Code
P0266
GWM
P — Powertrain
- T wo cylinder is incorrectly balanced
AI status
Completed
Completed
100%
Causes
- Faulty fuel injector (low flow, clogged, leaking) for cylinder 2
- Ignition fault on cylinder 2 (bad coil, spark plug, or secondary ignition wiring)
- Low compression or valve sealing problem on cylinder 2 (worn rings, burned valve, head gasket)
- Air leak (intake gasket, leaking intake manifold runner) affecting cylinder 2
- Fuel pressure or fuel rail problems reducing injector flow
- Timing issue (cam/crank misalignment) affecting cylinder filling/combustion
Symptoms
- Check Engine Light illuminated (MIL) with P0266 stored
- Rough idle or vibration, especially at idle
- Reduced engine power and poor acceleration
- Increased fuel consumption and black exhaust smoke (if rich)
- Intermittent or consistent misfire codes (often P0302)
- Failed emissions or rough running under load
What to check
- Read DTCs and freeze frame data with a scan tool; note misfire counts and conditions when code set
- Check for related codes (P0302, P0202, fuel trim codes, cam/crank correlation codes)
- Compare live data: per-cylinder contribution/balance, misfire counters, short/long term fuel trims, fuel rail pressure and MAF/MAP readings
- Perform visual inspection of ignition components and injector wiring/connectors for damage, corrosion or looseness
- Swap ignition coil and/or spark plug from cylinder 2 with another cylinder to see if fault follows
- Swap injector (or use a known-good injector) to test whether issue moves with injector
Signal parameters
- Cylinder contribution or balance percentage — should be similar across cylinders (typical deviation < ~10–15%)
- Injector pulse width (ms) — compare cylinder 2 to others at same load/RPM
- Misfire count for cylinder 2 (events/minute) or misfire counters from scanner
- Short-term and long-term fuel trim (%) — unusually high or low trims that correspond to cylinder 2 issues
- Fuel rail pressure (psi / bar) — within manufacturer spec under test conditions
- Compression pressure (psi or kPa) — compare cylinder 2 to other cylinders; significant deviation indicates mechanical issue
Diagnostic algorithm
- Retrieve all stored and pending codes and freeze frame data. Note operating conditions when P0266 set.
- Clear codes and attempt to reproduce. Monitor per-cylinder contribution, misfire counts and fuel trims in live data.
- Visually inspect ignition coil, spark plug and high-voltage wiring for cylinder 2. Replace or swap with a known-good coil/plug; if code follows, replace faulty part.
- Inspect injector connector and wiring; perform back-probing to verify injector pulse and resistance. Swap injectors between cylinders; if issue follows injector, replace injector.
- Check fuel rail pressure and perform injector flow test or observe spray pattern (use appropriate shop equipment and safety procedures).
- Perform compression and/or cylinder leak-down test on cylinder 2 and compare to other cylinders. Repair head gasket/valve or piston issues if needed.
- Check intake manifold and vacuum lines for leaks at/near cylinder 2 intake port. Repair any leaks and retest.
- Verify camshaft/crankshaft timing alignment and inspect timing chain/belt/gear condition; repair as required.
- If electrical tests show proper operation, check PCM for software updates/TSBs and verify injector driver outputs with scope; replace PCM only after ruling out other causes and per manufacturer guidance.
- After repair, clear codes, perform road/test and confirm cylinder contribution and absence of P0266 and related misfire codes.
Likely causes
- Faulty injector for cylinder 2
- Faulty ignition coil or spark plug on cylinder 2
- Low compression (mechanical) on cylinder 2
- Intake manifold gasket or vacuum leak near cylinder 2
- Wiring/connector problem to injector or coil
Fault status
Status
P0266 — Cylinder 2 Contribution/Balance. PCM detected cylinder #2 contribution out of range compared with other cylinders. Investigate fuel delivery, ignition, compression, intake leaks, timing and wiring for cylinder 2.
Repair difficulty: Medium
Diagnostic time: 1.5-4 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email