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Home / DTC / P1201 — Open injection circuit / short-circuit cylinder 1

P1201 — Open injection circuit / short-circuit cylinder 1

Detailed page for trouble code P1201.

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P1201

LAND ROVER P — Powertrain

Open injection circuit / short-circuit cylinder 1

Brand: LAND ROVER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Damaged or disconnected injector connector (cylinder 1)
  • Broken, chafed or corroded wiring in injector harness
  • Open circuit in injector coil or short to ground/12V
  • Faulty fuel injector (internal open/short)
  • Poor ground or battery supply to the injector rail or ECU
  • Faulty engine control module (driver transistor)

Symptoms

  • Malfunction indicator lamp (MIL) illuminated
  • Cylinder 1 misfire, rough idle or reduced power
  • Poor fuel economy and hesitation under load
  • Possible increased exhaust smoke or vibration during idle/cruise

What to check

  • Read freeze frame and stored codes; note engine conditions when fault set
  • Visually inspect wiring and the injector connector on cylinder 1 for corrosion, bent pins, or damage
  • Check for related codes (misfire codes, other injector circuit codes)
  • Measure injector coil resistance with ignition OFF and connector disconnected
  • Backprobe injector connector while cranking or cranking/engine running to check drive pulse and supply voltage
  • Perform continuity checks from injector connector to ECU pin to verify wiring integrity

Signal parameters

  • Expected injector supply voltage: ~11–14 V (battery voltage) at connector B+ pin with ignition ON
  • Typical injector coil resistance: low-impedance injectors ~1–4 Ω; high-impedance injectors ~10–18 Ω — check vehicle spec
  • Injector drive waveform: pulsed ground or pulsed positive depending on system; pulse width varies with load (approx 1–10 ms)
  • No injector supply short to ground or short to 12V when circuit inactive; infinite (open) or very low (shorted) continuity indicates fault
  • Driver output voltage when inactive: near battery or near 0 V depending on design; check service manual for ECU pin states

Diagnostic algorithm

  1. Connect a capable scan tool; record freeze frame, suspect cylinder and any related codes
  2. Perform a visual inspection of injector 1 connector, wiring harness and nearby components for damage or contamination
  3. With ignition OFF, disconnect injector 1 connector and measure injector coil resistance; compare to manufacturer specification (note typically 1–4 Ω low-impedance or 10–18 Ω high-impedance)
  4. Check for short to ground or short to battery: measure continuity from injector terminal to chassis ground and to battery + with connector disconnected
  5. Backprobe the injector connector with ignition ON and engine cranking (or being commanded by scan tool) to confirm the presence of supply voltage and the switching drive signal (use a scope if available to view waveform)
  6. Wiggle the wiring harness while watching live data/scan tool for intermittent changes; inspect connector pins for loose/corroded contacts
  7. If injector resistance and waveform are normal, swap injector 1 with another cylinder's injector and see if the code follows the injector (if code follows injector -> replace injector)
  8. If code stays on cylinder 1 after swap -> repair wiring or connector; perform continuity and resistance checks from injector connector to the ECM connector pins
  9. If wiring and connectors are good but driver waveform absent or abnormal, suspect ECM driver fault; confirm with workshop manual tests before ECU replacement
  10. After repairs, clear codes and road-test to confirm the fault does not return

Likely causes

  • Corroded/loose wiring connector at injector 1
  • Injector coil open or shorted
  • Wiring rubbed through and shorting to chassis or power
  • Failed injector driver inside ECM after a wiring fault or overcurrent

Fault status

⚠️ Status
Injector circuit fault detected on cylinder 1 — circuit open or shorted. ECM unable to properly drive or monitor injector 1.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours
320

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