU on the GLC. CARB requires charge air cooling to be monitored. Expect a MIL and less boost.

Likely causes

Water or corrosion in the pump connector or an open inline connector
Terminals pushed out of the pump connector
Software of the LIN master controller needs an update
Charge air cooler pump electronics failed

Symptoms

  • MIL on
  • Reduced boost or hesitation at high load
  • Coolant warning or fan running at full speed on some models

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–600
Time0.3–2 h

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

Parts involved

cac coolant pump avehicle bus wiring

Related codes

U05AAP023BU0623U0284

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