P1293

What Does Code P1293 Mean?

DTC P1293 indicates that the Engine Control Module (ECM), also known as the Powertrain Control Module (PCM), has detected an open circuit condition in the “high side” electrical supply for one or more fuel injectors on Engine Bank 1. In most fuel injection systems, the high side refers to the constant battery voltage (B+) supply that is delivered to the fuel injector. The ECM/PCM then rapidly grounds the “low side” of the injector circuit to complete the circuit and activate the injector, thereby delivering fuel. When P1293 is set, it means that the ECM/PCM is commanding an injector on Bank 1 to fire, but it is not detecting the expected current flow through the circuit or senses an abnormally high voltage (near B+) on the injector driver circuit when it should be pulled low. This lack of detected current or incorrect voltage state implies a complete break or interruption in the positive voltage supply path to the injector coil(s) on Bank 1. This directly impacts the ability of the affected fuel injector(s) to operate, leading to a lack of fuel delivery to those cylinders.

Common Symptoms

• Check Engine Light (MIL) Illumination: The primary indicator that a fault has been detected.
• Engine Misfire on Bank 1: Noticeable rough running, particularly at idle, due to one or more cylinders not receiving fuel.
• Reduced Engine Performance: Loss of power and poor acceleration.
• Difficulty Starting or No-Start Condition: If multiple injectors on Bank 1 are affected, the engine may struggle to start or fail to start altogether.
• Increased Fuel Consumption: The ECM may attempt to compensate for the lean condition by over-fueling other cylinders, or simply due to inefficient combustion.
• Rough Idle or Stalling: Especially when the engine is cold or under load.
• Associated Misfire Codes: P0301, P0302, etc., specific to Bank 1 cylinders, will often accompany P1293.

What Causes the Code P1293?

• Open Circuit in Wiring Harness: A severed, chafed, or corroded wire in the high-side (B+) supply circuit leading to one or more fuel injectors on Bank 1. This is a very common culprit.
• Faulty Fuel Injector(s): An internal open circuit within the coil winding of one or more fuel injectors on Bank 1. The injector coil may have failed, leading to infinite resistance.
• Blown Fuse: The fuse supplying constant battery voltage to the fuel injectors on Bank 1 has blown, interrupting the high-side power.
• Corroded or Loose Electrical Connectors: Poor electrical contact at the main harness connector for the fuel injectors or at the individual injector connectors on Bank 1.
• Faulty Fuel Injector Relay: If the high-side power to the injectors is routed through a relay, a faulty or intermittent relay could cause an open circuit.
• Failed Fuel Injector Driver Circuit within the ECM/PCM: While less common, an internal fault within the ECM/PCM preventing it from supplying the necessary B+ voltage to the high side of the injectors or properly monitoring the circuit integrity.

How to Diagnose and Troubleshoot

Diagnosing P1293 requires a methodical approach, primarily focusing on electrical circuit integrity and component testing. A digital multimeter (DMM) and a vehicle-specific wiring diagram are indispensable tools.

1. Visual Inspection: Begin by thoroughly inspecting the wiring harness connected to all fuel injectors on Bank 1. Look for any signs of physical damage, such as fraying, chafing, cuts, or pinched wires. Check for corrosion at the main harness connectors and individual injector connectors. Ensure all connectors are securely seated.
2. Check Fuses and Relays: Consult the vehicle’s service manual or wiring diagram to locate the fuse(s) and any relevant relays responsible for supplying power to the fuel injectors. Using a DMM, check for continuity across the terminals of the fuse. If a fuse is blown, replace it. If a relay is suspected, check its operation or swap it with a known good relay of the same type (e.g., horn relay).
3. Verify High-Side Voltage at Injectors:
   • With the ignition OFF, disconnect the electrical connector from a suspected fuel injector on Bank 1.
   • Turn the ignition to the ON position (engine OFF).
   • Using a DMM set to DC Volts, measure the voltage between the “high side” (power feed) terminal of the injector harness connector and a known good chassis ground.
   • You should read approximately battery voltage (12-14V). If no voltage is present, the open circuit is upstream from this point (wiring, fuse, relay, or ECM/PCM power output).
   • Repeat this for all injectors on Bank 1 to determine if the issue is isolated to one injector or affects multiple.
4. Test Fuel Injector Resistance:
   • With the ignition OFF, disconnect the electrical connector from each fuel injector on Bank 1.
   • Using a DMM set to Ohms, measure the resistance across the two electrical terminals of the fuel injector itself.
   • Compare the reading to manufacturer specifications (typically 10-16 ohms for port fuel injectors, but can be much lower for some direct injection or diesel injectors, e.g., 0.5-2 ohms).
   • An infinite resistance (open circuit) reading indicates an internal failure of the injector coil, requiring injector replacement. A reading significantly outside the specified range also warrants replacement.
5. Continuity and Short to Ground/Power Check of Wiring: If no voltage was found at the injector connector, or if the problem appears intermittent:
   • With the ignition OFF, disconnect the main harness connector from the ECM/PCM (if safe and accessible) and all individual injector connectors on Bank 1.
   • Referencing the wiring diagram, identify the high-side power wire for the affected injector(s) at both the injector connector and the ECM/PCM connector.
   • Using a DMM, check for continuity between the identified high-side pin at the injector connector and the corresponding pin at the ECM/PCM connector. A reading near 0 ohms is expected. An open circuit (OL or infinite resistance) indicates a break in the wire.
   • Also, check for a short to ground by placing one DMM lead on the high-side wire terminal and the other on a known good chassis ground. There should be no continuity.
   • Check for a short to power by checking continuity between the high-side wire and any other power wires in the harness (ignition ON, engine OFF).
6. ECM/PCM Driver Test (Advanced): If all external wiring, fuses, relays, and injectors test good, the issue may lie within the ECM/PCM’s internal driver circuit for the high-side injector power. This usually requires specialized diagnostic equipment or professional ECM testing/replacement.

Recommended Repairs and Solutions

Once the root cause of P1293 has been identified through systematic diagnosis, the appropriate repair can be executed:

1. Repair or Replace Damaged Wiring: If the diagnostic steps indicate an open circuit or short in the wiring harness, the damaged section of wire must be repaired or replaced. Use appropriate gauge wire, solder connections, and seal with heat-shrink tubing to ensure a durable, weather-resistant repair. Ensure the repaired section is properly routed and secured to prevent future damage.
2. Replace Blown Fuse and Address Underlying Cause: If a blown fuse was discovered, replace it with a fuse of the correct amperage. It is crucial to determine why the fuse blew, as it typically indicates an overcurrent condition (e.g., a short circuit downstream). Failing to address the underlying short will result in the new fuse blowing again.
3. Replace Faulty Fuel Injector(s): If an injector coil is found to have an internal open circuit (infinite resistance), the fuel injector(s) must be replaced. When replacing injectors, it’s often advisable to replace them as a set on the affected bank, especially in higher mileage vehicles, to maintain fuel delivery balance and consistency. Always use OEM or high-quality aftermarket injectors and replace any seals or O-rings as part of the procedure.
4. Repair/Replace Corroded or Loose Connectors: If corrosion or physical damage to the electrical connectors is identified, clean the terminals thoroughly using electrical contact cleaner and a small brush. If the damage is severe, the connector body and/or terminals should be replaced. Ensure connections are tight and secure after cleaning or replacement.
5. Replace Fuel Injector Relay: If a faulty relay was identified as the cause, replace it with a new, OEM-specified relay.
6. ECM/PCM Replacement: This should be considered a last resort. Only replace the ECM/PCM if all other components and wiring have been thoroughly tested and verified as operational, and the diagnostic process definitively points to an internal ECM fault. ECM replacement often requires specialized programming or “flashing” to integrate with the vehicle, which may necessitate dealership or specialized shop assistance.

After any repair, clear the DTCs from the ECM/PCM memory using an OBD-II scanner. Perform a comprehensive test drive under varying load and speed conditions. Monitor live data, paying close attention to fuel trim values and injector pulse widths, to confirm proper system operation and ensure the P1293 code does not return.