P0383 Glow Plug/Heater Circuit B Low

P0383 points to a low condition in Glow Plug or Heater Circuit B. The controller is seeing voltage, current, or feedback lower than expected on the B circuit.

Code details

Generic OBD-II · P0

System: Ignition / Misfire
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not ignore weak batteries or voltage-drop problems when diagnosing low glow/heater circuit feedback.

Symptoms of P0383

Rough idle, shaking, or a stumble under acceleration.
A flashing check-engine light during an active misfire.
Power loss and higher fuel consumption.

Common causes of P0383

Worn spark plugs, ignition coils, or plug wires.
Fuel-delivery problems — injectors, pressure, or a lean/rich mixture.
Vacuum leaks, low compression, or a mechanical fault in that cylinder.

Useful checks before replacing parts

Check circuit B command, current draw, voltage drop, battery voltage, relay or module output, and cold-start freeze-frame data.
Inspect open glow plug elements, high-resistance connectors, blown fuse links, weak grounds, damaged harness sections, and module output faults.
Measure each load in the B circuit to find whether one plug, one heater element, or the shared feed is pulling the circuit low.

Related OBD-II codes

These nearby ignition / misfire entries can help compare wording and pin down the fault area.