Code
P1364
GM
P — Powertrain
IC Cylinder 4 Not Toggling After Enable
AI status
Completed
Completed
100%
Causes
- Open or short in the injector wiring harness (cylinder 4)
- Faulty or stuck fuel injector (cylinder 4)
- Poor connector pin contact, corrosion, or bent pins at injector or PCM connector
- Blown fuse or loss of constant power feed to injectors
- Faulty PCM/engine control module driver transistor for cylinder 4
- Intermittent wiring damage (chafe, pinched, water intrusion)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Misfire on cylinder 4 or rough idle
- Reduced engine power, hesitation or poor acceleration
- Reduced fuel economy
- Possible increased exhaust emissions or visible smoke
What to check
- Read the DTCs and freeze frame with a scan tool; note related codes (misfire, injector circuit codes)
- Verify vehicle battery voltage is within specification
- Use a scan tool to command (enable) injector/cylinder 4 and watch for a change
- Use a noid light or oscilloscope at the injector connector while commanding the injector
- Measure injector coil resistance at the connector (compare to spec)
- Backprobe connector to verify constant supply voltage and switching driver (ground or high-side) when commanded
Signal parameters
- Supply: typical constant battery voltage (~12 V) present at injector feed; verify via multimeter
- Driver: PCM usually provides the switching path (low-side ground or high-side pulse) — driver should pulse when commanded
- Injector resistance: varies by engine and injector type — consult service manual; common ranges are low-impedance (≈2–5 Ω) or high-impedance (≈10–18 Ω)
- When commanded ON by the scan tool, the injector circuit should show a pulsed waveform (use an oscilloscope) or light a noid tester
- Pulse width/frequency varies with engine speed and load; a steady command from the scan tool should produce repeated pulses
Diagnostic algorithm
- Verify battery voltage and clear codes. Re-scan to confirm P1364 is current and note any related codes (P0204, P0304, etc.).
- With a scan tool, command (enable) cylinder 4/its injector while monitoring engine/data. Observe whether the injector is commanded and note PCM status.
- Attach a noid light or oscilloscope to the injector connector and command the injector. If no light/waveform, continue electrical checks.
- Inspect the injector connector and wiring for physical damage, corrosion, or poor seating. Repair any visible issues.
- Measure injector coil resistance at the connector. Compare to service specification. If out of spec, remove and bench-test or replace injector.
- Backprobe for constant supply voltage at the injector feed and check the driver side for switching when commanded. If supply is missing, trace power distribution and fuses.
- Check continuity from the injector driver pin back to the PCM pin for opens or high resistance; check for shorts to battery or ground.
- Perform an injector swap test: swap cylinder 4 injector with another cylinder. If the code/misfire follows the injector, replace the injector. If it stays on cylinder 4, suspect wiring or PCM driver.
- If wiring and injector check good, consult vehicle service literature for PCM test procedures and consider PCM driver failure or software update/TSB. Replace or reprogram PCM only after confirming driver failure per OEM procedures.
- After any repair, clear codes, perform a functional test and road test to confirm the repair and that the DTC does not return.
Likely causes
- Open/short in the cylinder 4 injector harness or a bad connector
- Failed fuel injector that does not respond to a command
- Driver transistor inside the PCM for cylinder 4 has failed
Fault status
Status
PCM commanded injector/cylinder 4 (enable) but did not detect expected toggling/pulsing on that circuit — possible open/short, bad injector, or failed PCM driver.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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