P0264

What Does Code P0264 Mean?

The diagnostic trouble code P0264, “Cylinder 2 Injector Circuit Low”, indicates that the Engine Control Module (ECM), also known as the Powertrain Control Module (PCM), has detected an electrical anomaly within the fuel injector circuit for cylinder number 2. Specifically, the ECM monitors the voltage drop and current flow across the injector’s driver circuit when it commands the injector to open. A “circuit low” condition typically signifies that the ECM is seeing an unexpectedly low current flow or an open circuit, implying that the circuit is not drawing the expected amount of power or is experiencing excessive resistance. This can result from an open in the injector coil, high resistance in the wiring, a poor connection, or an issue with the ECM’s internal driver for that specific injector. The ECM performs this monitoring to ensure proper fuel delivery, and when an inconsistency is detected on Cylinder 2’s circuit, it registers P0264, illuminates the Check Engine Light (CEL), and may initiate a failsafe mode to prevent potential engine damage or excessive emissions. This fault directly impacts the fuel injection subsystem for Cylinder 2, compromising precise fuel delivery.

Common Symptoms

• Check Engine Light (CEL) Illumination: The primary and most immediate indicator.
• Engine Misfire (Cylinder 2): Often accompanied by P0302 (Cylinder 2 Misfire Detected). This is a direct consequence of improper fuel delivery.
• Rough Engine Idle: Due to imbalanced combustion from the misfiring cylinder.
• Reduced Engine Performance: Noticeable loss of power, hesitation, and poor acceleration.
• Increased Fuel Consumption: The ECM may attempt to compensate by enriching other cylinders, or unburnt fuel from the non-firing cylinder may pass through the exhaust.
• Unusual Engine Noises: Such as ticking from the engine compartment (if the injector is mechanically stuck or partially operating).
• Fuel Odor from Exhaust: If the injector is not firing, raw fuel may be pushed into the exhaust, leading to a strong fuel smell.

What Causes the Code P0264?

• Faulty Fuel Injector (Cylinder 2): An internal open circuit within the injector’s solenoid coil, or excessively high internal resistance, preventing proper current flow when commanded by the ECM.
• Wiring Harness Issues:
  • Open Circuit: A broken or severed wire in either the power supply (B+) wire or the control wire from the ECM to the Cylinder 2 injector.
  • High Resistance: Corroded or damaged wiring, or a loose/frayed connection, increasing electrical resistance beyond acceptable limits.
  • Damaged Connector Pins: Corroded, bent, or spread pins within the injector electrical connector or the ECM connector affecting Cylinder 2.
• Faulty Engine Control Module (ECM/PCM): A damaged or inoperative internal injector driver circuit for Cylinder 2. This is less common but can occur and should be considered after ruling out external components.

How to Diagnose and Troubleshoot

Diagnosing P0264 requires a systematic approach, utilizing a digital multimeter (DMM) and an OBD-II scanner:

1. Verify the Code and Clear Misfire Data: Connect an OBD-II scanner and confirm P0264 is the primary code. Check for any related misfire codes (e.g., P0302). Review live data, paying close attention to fuel trims and misfire counters for Cylinder 2. Clear any adaptive fuel trims and misfire data after initial scan.
2. Visual Inspection of Wiring and Connectors:
   • Carefully inspect the wiring harness for Cylinder 2’s fuel injector. Look for signs of chafing, cuts, pinch points, or heat damage from the injector connector back towards the main harness and ECM.
   • Inspect the injector’s electrical connector for corrosion, loose terminals, or bent/pushed-out pins. Ensure it’s securely seated.
3. Fuel Injector Resistance Test (DMM):
   • Turn the ignition OFF.
   • Disconnect the electrical connector from the Cylinder 2 fuel injector.
   • Set your DMM to measure ohms (Ω).
   • Measure the resistance across the two terminals of the injector itself. Compare this reading to the manufacturer’s specifications (typically 10-18 ohms, but consult service manual). An “OL” (open line) reading or significantly higher resistance indicates a faulty injector.
   • For comparison, measure the resistance of an injector on a known good cylinder and verify consistency.
4. Power Supply Voltage Test (DMM):
   • With the injector connector still disconnected, turn the ignition to ON (Key On, Engine Off – KOEO).
   • Set your DMM to measure DC volts.
   • Connect the negative lead of the DMM to a known good chassis ground.
   • Probe one terminal of the Cylinder 2 injector wiring harness connector. One terminal should show battery voltage (approximately 12V). This is the power supply side.
   • If no battery voltage is present, trace the power supply wire back through the vehicle’s electrical system, checking for open circuits or blown fuses relevant to the injector circuit.
5. Injector Control Circuit Test (Noid Light / DMM – Advanced):
   • With the injector connector still disconnected, connect an appropriate noid light into the Cylinder 2 injector harness connector.
   • Attempt to crank the engine (or run it briefly if safe). The noid light should flash, indicating the ECM is sending a control signal (ground pulse) to the injector.
   • If the noid light does not flash, the issue lies in the control wire from the ECM or the ECM’s internal driver for Cylinder 2.
   • Advanced DMM Continuity Test (ECM disconnected): If the noid light test fails, turn ignition OFF. Disconnect the ECM connector. Using your DMM in continuity mode, test the continuity of the control wire from the injector harness connector to its corresponding pin at the ECM connector. Test for open circuits or shorts to ground/voltage on this wire.
6. Injector Swap Test (if applicable and accessible): If you suspect the injector but want to confirm before replacing, carefully swap the Cylinder 2 injector with an injector from a known good cylinder (e.g., Cylinder 1). Clear codes, restart the engine, and see if the fault code shifts to the new cylinder (e.g., P0261 for Cylinder 1). This confirms the injector itself is faulty.

Recommended Repairs and Solutions

Based on the diagnostic findings, the following repairs and solutions are recommended:

• Replace Faulty Fuel Injector (Cylinder 2): If the resistance test of the injector itself failed, or if the injector swap test confirmed the fault moved with the injector, replace the Cylinder 2 fuel injector. Always use a high-quality, OEM-specified replacement to ensure proper spray pattern and flow rate. Remember to replace any associated O-rings and seals during installation.
• Repair or Replace Wiring Harness: If visual inspection or DMM continuity tests revealed an open circuit, high resistance, or short in the wiring to the Cylinder 2 injector, repair or replace the damaged section of the harness. Use appropriate gauge wire, solder connections, and protect with heat-shrink tubing for durability. If the damage is extensive, a section of the harness or the entire engine harness may need replacement.
• Clean Connectors: If corrosion was found on the injector or ECM connectors, use a suitable electrical contact cleaner and a small brush to remove corrosion. Apply a thin layer of dielectric grease to prevent future corrosion and ensure good electrical contact.
• ECM/PCM Replacement: Only consider replacing the ECM after exhaustively ruling out all other possibilities, including the injector itself and all wiring to and from the ECM. ECM replacement is costly and often requires programming or “flashing” to the vehicle’s specific VIN and options, which should be performed by a qualified technician or dealership.
• Post-Repair Procedures: After any repair, clear all diagnostic trouble codes using the OBD-II scanner. Perform a drive cycle that includes various engine speeds and loads to allow the ECM to re-learn fuel trims and confirm the fix. Monitor live data for misfire counts on Cylinder 2 and fuel trims to ensure proper operation.