P21B7

Code

Generic P — Powertrain

Cold Start Cylinder 2 Injection Timing

Brand: Generic

Type: P — Powertrain

Views: UK: 32 EN: 38 RU: 31

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Faulty fuel injector (cylinder 2)
Open, shorted or intermittent injector wiring or connector
Faulty injector driver/output stage in the powertrain control module (PCM/ECM)
Low battery or poor power/ground during cranking
Incorrect fuel rail pressure or fuel delivery issues
Faulty crankshaft or camshaft position sensor (timing/sync error)

Symptoms

Rough cold idle or extended cranking time on cold start
Poor cold-engine drivability or hesitation immediately after start
Increased white/black exhaust smoke on cold start (diesel/gas variants)
Illuminated malfunction indicator lamp (MIL)
Possible single-cylinder misfire or reduced power until engine warms

What to check

Read freeze frame and stored data: engine coolant temp, intake temp, battery voltage, requested vs actual injector timing/pulse during freeze frame
Perform live data capture during cold cranking and first few seconds of cranking
Check for related codes (injector circuit, crank/cam sensors, fuel pressure)
Visually inspect wiring and connector for cylinder 2 injector for damage or corrosion
Measure injector resistance and compare to specification
Backprobe injector connector to verify pulse and voltage during cranking (use low‑voltage scope if available)

Signal parameters

Injector pulse width (ms) — commanded vs actual
Injector driver voltage at connector (V) during cranking
Battery voltage (V) during cranking
Fuel rail pressure (bar or psi)
Engine coolant temperature (°C) at time of fault
Intake air temperature (°C) at time of fault

Diagnostic algorithm

Retrieve and record freeze frame and live data. Note coolant temp and battery voltage at fault occurrence.
Clear the code and attempt to reproduce with a cold start. Capture live data during cranking and first 30 seconds of operation.
Visually inspect cylinder 2 injector connector and wiring for corrosion, loose pins, chafing or heat damage.
Measure injector coil resistance at ambient temperature and compare to spec. If out of range, replace injector.
Backprobe the injector connector while cranking. Confirm constant battery voltage on supply pin and switching pulse on the driver pin. Use an oscilloscope to verify proper waveform and timing.
If no pulse is present but driver command exists in PCM data, check continuity from PCM driver to injector connector. Repair open/shorts as found.
If pulse is present but timing/pulse width is incorrect, check crank and cam sensors for correct signals and synchronization. Repair or replace sensors as needed.
Verify fuel rail pressure and flow during cold start; correct fuel delivery problems.
Check battery condition and charging system; ensure adequate voltage during cranking.
If wiring and sensors test good but injector is confirmed functioning electrically, suspect PCM driver or software. Verify software updates with manufacturer and consider PCM repair/replacement only after confirming external circuits are good.
After repairs, clear codes and perform multiple cold-start verifications to ensure the fault does not return.

Likely causes

Corroded/loose connector at cylinder 2 injector
Wiring short to battery or ground on injector circuit
Failed injector (stuck, clogged, or electrically open)
Weak battery causing erratic driver behavior during cranking
Faulty crank or cam sensor producing a timing reference error
PCM driver transistor failure or intermittent internal fault

Fault status

⚠️ Status

PCM detected cylinder 2 cold-start injection timing outside expected parameters. Possible causes include injector failure, wiring/connector fault, sensor/timing error, low voltage during cranking, or PCM driver/software issue.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours