Faulty or sticking cylinder 9 fuel injector; Wiring harness damage or poor electrical connection at the cylinder 9 injector; Clogged or restricted fuel passage within the cylinder 9 injector or rail; Failed injection timing control solenoid or actuator (on systems with variable timing); Engine control module software calibration issue or internal fault; Low fuel pressure affecting injection timing consistency; Mechanical wear in the high-pressure fuel pump or timing components

DTC codes / P01xx · Fuel and air metering / P01DB

P01DBCylinder 9 Injection Timing Performance - Over Retarded

Q: What does code P01DB mean?

Cylinder 9 Injection Timing Performance - Over Retarded. P01DB indicates that the engine control module has detected the fuel injection timing for cylinder 9 is more retarded than the commanded value during operation. The computer compares the actual injection event timing to the desired timing and sets this code when the deviation exceeds a calibrated threshold, typically due to a mechanical or electrical fault in the cylinder 9 injector circuit or fuel system.

P01DB indicates that the engine control module has detected the fuel injection timing for cylinder 9 is more retarded than the commanded value during operation. The computer compares the actual injection event timing to the desired timing and sets this code when the deviation exceeds a calibrated threshold, typically due to a mechanical or electrical fault in the cylinder 9 injector circuit or fuel system.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaFuel and air metering

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or misfire sensation, especially noticeable at low engine speeds
Reduced engine power or sluggish acceleration under load
Increased fuel consumption due to inefficient combustion
Occasional engine stumble or hesitation during acceleration
Exhaust odor or slight black smoke if injection timing is severely retarded

Common causes, most likely first

Faulty or sticking cylinder 9 fuel injector
Wiring harness damage or poor electrical connection at the cylinder 9 injector
Clogged or restricted fuel passage within the cylinder 9 injector or rail
Failed injection timing control solenoid or actuator (on systems with variable timing)
Engine control module software calibration issue or internal fault
Low fuel pressure affecting injection timing consistency
Mechanical wear in the high-pressure fuel pump or timing components

How to diagnose and fix it

Connect a scan tool and verify P01DB is current, then check for related codes and freeze-frame data
Inspect the cylinder 9 injector electrical connector and wiring for corrosion, chafing, or loose pins
Measure injector resistance and compare to manufacturer specification to rule out an open or shorted coil
Perform a fuel pressure test and check for restrictions in the fuel supply to the cylinder 9 injector
Use a lab scope to compare injection timing signals between cylinder 9 and a known-good cylinder
If electrical and fuel checks pass, remove and bench-test or replace the cylinder 9 injector
After repair, clear codes and perform a relearn or adaptation procedure if required, then verify the code does not return

Cylinder 9 injection timing pitfalls

A stuck or slow-responding injector often causes this code without setting a misfire code, so technicians who only look for misfires may miss the root cause.
Wiring harness issues near the cylinder 9 injector are common on engines with high underhood temperatures, and a visual inspection alone may not reveal internal wire breaks.
On engines with variable injection timing, a failing timing control solenoid can affect multiple cylinders, but cylinder 9 may be the first to set a code due to its position in the firing order.
Fuel pressure that is marginally low can cause retarded injection timing on one cylinder without affecting others enough to set a fuel trim code.
Replacing the injector without checking the electrical circuit or fuel pressure often leads to a repeat failure and unnecessary expense.

Can I keep driving with P01DB?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing because prolonged driving with retarded injection timing can damage the catalytic converter and increase fuel dilution in the oil.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.