P21B9

Cold Start Cylinder 4 Injection Timing

Severity

⚠️ Medium

Can you drive?

Yes, but get it checked soon

Approx. repair cost

$17–89 (est.)

Symptoms

Unstable engine operation during cold start
Increased vibration at idle
Deterioration in acceleration dynamics
Increased fuel consumption
Check Engine Light Is On

Causes

Cylinder 4 injector malfunction
Problems with the coolant temperature sensor
Fuel system contamination
Engine control unit malfunction
Problems with the wiring harness to the injector

How to Fix

Check the condition and operation of the injector of cylinder 4
Diagnose the coolant temperature sensor
Clean the fuel system
Check connections and integrity of wiring harness
Update ECU firmware if necessary

Related codes

P21B8 P21BA P0304