Open circuit or high resistance in the wiring between the control unit and the cold start injector; Corroded, loose or damaged connector at the cold start injector; Failed cold start injector with an open internal coil; Blown fuse or faulty relay in the injector power supply, where fitted; Damaged pin or terminal at the control unit connector; Internal driver fault in the engine control unit.

P02FB

Cold Start Fuel Injection Control Circuit/Open.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
2: AreaFuel and air metering (injector circuit)
FB: FaultThe specific fault in that area

What it means

P02FB means the engine control unit has detected an open circuit in the control circuit for the cold start fuel injection system. This is normally a dedicated cold start injector or a cold start injection function, depending on the engine. The control unit monitors the circuit when it commands the injector and sees no current flow or an out-of-range voltage, which points to a break in the wiring, a poor connection or a failed injector coil.

Symptoms

Engine warning light on
Long cranking or hard starting when the engine is cold
Rough idle or hesitation for the first minute after a cold start
Black smoke or a fuel smell on cold starts if the fault causes over-fuelling
Poor cold-weather starting that improves once the engine is warm

Possible causes

Open circuit or high resistance in the wiring between the control unit and the cold start injectorlikely
Corroded, loose or damaged connector at the cold start injectorlikely
Failed cold start injector with an open internal coillikely
Blown fuse or faulty relay in the injector power supply, where fittedpossible
Damaged pin or terminal at the control unit connectorrare
Internal driver fault in the engine control unitrare

How to diagnose

Read and record the freeze frame data and any other stored codes, noting the coolant and intake air temperature when the fault set. Check for related injector or supply voltage codes.
Find out from the manufacturer's data how this engine implements cold start injection. It may be a separate injector or a function of the main injectors, and the checks depend on this.
Visually inspect the injector, its connector and the wiring harness for chafing, heat damage, corrosion, water ingress or pushed-back pins.
Check the relevant fuse and relay, and confirm there is a supply voltage at the injector connector with the ignition on.
Measure the injector coil resistance and compare it with the manufacturer's specification. An open reading means the injector has failed.
With the connector unplugged, check the control wire for continuity to the control unit and for shorts to earth or supply.
Use a suitable test lamp or oscilloscope to confirm the control unit is pulsing the circuit during a cold start request, if the conditions allow.
If wiring and injector are good, inspect the control unit connector pins and only then consider a control unit fault.

How to fix

Repair or replace the damaged wiring section, using proper soldered or crimped and sealed joints.
Clean, repair or replace the corroded or damaged connector and terminals.
Replace the cold start injector if its coil is open or outside specification.
Replace the blown fuse or faulty relay after finding out why it failed.
Repair the control unit connector pins, or replace or repair the control unit only after all other causes are excluded and the manufacturer's procedure is followed.

Can I keep driving?

Medium severity

The car can usually be driven once it has started, but cold starting may be poor and could leave you stranded in cold weather. Get it checked soon, and avoid repeated long cranking attempts.

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