Powertrain, generic (extended)

P23D8 Cylinder 2 Fuel Heater Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P23D8 concerns how well the cylinder 2 heater works, not its wiring. According to Bosch, the Flexstart heated rail warms pure ethanol fuel at rates of as much as 30 °C a second, so a system of this kind knows roughly how quickly each heating point ought to warm up. If cylinder 2 rises clearly slower than expected, draws less current than its neighbours or never reaches its target temperature, the performance code follows. Typical reasons are an aged element, scale or varnish on the heated surface and a corroded contact that drops voltage under load. No manufacturer documents P23D8 or its thresholds publicly; CARB expects functional checks of heated fuel preparation. The driver mostly notices a rough first minute on cold ethanol. Electrical faults on this path are P23D5 to P23D7.

Likely causes

Cylinder 2 heater element with reduced output
Varnish or scale on the heated surface at cylinder 2
Corroded contact dropping voltage under heater load

Symptoms

  • Cylinder 2 runs rough for about a minute after a cold ethanol start
  • Longer cranking below freezing
  • Engine warning lamp, depending on manufacturer

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–600
Time1–3 h

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

Parts involved

fuel heater cyl 2

Related codes

P23D5P23D6P23D7P23D4P23DC

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