Faulty ignition coil with integrated driver holding the control signal high; Damaged, corroded or loose connector at the coil; Control wire shorted to a voltage supply, or chafed against another live wire; Open circuit or high resistance in the coil's earth connection, causing a false high signal reading; Water ingress or oil contamination in the coil connector or coil well; Fault in the engine control unit's output driver.

P035F

Ignition F 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
5F: FaultThe specific fault in that area

What it means

P035F means the engine control unit has detected a high voltage fault on the control signal circuit for ignition coil 'F'. The signal line between the control unit and the coil driver is reading higher than expected, which points to a short to voltage, a fault in the coil's integrated driver, or a wiring or connector problem. Which cylinder coil 'F' refers to depends on the engine and model, so confirm it from the vehicle-specific wiring information.

Symptoms

Engine warning light on
Misfire or rough running on one cylinder
Hesitation or loss of power under load
Hard starting or extended cranking
Increased fuel consumption
Flashing warning light during a severe misfire

Possible causes

Faulty ignition coil with integrated driver holding the control signal highlikely
Damaged, corroded or loose connector at the coillikely
Control wire shorted to a voltage supply, or chafed against another live wirepossible
Open circuit or high resistance in the coil's earth connection, causing a false high signal readingpossible
Water ingress or oil contamination in the coil connector or coil wellpossible
Fault in the engine control unit's output driverrare

How to diagnose

Read all stored codes and freeze frame data to see engine load, speed and temperature when the fault set, and note any misfire codes alongside.
Identify which cylinder coil 'F' is on this engine using the vehicle-specific wiring information.
Visually inspect the coil, connector and harness for heat damage, chafing, corrosion, oil or water.
Check the coil's power supply and earth connections with a multimeter against the specified values.
Swap the suspect coil with a known good one on another cylinder, clear the code and see if the fault follows the coil.
With the control unit and coil disconnected, test the control wire for short to voltage and for continuity end to end.
Using an oscilloscope or the manufacturer's procedure, check the control signal while cranking.
Only after wiring, supplies and the coil are proven good, consider a fault in the control unit, following the manufacturer's procedure.

How to fix

Replace the faulty ignition coil, and inspect the spark plugs at the same time.
Repair or replace the damaged connector terminals or connector.
Repair or replace the harness section that is shorted or damaged, using proper wiring repair methods.
Restore a good power or earth connection to the coil.
Dry out and clean the coil well and connector, and fix the source of any leak.
Replace or reprogram the engine control unit only when it is confirmed faulty, following the manufacturer's procedure.

Can I keep driving?

Medium severity

The car can be driven gently for a short time, but get it checked soon. Continued misfire can overheat and damage the catalytic converter, so avoid heavy load and stop if the warning light flashes.

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