Code
P1225
GM
P — Powertrain
Injector Circuit Cylinder 2 Intermittent
Views:
UK: 27
EN: 46
RU: 36
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in injector circuit (pinch, chafe, corrosion)
- Loose, corroded or damaged injector connector or terminal
- Failed fuel injector (intermittent internal failure or sticking)
- Intermittent poor ground or power feed to injector
- Faulty PCM/ECM injector driver (intermittent)
- Poor battery/charging voltage or blown/intermittent fuse/relay in injector feed
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated or stored pending code
- Intermittent rough idle or misfire felt at low load
- Reduced engine performance, hesitation or stumble
- Located misfire or performance issue specifically on cylinder 2
- Poor fuel economy or drivability problems when fault is active
What to check
- Read freeze frame and scan-tool data: PID values, PCM status and occurrence history
- Visual inspection of wiring harness and injector connector at cylinder 2 for damage and corrosion
- Check battery and ignition voltage at key-on and while cranking
- Back-probe injector connector to confirm command voltage/pulse while cranking and running
- Measure injector coil resistance with multimeter and compare to spec
- Perform wiggle test of harness/connectors while monitoring for code or waveform changes
Signal parameters
- Injector coil resistance: typical few ohms to tens of ohms (compare to OEM spec)
- Injector command voltage/pulse: 0–12 V switching signal (back-probe to view)
- Injector pulse width: milliseconds (varies with load and RPM)
- Injector current draw: milliamps/amps (use current probe or lab scope)
- Battery voltage: stable 12–14.5 V during tests
- Waveform characteristics: clean switching edges, expected pulse frequency, no missing pulses
Diagnostic algorithm
- Retrieve all codes and freeze-frame data. Note whether code is confirmed or pending and any associated misfire codes (e.g., P0302).
- Perform a careful visual inspection of the cylinder 2 injector, its connector, nearby harness, and engine grounds for damage, heat, oil intrusion or corrosion.
- With key ON (engine OFF) verify injector supply voltage at the injector harness pin(s). Confirm battery voltage present on the fused feed as specified.
- Measure injector coil resistance at the connector. If open or out of spec, replace the injector.
- Back-probe the injector signal while cranking and running. Use a scan tool to command the injector ON and observe voltage/current waveform with an oscilloscope. Look for intermittent dropouts, missing pulses or abnormal amplitude.
- Perform a wiggle test of the harness and connectors while monitoring live data/waveform to reproduce the intermittent behavior.
- If safe and allowed by manufacturer, swap the injector with a known good cylinder. If code follows the injector, replace the injector. If code stays on cylinder 2, suspect wiring/PCM.
- Check continuity between the injector connector and PCM driver pin with engine off. Look for intermittent opens/shorts and insulation breakdown.
- Inspect PCM connector and grounds. Repair any damaged wiring, terminals or grounds. If wiring and injector test good and intermittent faults persist, consider PCM driver failure and consult OEM service info before replacing PCM.
- After repair, clear codes, perform a road test under various conditions and re-scan to verify the fault does not return. Document findings.
Likely causes
- Damaged/loose connector at cylinder 2 injector
- Wiring harness chafe or intermittent short to ground/12V on injector circuit
- Intermittent injector coil failure
- Corroded terminal or poor engine ground
- PCM driver fault (less common)
Fault status
Status
P1225 — Injector Circuit Cylinder 2 Intermittent. The PCM detected an intermittent problem in the cylinder 2 injector circuit. Inspect wiring/connectors, injector, power/ground and PCM driver.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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