P21A1

Code

LAND ROVER P — Powertrain

Cylinder 6 - air fuel ratio imbalance

Brand: LAND ROVER

Type: P — Powertrain

Views: UK: 28 EN: 157 RU: 31

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Page language: EN

Causes

Faulty or leaking fuel injector for cylinder 6
Clogged or restricted injector or fuel delivery to that cylinder
Ignition problem (weak spark or open coil/plug) causing incomplete combustion
Intake manifold leak, gasket leak or port leak at cylinder 6
Low compression or mechanical fault on cylinder 6 (valve, piston rings)
Wiring or connector fault to injector, ignition coil or cylinder sensor

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Rough idle, surging or vibration at idle
Poor throttle response, hesitation or reduced engine power
Lower fuel economy or visible smoke on exhaust (depending on rich/lean condition)
Misfire counters or cylinder contribution test shows cylinder 6 underperforming

What to check

Read all stored codes and freeze-frame data; note related codes (misfires, fuel system, O2/AFR sensors)
Capture live data: short-term and long-term fuel trims, O2/AFR sensor(s) and cylinder contribution
Inspect wiring and connectors for injector and ignition coil at cylinder 6 for damage, corrosion or disconnection
Measure fuel rail pressure and compare to specification (static and under load)
Check injector resistance and compare to specification; perform injector activation test
Scope injector and ignition coil waveforms while engine is running (or during cranking)

Signal parameters

Short-term fuel trim (STFT) for affected bank
Long-term fuel trim (LTFT) for affected bank
O2/AFR sensor voltage or lambda value(s) for bank(s) and downstream sensors
Injector pulse width and injector current for cylinder 6
Cylinder contribution or misfire counter for cylinder 6
Fuel rail static and dynamic pressure (psi/bar)

Diagnostic algorithm

Retrieve the code, freeze-frame and any accompanying DTCs. Note operating conditions when fault set.
Visually inspect wiring, connectors and harness around injector and coil for cylinder 6. Repair any damage or corrosion.
Compare fuel trims and O2/AFR readings between cylinders and banks to confirm the imbalance is localized to cylinder 6.
Check fuel rail pressure and filter condition. If fuel pressure is out of spec, address fuel supply before cylinder-level tests.
Test the injector: measure resistance, perform an activation flow test or use a noid light/scope to confirm pulse and current. Swap injector with another cylinder to see if fault follows injector.
Inspect and/or swap ignition coil and spark plug with another cylinder to rule out ignition issues.
Perform a compression and/or leak-down test on cylinder 6 to identify mechanical issues.
Perform a smoke test of the intake for leaks at the intake runner or gasket near cylinder 6 and inspect the PCV system.
If available, use an oscilloscope to compare injector and coil waveforms to a known-good cylinder while running under similar load.
After repairs or component swaps, clear codes and perform a road test or drive cycle to confirm the condition does not return.
If testing points to sensor or ECU issues, verify sensor operation and update ECU software/ECU replacement only after eliminating mechanical and wiring causes.

Likely causes

Injector sticking, leaking or electrically open on cylinder 6
Connector corrosion or broken injector/coil wiring harness conductors
Local intake manifold gasket leak at cylinder 6 or throttle body/PCV leak affecting that port
Weak spark from worn spark plug or faulty coil causing apparent AFR imbalance
Degraded compression on cylinder 6 causing poor cylinder contribution to AFR

Fault status

⚠️ Status

Cylinder 6 air–fuel ratio imbalance detected — the powertrain control module has identified a persistent AFR deviation attributed to cylinder 6.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5 - 3 hours (varies with needed tests and parts swaps)

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P21A1 — Cylinder 6 - air fuel ratio imbalance