Leaking or stuck-open fuel injector on cylinder 7; Injector wiring or connector fault on cylinder 7 (high resistance, damaged pins, poor earth or supply); Restricted airflow to cylinder 7, such as inlet runner or port deposits, or an intake fault affecting that cylinder only; Mechanical fault on cylinder 7, such as a valve not sealing, low compression or a worn valve train; Ignition fault on cylinder 7 causing poor combustion that the ECU reads as a rich condition; Fuel pressure too high or a faulty pressure regulator affecting the whole bank, with cylinder 7 the first to reach its limit; Faulty oxygen sensor or exhaust sensor giving a false rich reading for the bank.

P02B3

Cylinder 7 - Fuel Trim at Min Limit.

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)
B3: FaultThe specific fault in that area

What it means

P02B3 means the engine control unit has found that the fuel trim correction for cylinder 7 has reached its minimum limit, so it is taking away as much fuel as it is allowed to. The ECU sees that cylinder 7 is running richer than the others, or that the cylinder is behaving as if it has too much fuel or too little air, and cannot lean it off any further. This code only applies to engines with at least seven cylinders and individual cylinder fuel trim.

Symptoms

Rough idle or a misfire-like shake
Engine management light on
Smell of fuel from the exhaust
Black smoke or sooty exhaust
Poor fuel economy
Hesitation or uneven running under load

Possible causes

Leaking or stuck-open fuel injector on cylinder 7likely
Injector wiring or connector fault on cylinder 7 (high resistance, damaged pins, poor earth or supply)possible
Restricted airflow to cylinder 7, such as inlet runner or port deposits, or an intake fault affecting that cylinder onlypossible
Mechanical fault on cylinder 7, such as a valve not sealing, low compression or a worn valve trainpossible
Ignition fault on cylinder 7 causing poor combustion that the ECU reads as a rich conditionpossible
Fuel pressure too high or a faulty pressure regulator affecting the whole bank, with cylinder 7 the first to reach its limitrare
Faulty oxygen sensor or exhaust sensor giving a false rich reading for the bankrare

How to diagnose

Read all stored and pending codes and the freeze frame data; note whether other cylinder trim or misfire codes are present
Check live fuel trim data, comparing cylinder 7 with the other cylinders and bank trims at idle and under light load
Inspect the cylinder 7 injector connector and wiring for damage, corrosion, water ingress and bent or loose pins
Inspect the cylinder 7 ignition coil and spark plug for fouling, wet fuel or wear; compare with a neighbouring cylinder
Test the cylinder 7 injector electrically (resistance and driving signal) and check for leakage or poor spray pattern, following the procedure for the engine
Check fuel pressure and fuel pressure regulation against the manufacturer's specification for the engine
Check for restricted intake runners or ports, and carry out a compression or leak-down test on cylinder 7 if the fault persists
Check the relevant oxygen or air-fuel ratio sensor readings for plausibility

How to fix

Replace the leaking or faulty cylinder 7 injector
Repair or replace damaged injector wiring, connectors or terminals
Replace a worn spark plug or faulty ignition coil on cylinder 7
Clean or repair restricted intake runners or ports where deposits or a blockage are found
Repair the internal engine fault found on cylinder 7, such as valve sealing or compression loss
Correct fuel pressure faults by repairing or replacing the regulator or related fuel system components

Can I keep driving?

Medium severity

The car can usually be driven for a short time to reach a workshop, but a persistently rich cylinder can wash oil from the bore, foul plugs and overload the catalytic converter. Get it diagnosed soon, and stop driving if it runs very roughly, smells strongly of fuel or the engine light flashes.

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