Wiring fault on the coil D control circuit, such as a short to voltage or chafed insulation; Corroded, loose or damaged connector at the coil D plug or the control unit; Faulty ignition coil D with an internal driver or igniter fault holding the signal high; Open circuit or high resistance in the signal wire or ground, causing the signal to float high; Poor power or earth supply to the coil, caused by a bad earth point or blown fuse; Fault inside the engine control unit driver stage.

P031F

Ignition D Control Signal Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
3: AreaIgnition system or misfire
1F: FaultThe specific fault in that area

What it means

P031F means the engine control unit has detected the control signal circuit for ignition coil D is reading high when it should not be. The control unit monitors the signal it sends to the coil driver or integrated igniter and has seen a voltage stuck high or out of range. Which cylinder coil D serves depends on the engine and firing layout, so check the manufacturer's data for the specific model.

Symptoms

Engine management light on
Misfire or rough running, especially at idle or under load
Hesitation or loss of power
Hard starting or occasional no-start
Poor fuel economy
Possible flashing warning light if a misfire is severe

Possible causes

Wiring fault on the coil D control circuit, such as a short to voltage or chafed insulationlikely
Corroded, loose or damaged connector at the coil D plug or the control unitlikely
Faulty ignition coil D with an internal driver or igniter fault holding the signal highlikely
Open circuit or high resistance in the signal wire or ground, causing the signal to float highpossible
Poor power or earth supply to the coil, caused by a bad earth point or blown fusepossible
Fault inside the engine control unit driver stagerare

How to diagnose

Read all stored and pending codes and note the freeze frame data (engine speed, load, temperature) to see when the fault set.
Check for related misfire or other ignition coil codes, as these show whether the problem is isolated to coil D.
Visually inspect the coil D connector, wiring and nearby loom for heat damage, chafing, oil contamination or corrosion.
Check which cylinder coil D serves using the manufacturer's data, then swap the coil with a known good one and see if the fault follows the coil.
Check the coil's power supply and earth with a multimeter, including the relevant fuse.
Test the control signal wire for continuity, and for short to voltage or ground between the coil connector and the control unit, with the battery disconnected as needed.
Use an oscilloscope or the manufacturer's procedure to check the signal pattern at the coil while cranking or running.
Only after wiring, power, earth and coil are proven good, consider testing or replacing the control unit.

How to fix

Repair or replace damaged wiring on the coil D control circuit.
Clean, repair or replace the corroded or damaged connector terminals.
Replace the faulty ignition coil D, and check the spark plug in that cylinder at the same time.
Restore the power supply or earth connection, including replacing a blown fuse once the cause is found.
Repair or replace the engine control unit only if all other causes are ruled out and the fault is confirmed.

Can I keep driving?

Medium severity

Short, gentle journeys are possible, but a misfire can overheat and damage the catalytic converter, so get it fixed soon. If the warning light flashes or the engine runs very roughly, stop driving and have it checked.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.