P1228 — Injector Circuit Cylinder 3 Intermittent

Diagnostic algorithm

1. Retrieve all active and pending codes and freeze-frame data. Clear codes and perform a test drive to attempt to reproduce the fault.
2. Inspect visually: engine off, examine cylinder 3 injector connector and harness for corrosion, bent pins, damaged insulation, crushed wires, or evidence of water ingress.
3. Wiggle test: back-probe the injector connector and monitor live data or misfire counters while wiggling the harness to try to reproduce the intermittent condition.
4. Resistance test: disconnect harness and measure injector coil resistance at cylinder 3. Compare to OEM spec. If out of spec or open intermittently, replace injector.
5. Noid/scope test: with engine cranking or running, confirm injector pulse using a noid light or preferably an oscilloscope. Note pulse presence, waveform shape, and voltage levels. Intermittent or missing pulses indicate wiring/ECM driver issue.
6. Voltage/continuity: check battery feed to injector and continuity from injector control pin to ECM driver pin. Check for short to power or ground. Repair damaged wiring or restore continuity as needed.
7. Swap test: if safe and practical, swap the suspected injector with another cylinder and clear codes. If the code follows the injector, replace the injector. If the code stays on cylinder 3, focus on harness/PCM side.
8. Connector/terminal repair: repair or replace corroded connectors, replace damaged pins, use proper terminal crimps and dielectric grease as appropriate.
9. PCM verification: if wiring and injector check good and fault persists, test PCM driver outputs per factory procedure or consult dealer — intermittent driver faults are less common but possible. Consider ECM replacement only after exhaustive wiring and injector verification and after checking for applicable TSBs or software updates.
10. After repair, clear codes and perform full drive cycle to verify the intermittent fault does not return.