Faulty or sticking fuel injector for cylinder 1; Wiring harness damage or poor electrical connection at the cylinder 1 injector; Contaminated or degraded engine oil affecting variable valve timing (VVT) operation; Failed VVT solenoid or phaser for the bank containing cylinder 1; Camshaft or crankshaft position sensor signal interference or failure; ECM software calibration issue or internal fault

DTC codes / P01xx · Fuel and air metering / P01CB

P01CBCylinder 1 Injection Timing Performance - Over Retarded

Q: What does code P01CB mean?

Cylinder 1 Injection Timing Performance - Over Retarded. P01CB indicates that the engine control module (ECM) has detected the fuel injection timing for cylinder 1 is more retarded than the commanded value during operation. The ECM compares the actual injection event timing, often via crankshaft speed fluctuations or injector current feedback, against the desired timing and sets this code when the deviation exceeds a calibrated threshold.

P01CB indicates that the engine control module (ECM) has detected the fuel injection timing for cylinder 1 is more retarded than the commanded value during operation. The ECM compares the actual injection event timing, often via crankshaft speed fluctuations or injector current feedback, against the desired timing and sets this code when the deviation exceeds a calibrated threshold.

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 when the engine is cold
Reduced engine power or sluggish acceleration
Increased fuel consumption due to inefficient combustion
Occasional hard starting or extended crank time
Exhaust smoke or unusual odor from unburned fuel

Common causes, most likely first

Faulty or sticking fuel injector for cylinder 1
Wiring harness damage or poor electrical connection at the cylinder 1 injector
Contaminated or degraded engine oil affecting variable valve timing (VVT) operation
Failed VVT solenoid or phaser for the bank containing cylinder 1
Camshaft or crankshaft position sensor signal interference or failure
ECM software calibration issue or internal fault

How to diagnose and fix it

Verify battery voltage and inspect the engine oil level and condition, as low or dirty oil can affect VVT and injection timing
Perform a visual inspection of the cylinder 1 injector connector and wiring for chafing, corrosion, or loose pins
Use a scan tool to check for related camshaft and crankshaft position sensor codes and freeze-frame data
Test the cylinder 1 injector resistance and compare it to the manufacturer's specification
Check the VVT solenoid operation and oil control valve for the bank containing cylinder 1
Perform a compression test and cylinder leak-down test to rule out mechanical issues
If all electrical and mechanical checks pass, reprogram the ECM with the latest calibration or replace it if faulty

Don't overlook oil quality and VVT

A clogged oil control valve or sludged oil passages can retard injection timing without setting a VVT-specific code, so oil maintenance history is critical.
The code may be set by a marginal camshaft position sensor that still produces a signal but with incorrect timing, which many technicians miss.
Injector balance rates or cylinder contribution tests can reveal a weak injector even when resistance checks pass.
On some engines, a stretched timing chain can cause this code by altering the relationship between the cam and crank sensors.
After repairs, the ECM may require a relearn procedure or a drive cycle to clear the code and verify the fix.

Can I keep driving with P01CB?

You can drive the vehicle short distances to a repair shop, but avoid heavy acceleration or towing. Prolonged driving with this code may cause catalytic converter damage or worsen engine performance.

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.