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Home / DTC / P0279 — Cylinder injector circuit low

P0279 — Cylinder injector circuit low

Detailed page for trouble code P0279.

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Code

P0279

LAND ROVER P — Powertrain

Cylinder injector circuit low

Brand: LAND ROVER
Type: P — Powertrain
Views: UK: 3 EN: 5 RU: 3
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Page language: EN

Causes

  • Damaged or chafed injector wiring harness (short to ground)
  • Corroded or loose injector connector terminals
  • Failed fuel injector (internal short or open)
  • Poor battery/ground connections or low supply voltage
  • Blown fuse or failed power supply/relay for injectors
  • Faulty PCM / injector driver transistor

Symptoms

  • MIL (check engine light) illuminated
  • Misfire or rough running under load or at idle (misfire on specific cylinder)
  • Reduced engine power and poor drivability
  • Increased fuel consumption and higher emissions
  • Possible hard start or stumble during acceleration

What to check

  • Read freeze frame data and confirm P0279 is current or historic; note cylinder number if stored
  • Scan for related and pending DTCs (other injector or PCM codes)
  • Visual inspection of wiring and connectors at the injector and along the harness for damage, oil contamination, or corrosion
  • Check battery voltage and engine ground integrity before testing
  • Backprobe injector connector to measure supply and driver signals with key ON and while cranking / running
  • Measure injector coil resistance with multimeter and compare to specification

Signal parameters

  • Typical injector supply voltage: ~12 V (key ON) at the positive feed to each injector
  • Injector driver low circuit condition: driver output pulled toward ground when active; fault reports when driver pin voltage is lower than expected at key ON or when pulsed
  • Typical injector coil resistance (varies by engine): roughly 1–16 ohms for low-impedance injectors, 12–40 ohms for high-impedance types — consult vehicle spec
  • Injector pulse width during running: commonly 1–10 ms depending on load and RPM; oscilloscope waveform should show clean square pulses from the PCM

Diagnostic algorithm

  1. Connect a full-featured scan tool. Record freeze frame data, pending codes, and live data for injector pulse width and misfire counters. Identify the exact cylinder referenced by the code.
  2. Perform a thorough visual inspection of the injector wiring harness, connectors, and engine grounds for damage, oil contamination or corrosion.
  3. Verify battery voltage and main engine ground connections; poor supply can cause spurious low-circuit detections.
  4. With ignition OFF, disconnect the suspect injector. Measure its coil resistance with a multimeter and compare to specification. If out of range, replace the injector.
  5. With ignition ON (engine OFF), backprobe the injector positive feed to confirm 12 V supply. If absent, trace fuse/relay/power feed.
  6. Backprobe the driver pin while cranking or running: use a noid light or oscilloscope to confirm the PCM is commanding pulses. If pulses are missing or weak, inspect wiring for short to ground between the driver pin and chassis.
  7. Check continuity and resistance between the injector driver pin at the PCM connector and the injector connector. Look for short to ground or short to battery.
  8. Perform a wiggle/torque test on connectors and harness while monitoring live data for intermittent failures.
  9. Swap the suspect injector with a known-good cylinder (if accessible) to determine whether the code follows the injector or remains on the same cylinder (helps isolate injector vs wiring/PCM).
  10. If wiring and injector test good and problem follows PCM driver, consider PCM driver fault—verify with manufacturer procedures and check for relevant technical service bulletins before PCM replacement.
  11. After repair, clear codes and perform a road test or extended running to confirm the fault does not return. Document repairs.

Likely causes

  • Short to ground in the affected injector circuit
  • Faulty injector coil (low internal resistance or short)
  • Corroded/poor connector or pin making poor contact
  • Bad ground or low battery voltage preventing proper circuit operation
  • PCM driver failure (less common)

Fault status

⚠️ Status
Injector circuit low detected on the specified cylinder — the PCM reports lower-than-expected circuit voltage or driver output; MIL ON.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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