Code
P1228
CHRYSLER
P — Powertrain
Injector Circuit Cylinder 3 Intermittent
Views:
UK: 36
EN: 48
RU: 43
AI status
Completed
Completed
100%
Causes
- Broken or chafed wiring to injector #3
- Corroded or loose connector or terminal at the injector
- Failed or intermittent injector (internal short/open)
- Poor ECM/PCM driver output or intermittent internal fault
- Faulty power supply or fuse for the injector rail
- Poor ground or chassis/ECM ground connection
Symptoms
- Check Engine Light (CEL) illuminated, intermittent
- Rough idle or occasional misfire on cylinder 3
- Reduced fuel economy or hesitation under load
- Intermittent stumbling or surging that may come and go
- Possible stored misfire-related codes (e.g., P0303) in addition to P1228
What to check
- Read freeze-frame and readiness data with a capable scan tool; note conditions when DTC set
- Check for related misfire codes (P0303) and look at long/short fuel trims and misfire counts
- Visually inspect injector #3 connector and wiring for damage, corrosion, or loose pins
- Back-probe injector connector while cranking/run to verify constant 12V supply and pulsed driver signal to the injector low side
- Measure injector coil resistance and compare to factory specification
- Perform a wiggle test on harness and connector while monitoring live data or scanner for intermittent change
Signal parameters
- Injector supply voltage (Key ON): approximately battery voltage (~12 V), verify against vehicle spec
- Injector coil resistance: compare to OEM spec (typical ranges vary — confirm factory value; low-impedance injectors often 2–4 Ω, high-impedance 12–16 Ω)
- Driver output: pulsed ground switching from ECM; voltage at connector low side should toggle between ~0 V (driver ON) and ~12 V (driver OFF) when back-probed
- Pulse width: normally 1–10 ms depending on engine load and RPM (use live data or oscilloscope for comparison)
- Waveform shape: clean, repeatable square pulses; excessive ringing, long rise/fall times, missing pulses, or intermittent drops indicate wiring/driver or injector faults
Diagnostic algorithm
- Connect an advanced scan tool and record freeze-frame data and live injector status; clear codes and attempt to reproduce
- Visually inspect injector #3 connector and harness; repair any corrosion, bent pins, or obvious damage
- With ignition ON (engine OFF) back-probe the injector connector: verify constant battery voltage on the supply pin and correct ECU switching on the control pin while cranking/running
- Measure injector resistance with the connector disconnected and compare to factory spec. Replace injector if out of spec or intermittent when warmed/cooled
- Perform a wiggle/pressure test: while monitoring live data or oscilloscope, wiggle the wiring harness and connector, and if safe, run the engine to try to reproduce the fault
- Use an oscilloscope to compare injector #3 waveform with a known-good cylinder. Look for missing pulses, distorted waveform, or noise consistent with wiring damage or a failing driver
- Swap injector #3 with another cylinder’s injector (if practical). If the DTC and symptoms follow the injector, replace the injector. If the DTC remains on cylinder 3, suspect wiring or ECM
- Check continuity and resistance between injector connector and ECM pin with harness disconnected; check for short to battery/ground using an ohmmeter/diode test
- Inspect and test injector power fuse/relay and verify ECM ground points are clean and tight
- If wiring and injector check good, consult vehicle-specific service information for ECM driver tests or consider ECM replacement only after confirming driver failure with bench/controlled tests
Likely causes
- Corroded injector connector pin or water intrusion
- Damaged wiring harness near engine (heat, abrasion, rodent)
- Faulty injector that opens intermittently under load or temperature
- ECM driver stage marginal/failing
- Blown/loose fuse or poor power/ground to injector circuit
Fault status
Status
P1228 — CHRYSLER: Injector Circuit Cylinder 3 Intermittent. ECM detected an intermittent fault in the injector circuit for cylinder 3 (open/short/poor connection/driver issue).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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