Powertrain, generic (extended)

P23CC Fuel Rail Heater Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

With P23CC the fuel rail heater control circuit sits at supply voltage when it should not, most often because the line has shorted to a battery feed or the switching element is stuck conducting. The concern is uncontrolled heating: if the element keeps running, the fuel in the rail can get hotter than intended once the engine is warm. No manufacturer documents P23CC publicly. For reference, Bosch gives a target fuel temperature window of about 70 to 125 °C for its heated Flexstart rail, depending on system pressure, and says its heating unit diagnoses the switching FETs. CARB treats heated fuel preparation as a monitored output. Hot-start problems or vapour issues are possible alongside the warning lamp. Ground shorts are P23CB, an open circuit P23CA.

Likely causes

Heater control wire shorted to a battery feed
Switching transistor in the heater unit stuck conducting
Internal fault in the fuel heater control module
Damaged terminals letting adjacent pins touch

Symptoms

  • Rail heater stays on after start
  • Hard restart when the engine is hot
  • Engine warning lamp, depending on manufacturer

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–700
Time0.5–3 h

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

Parts involved

fuel rail heater

Related codes

P23CAP23CBP23C9

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