P0262

What Does Code P0262 Mean?

DTC P0262 signifies that the Engine Control Module (ECM), also known as the Powertrain Control Module (PCM), has detected an electrical fault within the control circuit for the fuel injector on cylinder #1. Specifically, “Circuit High” indicates that the voltage observed by the ECM on the control side of the cylinder 1 injector circuit is continuously higher than the expected operating range. In a typical fuel injector circuit, the injector receives constant battery voltage on one side, while the ECM controls the injector by grounding the other side, completing the circuit and allowing fuel to spray. A “Circuit High” condition can occur if there is an open circuit in the low-side driver wire from the ECM, an internal open circuit or excessively high resistance within the injector coil itself, or a short to a voltage source (e.g., 12V power supply) on the control circuit that prevents the ECM from pulling the circuit to ground. This fault prevents the ECM from properly activating the cylinder 1 fuel injector, leading to an unmetered or completely absent fuel supply for that cylinder and consequently, a severe engine misfire.

Common Symptoms

• Malfunction Indicator Lamp (MIL) Illumination: The “Check Engine” light will be illuminated on the dashboard.
• Engine Misfire: The engine will run rough, particularly noticeable at idle, due to the lack of combustion in cylinder #1.
• Reduced Engine Power: Significant loss of power and acceleration due to one cylinder not contributing to engine output.
• Rough Idling: The engine may shake or vibrate excessively at idle speeds.
• Increased Fuel Consumption: The ECM may attempt to compensate for the misfire by richening the air-fuel mixture for other cylinders, leading to decreased fuel efficiency.
• Hesitation or Stumble: The vehicle may hesitate or stumble under acceleration.
• Abnormal Exhaust Note: A noticeable change in exhaust sound, potentially sounding “choppy” or “thumping” due to the misfire.

What Causes the Code P0262?

• Faulty Fuel Injector (Cylinder #1): An internal open circuit, short to power, or excessively high resistance within the injector’s coil preventing it from drawing current and operating correctly.
• Wiring Harness Issues:
  • Open Circuit: A break or discontinuity in the control wire from the ECM to the injector, or in the constant power supply wire to the injector.
  • Short to Voltage: The control wire for cylinder #1 is shorted to a constant voltage source (e.g., battery voltage, another power wire), preventing the ECM from effectively grounding the circuit.
  • Damaged or Corroded Connectors: Corrosion, bent pins, or loose terminals at the cylinder 1 fuel injector connector or at the ECM connector.
  • Chafed or Frayed Wiring: Physical damage to the insulation allowing the control wire to contact a voltage source.
• Faulty Engine Control Module (ECM/PCM): A rare but possible failure where the internal injector driver circuit for cylinder #1 within the ECM is damaged, causing it to fail to provide the necessary ground pulse or incorrectly sense the circuit’s state.

How to Diagnose and Troubleshoot

Diagnosis of P0262 requires a systematic approach, utilizing a digital multimeter (DMM) and an OBD-II scan tool. Safety precautions, such as disconnecting the battery before certain electrical tests, should always be observed.

1. Verify Code and Freeze Frame Data: Connect an OBD-II scan tool and confirm P0262 is present. Check for any other related codes (e.g., misfire codes, other injector circuit codes). Review freeze frame data to understand engine operating conditions (RPM, engine load, temperature, etc.) when the code was set. This provides valuable context for diagnosis.
2. Visual Inspection:
   • Visually inspect the wiring harness leading to the cylinder 1 fuel injector for any signs of physical damage, chafing, cuts, or corrosion. Pay close attention to areas where the harness passes near hot engine components or sharp edges.
   • Inspect the cylinder 1 injector electrical connector for damage, corrosion, bent pins, or loose connections. Ensure it is securely seated.
   • Examine the corresponding terminals at the ECM connector, if accessible and applicable (requires ECM connector removal, typically after battery disconnect).
3. Fuel Injector Resistance Test:
   • With the ignition OFF, disconnect the electrical connector from the cylinder 1 fuel injector.
   • Using a DMM set to ohms, measure the resistance across the two terminals of the injector itself.
   • Compare this reading to the manufacturer’s specification (typically 10-18 ohms for high-impedance injectors). An open circuit (infinite resistance or “OL” on the DMM) or a reading significantly higher than specification indicates an internal fault within the injector.
4. Power Supply and Control Circuit Voltage Test:
   • Reconnect the injector connector. Backprobe the power supply wire at the cylinder 1 injector connector (usually the wire that shows constant voltage with the ignition ON). With the ignition ON, engine OFF, set the DMM to DC volts and measure voltage between this wire and a known good chassis ground. You should read battery voltage (~12-14V). If not, diagnose the power supply circuit back to its source (fuse, relay).
   • Backprobe the control wire at the cylinder 1 injector connector. With the ignition ON, engine OFF, measure voltage between this wire and a known good chassis ground. It should typically read near battery voltage (as the ECM driver is open) or drop to 0V briefly during cranking if the ECM is attempting to pulse. A constant voltage that does not fluctuate during cranking, or stays at 0V when it should be high, could indicate a problem. An oscilloscope is ideal for observing injector pulse. A “Circuit High” typically means the control wire *stays* high (near battery voltage) when it should be pulled low by the ECM.
5. Continuity and Short to Voltage/Ground Test (Wiring Harness):
   • Crucial Step: Disconnect the battery. Disconnect both the cylinder 1 injector electrical connector and the main ECM connector.
   • Continuity: Using a DMM set to ohms, measure continuity of the control wire between the ECM connector terminal and the cylinder 1 injector connector terminal. Resistance should be very low (typically less than 0.5 ohms). Perform the same test for the power supply wire (if it terminates at the ECM).
   • Short to Ground: With the DMM on ohms, check for continuity between the control wire terminal (at either end) and a known good chassis ground. There should be no continuity (infinite resistance).
   • Short to Voltage: Check for continuity between the control wire terminal and other power wires in the harness. There should be no continuity. This helps identify internal harness shorts.
   • Load Test Wires: A DMM measures voltage and continuity but not current-carrying capacity. To thoroughly test the control and power wires, use a small incandescent test light or headlight bulb. Connect one end of the bulb to a power source (for the ground-side control wire) or ground (for the power wire), and the other to the wire in question. If the bulb illuminates brightly, the wire can carry current. If it’s dim or doesn’t light, there might be high resistance in the wire, even if continuity seems fine.
6. ECM Driver Test (Advanced/Last Resort): If all other tests confirm the injector and wiring are perfect, but the ECM is not providing the proper ground pulse, the ECM itself may be at fault. This requires specialized equipment (oscilloscope) to monitor the ECM’s output pulse or substitution with a known good ECM.

Recommended Repairs and Solutions

Based on the diagnostic findings, the appropriate repair will be:

• Replace Faulty Fuel Injector: If the resistance test of the cylinder #1 fuel injector shows an open circuit or excessively high resistance, the injector is faulty and must be replaced. Always use a high-quality OEM or equivalent replacement injector. Consider replacing the injector O-rings and seals to prevent fuel leaks.
• Repair Wiring Harness: If visual inspection or DMM tests reveal damaged, corroded, or shorted wiring, carefully repair the affected sections. Use automotive-grade soldering and heat-shrink tubing for durable repairs. Replace corroded or damaged electrical connectors entirely if necessary. Ensure all wire repairs are protected from future damage.
• Repair Corroded Terminals: If corrosion on connector pins is found, clean them thoroughly using electrical contact cleaner and a small brush. If pins are severely corroded or bent, the connector housing or individual pins may need to be replaced.
• Replace ECM/PCM: This should be considered a last resort, only after meticulously ruling out all other potential causes (injector, wiring, connectors). ECM replacement typically requires specialized programming to match the vehicle’s VIN and immobilizer system, which often necessitates dealership service or a qualified independent specialist with appropriate programming tools.

After any repair, clear the DTCs with the scan tool. Perform a test drive under various engine conditions to confirm the repair and ensure the P0262 code does not return.