Powertrain, generic (extended)

P23DA Cylinder 3 Fuel Heater Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P23DA tells that the control side of the cylinder 3 heater sits at a high level. The likely pictures are a control wire touching a positive feed, so voltage stays on the line when the channel is off, or an output stage that has failed conducting, so heater 3 runs without command. The second case is the costly one: Bosch rates one heat circuit at about 260 W at 12 V, which is more than 20 A, and a heater that keeps running after the engine is shut off will drain the battery within a few hours. A heater 3 that is still warm long after switch-off, or an unexplained flat battery, fits this code. No manufacturer publishes P23DA; CARB requires the circuit to be monitored. Low fault: P23DB, open: P23D9, cylinder 2 counterpart: P23D6.

Likely causes

Channel 3 output stage failed conducting
Cylinder 3 control wire shorted to a positive feed
Heater supply relay contacts welded

Symptoms

  • Flat battery after the car has stood for some hours
  • Heater at cylinder 3 warm long after switch-off
  • Engine warning lamp, depending on manufacturer

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€60–500
Time0.5–2.5 h

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

Parts involved

fuel heater cyl 3

Related codes

P23D9P23DBP23DCP23D6P23DE

References: bosch-mobility.com, law.cornell.edu.