What does it mean?
Some engines use a separate cold start injection function, either an additional injector or a dedicated injection stage that adds fuel only while the engine is cold, so that starting is quick and the catalytic converter heats up rapidly. The control module switches this circuit with one of its driver outputs and monitors the electrical state of that output.
P02FB is stored when the module energises the cold start injection circuit and finds no electrical load on it: current never flows, which is exactly what an open circuit looks like. The fault is therefore electrical rather than a mixture or fuel quality problem, and it means the control path to the device is broken or the device itself has no continuity. Because the extra cold start fuel is not delivered, the engine relies entirely on its normal warm-up strategy.
Symptoms
- Long cranking and hard starting when the engine is cold
- Rough, unstable idle for the first minute or two after a cold start
- Hesitation and stumble while the engine is warming up
- MIL on with the code stored, usually logged after a cold morning start
- Higher warm-up emissions, which can cause an emissions test failure
- Completely normal running once the engine is at operating temperature, so the complaint looks intermittent
Likely causes
- Open winding in the cold start injector or valve solenoid
- Connector unlatched, or a terminal pushed out of the housing at the injector
- Broken control wire between the module and the injector, often from harness chafe or a poor previous repair
- Missing battery feed to the device: blown fuse, failed relay contact or an open supply wire
- Corroded or water damaged connector pins leaving effectively no continuity
- Failed module driver output, considered only after the wiring and the component have been proven
How to fix it
- Read the freeze frame data to confirm the fault appeared at low coolant temperature during a start event
- Inspect the injector connector and harness first: look for green corrosion, spread terminals, melted insulation and chafe points near hot or moving parts
- Measure the solenoid winding resistance at the component and compare it with specification; an infinite reading proves an open winding
- Check for battery voltage on the supply pin with the ignition on, and test the fuse and relay that feed the circuit
- Perform continuity and voltage drop tests on the control wire between the module connector and the device
- Only after the wiring and component tests come back good, check the module driver output with a test lamp or an oscilloscope
- Repair or renew what the tests condemn, clear the code and verify with an overnight cold start