Code
P1222
OLDSMOBILE
P — Powertrain
Injector Control Circuit Intermittent
AI status
Completed
Completed
100%
Causes
- Damaged or frayed injector wiring harness
- Poor/loose/chafed connector pins, corrosion or contaminant in injector connectors
- Intermittent open or short to power, ground, or other circuits
- Faulty fuel injector (internal short/open or intermittent coil)
- Faulty engine control module (ECM) / intermittent driver transistor
- Poor engine or battery ground(s) affecting injector circuit
Symptoms
- Check Engine Light (CEL) — P1222 stored (may be intermittent)
- Intermittent misfire or stumbling under load
- Rough idle or hesitation during acceleration
- Occasional hard starting or reduced engine power
- No consistent drivability symptoms when fault is intermittent
What to check
- Retrieve freeze-frame data and all stored codes; note which cylinder(s) or bank are indicated
- Visually inspect injector connectors, wiring harness, and nearby components for damage, corrosion, melted insulation or pinch points
- Wiggle-test harness and connectors while monitoring for code set or misfire to reproduce intermittent behavior
- Verify battery voltage and main power feeds to injector circuits with ignition ON and cranking
- Backprobe injector connector and check for reference power/voltage and switching signal using a multimeter or noid light
- Use an oscilloscope (preferred) to capture primary injector waveform while cranking/idle to detect intermittent drops or noise
Signal parameters
- Injector coil resistance: typically in the range of ~2–16 Ω depending on injector design — consult vehicle service manual for exact spec
- Primary (control) circuit: switched to ground by PCM; backprobe should show battery voltage at one side and pulsed ground on control lead when cranking/running
- Pulse pattern: timed pulses (square wave) matching injector pulse width; duty cycle/pulse width varies with load and RPM
- Using a lab scope: expect clean, repeatable square pulses without intermittent dropouts or noise; intermittent open/shorts show missing pulses, spiking, or collapsed waveform
- Noid light: should flash when cranking/running — an intermittent/no flash indicates control circuit fault
Diagnostic algorithm
- Read and record all DTCs and freeze-frame data; clear codes and attempt to reproduce P1222. Note conditions when it sets (temp, rpm, load).
- Visually inspect injector connectors, wiring harness, nearby fasteners, and ground straps for damage, corrosion, or heat. Repair obvious issues.
- Perform wiggle test: with scan tool monitoring the Injector command (or misfire/engine rpm) and/or noid light attached, move harness and connectors to try to reproduce fault.
- Verify power and ground: with key ON, check battery voltage at the injector power feed and continuity of ground to chassis/engine. Repair loose grounds or power feeds.
- Measure injector coil resistance (engine off) and compare to spec. If out of range or intermittent reading, suspect injector. Replace or bench-test injector.
- Backprobe control wire while cranking/running: use a noid light or multimeter to confirm pulse presence. If pulses intermittent or absent, use an oscilloscope to capture waveform for missed pulses, noise or shorting.
- If waveform shows intermittent/no drive, inspect continuity between injector connector pin and PCM pin. Repair any open/short/poor splice. Check connector pin fit and corrosion.
- Swap suspect injector with another cylinder (if practical) and see if code or misfire follows the injector. If it follows, replace injector.
- If wiring and injectors are good but intermittent commands persist, test/replace PCM or driver transistor only after confirming harness and injector integrity and checking for ECM-related TSBs.
- After repairs, clear codes and road/test under same conditions that produced the fault to confirm repair. Re-scan for pending codes.
Likely causes
- Corroded or loose injector connector pins
- Broken/shorted wiring between injector and PCM due to vibration or rubbing
- Intermittent injector coil failure
- Weak or intermittent ground at engine/chassis ground strap
- Faulty PCM driver for specific injector circuit
Fault status
Status
Injector control circuit intermittent — intermittent/open/short detected in fuel injector primary/control circuit. Check injector connectors, wiring, ground, and ECM driver.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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