P03DA

Code

Generic P — Powertrain

Cylinder 7 Combustion Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 14 EN: 27 RU: 23

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Page language: EN

Causes

Faulty spark plug or ignition coil for cylinder 7
Fuel injector failure or poor injector spray pattern
Low compression (worn rings, damaged piston, valve issues, head gasket leak)
Intake manifold or vacuum leak affecting cylinder 7
Timing chain/belt or cam/crank correlation problem
Wiring or connector fault to injector or coil (open, short, high resistance)

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Rough idle and vibration, especially at idle or low load
Reduced engine power and acceleration
Increased fuel consumption and higher than normal exhaust emissions
Intermittent or persistent misfire on cylinder 7 (may show as cylinder-specific misfire counters)
Possible fuel trim abnormalities or occasional backfiring

What to check

Read and record DTC(s) and freeze frame data
Monitor live data: misfire counters, short/long term fuel trims, O2/HEGO sensors, RPM
Perform a visual inspection of spark plug, coil, injector, and wiring/connectors for cylinder 7
Swap ignition coil and/or injector with a known-good cylinder to see if fault follows
Measure fuel rail pressure and verify fuel delivery
Perform a relative compression/cylinder contribution test and/or wet compression test

Signal parameters

Misfire counters (cylinder 7)
Short and long term fuel trims (STFT/LTFT)
O2/HEGO sensor voltages and response
Crankshaft position sensor waveform
Camshaft position sensor waveform
Ignition coil primary/secondary waveform for cylinder 7

Diagnostic algorithm

Retrieve and record all DTCs and freeze-frame data; clear codes and attempt to re-create the issue
Visually inspect spark plug, ignition coil/coil pack, and injector for signs of damage, carbon tracking, oil fouling, or corrosion
Swap the cylinder 7 coil with another cylinder’s coil and test for code follow — if code follows coil, replace coil
Swap the cylinder 7 injector with another cylinder’s injector and test for code follow — if code follows injector, test/replace injector
Check wiring and connectors for continuity, corrosion, pin damage, and proper grounding to the injector and coil circuits
Verify fuel pressure and delivery under load; inspect fuel filter and rail for proper pressure and pulsation
Perform a relative compression or cylinder contribution test; if abnormal, perform a static compression test on cylinder 7 and compare to other cylinders
If compression is low, perform a leak-down test to determine whether leakage is past valves, rings, or head gasket
Inspect intake manifold sealing and vacuum lines; use a smoke machine or carefully apply a safe intake leak detector spray while monitoring engine speed
Check cam/crank correlation and timing marks; verify timing chain/belt condition and tension
Use an oscilloscope to compare ignition and injector waveforms between cylinder 7 and a good cylinder if available
After repairs, clear codes and perform a test drive and monitor for reappearance of the code and correct fuel trims and misfire counters

Likely causes

Worn/shorted ignition coil serving cylinder 7
Fouled, worn, or incorrectly gapped spark plug on cylinder 7
Clogged or electrically-failing fuel injector at cylinder 7
Low cylinder 7 compression from burned/warped valve, blown head gasket at that cylinder, or worn rings
Localized intake manifold gasket leak near cylinder 7 port
Damaged wiring harness/connector to injector or coil for cylinder 7

Fault status

⚠️ Status

Stored code indicating cylinder 7 combustion performance/misfire detected by the powertrain control module. Adaptive trims and misfire counters exceeded threshold for that cylinder.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-4 hours