Powertrain, generic (extended)

P23D3 Cylinder 1 Fuel Heater Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P23D3 reports that the control circuit of the cylinder 1 fuel heater is pulled toward ground. It follows the high code P23D2 in the numbering, not the other way round. A ground short on a heater path rated at a few hundred watts lets far too much current flow, so the heater unit or a fuse cuts the channel and cylinder 1 starts with cold fuel while the other heaters still work. Bosch states that its Flexstart unit detects shorts on its four heat circuits individually and reports them to the engine module. No manufacturer documents P23D3 publicly. CARB demands circuit checks on heated fuel preparation outputs. Expect a one-cylinder stumble on cold ethanol starts and possibly a blown fuse. Open circuit is P23D1, the other cylinders follow from P23D7.

Likely causes

Cylinder 1 heater wire chafed to ground on the intake or engine
Heater at cylinder 1 shorted to its housing
Fuel or water in the cylinder 1 heater connector
Shorted channel 1 output in the heater unit

Symptoms

  • Single-cylinder misfire on cold ethanol starts
  • Blown fuse in the fuel heater circuit
  • 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 1

Related codes

P23D1P23D2P23D4P23D7

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