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U069E Lost Communication With Coolant Heater A

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modeNo

Coolant heater A is an electric heater with its own control electronics that warms coolant for the cabin and, in some designs, for the traction battery – usually a high-voltage PTC unit in hybrids and EVs. The vehicle commands it over a data link, mostly LIN: DBK's 400 V heater is driven via LIN 2.0 plus a PWM input, and Webasto's 800 V range adds CAN on its larger models. U069E is stored when the commanding module stops getting answers from the heater. No manufacturer documents U069E publicly. The 2013–2014 Chevrolet Volt shows the layout with a separate coolant heater control module; GM diagnosed it with its own code B101D (PIC5943), and heat returned once the engine ran. Circuit and internal faults of this heater are P2B72–P2B75 and P2DA4–P2DA7. The driver mainly notices little or no heat in electric mode.

Likely causes

LIN or CAN line to the heater broken, shorted or connector loose

12 V supply or ground of the heater electronics missing

Control electronics inside the heater failed

Heater or master module software fault

Symptoms

Little or no cabin heat in electric mode
Engine starts more often in cold weather to supply heat (hybrids)
Slow battery warm-up or reduced charging power in frost, where the heater serves the battery

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€100–1,500

Time0.5–3 h

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

Parts involved

coolant heater avehicle bus wiring

References: static.nhtsa.gov, en.dbk-group.com, webasto.com.