Code
P1228
OLDSMOBILE
P — Powertrain
Injector Circuit Cylinder 3 Intermittent
AI status
Completed
Completed
100%
Causes
- Damaged or corroded injector connector or wiring (open, short to power, short to ground, or intermittent contact)
- Faulty fuel injector (internal short or intermittent coil connection)
- Poor or missing power supply to the injector (blown fuse, relay, or wiring fault)
- Poor ground for the engine/ECM or ground return for the injector driver
- Faulty ECM / injector driver transistor (intermittent)
- Corroded or water-damaged harness or pin(s) at ECU or injector
Symptoms
- Intermittent or rough idle
- Occasional misfire on cylinder 3 (P0303 may accompany P1228)
- Reduced power or hesitation under load
- Check Engine Light illuminated (intermittent or stored fault)
- Possible increased fuel consumption or emissions
What to check
- Read freeze-frame and pending/final DTCs; note related codes (e.g., misfire codes)
- Visual inspection of injector 3 connector, wiring harness, and routing for chafing, heat damage, corrosion or repairs
- Back-probe injector connector with ignition ON to confirm battery feed on the power pin
- Check ground continuity from injector ground circuit to chassis/engine ground and to ECU ground
- Measure injector coil resistance and compare to factory spec or a known-good injector from another cylinder
- Wiggle test harness and connectors while monitoring scan tool or voltmeter to reproduce intermittent condition
Signal parameters
- With ignition ON (engine off): battery voltage (~12 V) present on the injector power supply pin
- Injector driver is usually low-side: when ECU fires injector the driver pulls the low-side to near 0 V (ground) producing a pulse; idle pulse width typically ~1–10 ms depending on load and rpm
- Pulse frequency varies with engine speed and fuel injection strategy; pulses become longer with greater load
- Injector coil resistance should match factory specification — compare to other cylinders; low-impedance injectors are often a few ohms to a few tens of ohms, high-impedance types higher — consult service manual
- Intermittent circuit faults often show missing pulses, irregular pulse width, or voltage spikes on an oscilloscope
Diagnostic algorithm
- Retrieve all DTCs and freeze-frame data; note whether code is current or intermittent and any accompanying misfire codes.
- Perform a visual inspection of wiring, connectors and pins for cylinder 3 injector; repair obvious damage, corrosion or loose pins.
- Verify injector power: back-probe the connector power pin with ignition ON — should read battery voltage. If missing, trace power feed (fuse, relay, harness).
- Verify ground: check continuity from injector low-side to engine ground/ECM ground. Repair if high resistance or intermittent.
- Measure injector coil resistance with the connector disconnected. Compare to factory spec or a same-engine cylinder. Replace injector if out of spec or intermittent.
- Use a noid light or oscilloscope on the injector low-side while cranking/running to confirm consistent injector pulses. Look for missing or irregular pulses or voltage spikes.
- Wiggle test wiring and connectors while monitoring signal to reproduce intermittent failure; repair or replace damaged wiring or connectors.
- If wiring and injector check good, swap cylinder 3 injector with another cylinder (if practical) and see if code follows injector (helps separate injector vs. wiring/ECM).
- If problem follows wiring or swapping doesn’t reproduce, test ECM driver output and associated circuitry per factory procedure; replace ECM only after confirming driver fault and ruling out harness/injector issues.
- Clear codes and road test to confirm repair; re-scan for recurrence.
Likely causes
- Intermittent connector/wiring fault at injector harness (most common)
- Faulty injector (stick, intermittent coil or wiring inside injector)
- Poor power or ground to injector circuit (loose fuse/relay/ground)
- ECM driver intermittently failing (least common)
Fault status
Status
P1228 — Injector Circuit Cylinder 3 Intermittent: ECU detected intermittent injector drive or irregular circuit behavior for cylinder 3. Inspect wiring, connector, injector and ECU driver.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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