Code
P1225
PORSCHE
P — Powertrain
Fuel injector, cylinder 1
Views:
UK: 5
EN: 11
RU: 5
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring to injector #1
- Poor or corroded connector at injector #1
- Failed fuel injector (electrical or mechanical)
- Faulty injector driver in the engine control module (ECM)
- Blown fuse or faulty fuel pump/injector power relay affecting injector supply
- Contaminated or clogged injector preventing normal flow
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Rough idle or vibration due to a misfire on cylinder 1
- Loss of power or hesitation under load
- Reduced fuel economy and increased emissions
- Hard start or extended cranking time
- Possible fuel smell from leaking injector
What to check
- Read ECU stored codes and freeze-frame/data snapshot
- Check for related codes (misfire, fuel pressure, communication faults)
- Visually inspect injector #1 connector and wiring for damage, corrosion or pin push-out
- Measure fuel injector resistance and compare to factory specification
- Back-probe injector connector while cranking/running to verify command voltage and pulse
- Use a noid light or oscilloscope on injector connector to confirm injector drive pulse presence and shape
Signal parameters
- Injector coil resistance (Ω) — compare to factory spec (typical values vary by system)
- Injector supply voltage — approx. battery voltage (~12 V) at connector (when key on)
- Injector command signal: pulse width (ms) — varies with load/idle, commonly ~1–10 ms
- Injector duty cycle (%) under high load — should remain below 100%
- Injector waveform shape (oscilloscope) — look for clean on/off transitions and expected peak-and-hold behavior for low-impedance injectors
Diagnostic algorithm
- Verify code and gather freeze-frame information; note engine conditions when fault occurred.
- Inspect harness and connector at cylinder 1 injector for damage, corrosion, bent pins or poor seating. Repair connectors as needed.
- Check related fuses and injector power/relay circuits; confirm injector supply voltage with key on.
- Measure injector coil resistance and compare to specification. Replace injector if resistance is open or well out of spec.
- Back-probe the injector connector while cranking/running: verify constant supply voltage and that the ECU is commanding the injector (pulse present). Use a noid light or oscilloscope for confirmation.
- If injector is commanded but not operating electrically, swap the suspect injector with a known-good injector from another cylinder and see if the fault/misfire follows the injector.
- If fault follows the harness/ECU pin after swapping, perform continuity and short-to-ground/short-to-battery checks on the injector wiring to the ECU; repair any wiring faults.
- If wiring checks good and the injector behaves correctly when driven directly, consider ECU injector-driver failure; confirm with manufacturer procedures before ECU replacement.
- Check fuel rail pressure and perform an injector flow test to rule out mechanical clogging or leakage.
- Clear codes and perform a road test to verify repair; monitor for return of the code.
Likely causes
- Broken/shorted wire between ECU and cylinder 1 injector
- Corroded/inward-pushed terminal in the injector connector
- Injector stuck open or leaking on cylinder 1
- Injector solenoid coil open or shorted (out-of-spec resistance)
- ECU output transistor for injector #1 failed
Fault status
Status
Fuel injector circuit/fault detected for cylinder 1 — injector not responding or out of specification.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 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