Code
P1222
BUICK
P — Powertrain
Injector Control Circuit Intermittent
AI status
Completed
Completed
100%
Causes
- Damaged or chafed injector wiring harness
- Corroded or loose injector connector pins
- Poor or intermittent ground or power feed to injector(s)
- Faulty fuel injector (internal intermittent)
- Intermittent short to battery or short to ground in the injector circuit
- Faulty or intermittent ECU/PCM injector driver
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated intermittently
- Intermittent rough idle or occasional misfire
- Occasional hesitation, stumble or reduced power under load
- Hard start or intermittent no-start conditions
- Possible increased fuel consumption or uneven running
What to check
- Retrieve freeze frame and EVAP / engine data with a scan tool; record which injector(s) flagged
- Visually inspect injector harness and connectors for damage, corrosion, or water intrusion
- Wiggle test harness and connectors while monitoring live data or scan tool for code reappearance
- Check injector connector terminals for tightness and corrosion; repair as needed
- Measure injector coil resistance with an ohmmeter and compare to specification
- Backprobe injector connector with a scope or voltmeter to observe pulse and supply voltage
Signal parameters
- Injector supply voltage: approximately battery voltage (approx. 11–14 V with key on/run)
- Injector control waveform: square pulses (ECU switches ground) — 0 V (energized) to battery voltage (off)
- Pulse width: variable with load and RPM; typical port-injector pulse widths ≈ 1–12 ms (engine/load dependent)
- Injector coil resistance: typical port injector range ~2–16 ohms (refer to vehicle service manual for exact spec)
- Intermittent faults often present as missing or irregular pulses, intermittent open/short transitions, or noisy waveforms on an oscilloscope
Diagnostic algorithm
- Read codes and freeze frame data with a capable scan tool. Note which injector circuit(s) are indicated and any accompanying codes.
- Visually inspect wiring and connectors at the indicated injector(s) and along the harness to the ECU. Repair obvious damage before further testing.
- Clear codes, perform a road or idle test while monitoring injector status and engine data. Attempt to reproduce the fault (wiggle harness, operate hood, warm engine).
- Measure injector coil resistance at the connector (unplugged) and compare to factory spec. Look for opens or highly variable resistance.
- Backprobe the injector connector and observe the control signal with a lab scope if available. Look for clean square pulses, missing pulses, or intermittent drops to 0 V.
- With key on, verify constant +12 V supply at the injector feed terminal and verify solid ground continuity to the ECU driver pin when commanded.
- Perform a wiggle test of wiring from injector to ECU while monitoring for interruptions or code drop-ins. Repair any intermittent wiring or connector faults found.
- If the injector wiring and power/ground are good but intermittent control continues, swap the suspect injector with another cylinder (if practical) to see if the code follows the injector or stays with the circuit.
- If the problem follows the injector, replace or service the injector. If the problem remains on the same circuit, further inspect/repair wiring and ECU connector. Only consider ECU/PCM replacement after all wiring, connectors, and injectors are verified good and no other circuits are affected.
- After repairs, clear codes and confirm repair by road testing and re-checking for recurrence.
Likely causes
- Broken or frayed wire at a harness bend or near cylinder head
- Corroded terminal at injector connector allowing intermittent contact
- Loose harness connector to the ECU/PCM
- Injector that internally opens intermittently when hot
- Intermittent short between adjacent circuit wires (wiring harness damage)
Fault status
Status
Intermittent injector control circuit fault detected; MIL may be illuminated. Code stored for intermittent open/short or erratic injector driver behavior.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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