Code
P1242
PORSCHE
P — Powertrain
Fuel injector, cylinder 6
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EN: 4
RU: 2
AI status
Completed
Completed
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Causes
- Failed or intermittent fuel injector (cylinder 6)
- Open, shorted or corroded wiring or connector to injector
- Poor or missing injector supply voltage or ground
- Faulty injector driver in the engine control module (ECM)
- Clogged or hydraulically damaged injector (contamination)
- Low or fluctuating fuel pressure affecting spray
Symptoms
- Check Engine Light (MIL) illuminated
- Rough idle or vibration
- Misfire on cylinder 6 (may show as reduced power)
- Increased fuel consumption or rich/lean running
- Hard starting or extended cranking
- Fuel odor or visible smoke from exhaust in severe cases
What to check
- Read freeze-frame and full DTC list with a scan tool; note related misfire or fuel system codes
- Check for active misfire counters for cylinder 6 (e.g., P0306)
- Visually inspect injector connector, wiring harness and ground for damage or corrosion
- Verify fuel rail pressure and supply stability
- Backprobe injector connector with key on and/or during cranking to verify supply voltage (battery) and switching signal
- Measure injector coil resistance and compare to factory specification
Signal parameters
- Injector coil resistance: compare to factory spec; typical ranges: low‑impedance injectors ~2–6 Ω, high‑impedance injectors ~10–18 Ω (confirm spec for vehicle)
- Injector supply voltage: approx. battery voltage (12 V) at the injector harness with key ON
- Injector control: pulsed ground from ECU; pulse width varies with load (commonly ~1–20 ms depending on operating conditions)
- When triggered: signal should switch between near battery voltage and near 0 V (pulsed), waveform should be clean without excessive noise
- Fuel rail pressure: within manufacturer spec for the engine (check service manual)
Diagnostic algorithm
- Connect scan tool, record codes and freeze-frame data; note any related misfire codes (P0306) or fuel system codes.
- Visually inspect injector 6 connector and wiring for damage, corrosion, chafing and a good ground. Repair obvious issues.
- Check fuses/relays that feed the injector rail and coils. Replace if faulty.
- With key ON, backprobe injector 6 connector: verify constant supply voltage at the power pin (battery voltage) and monitor the control pin while cranking/running for pulsed ground. If no supply, trace back to fuse/relay/wiring.
- Measure injector 6 coil resistance with a multimeter and compare to spec. If out of range, replace injector.
- Use a noid light or oscilloscope on the injector signal while cranking/running to confirm correct pulse waveform. Look for missing pulses, shorted waveform, excessive noise, or open circuit.
- If electrical checks are good, perform a fuel spray test or remove injector for bench inspection to check spray pattern and leakage. Replace or clean if mechanically faulty.
- To isolate ECM vs wiring/injector: swap injector 6 with another bank/cylinder identical injector. If code moves to the other cylinder, the injector is faulty; if it stays on cylinder 6, suspect wiring or ECM driver.
- After repairs, clear codes and road test. Re-scan to confirm the fault does not return.
- If wiring and injector check good but fault persists, consider ECM driver testing or replacement per manufacturer guidance.
Likely causes
- Faulty injector at cylinder 6
- Wiring harness damage or corroded connector at injector 6
- Low injector supply voltage (fuse/relay/ground issue)
- Injector driver fault in ECM (less common)
Fault status
Status
Fuel injector circuit or injector fault detected on cylinder 6 (manufacturer-specific).
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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