What does it mean when a fuel injector resistance is too high?

When a fuel injector’s resistance is too high, it generally indicates a problem with the injector’s internal coil winding. The resistance of a fuel injector is determined by the number of windings and the condition of the internal wiring. Here’s what high resistance could mean:

Possible Causes of High Resistance in a Fuel Injector:

1. Internal Coil Damage or Wear – Over time, the coil inside the injector may degrade, increasing its resistance.
2. Corrosion or Oxidation – Rust or moisture inside the injector can lead to poor conductivity, raising resistance.
3. Broken or Thinned Windings – The fine copper wires inside the coil may have become damaged, reducing their ability to carry current.
4. Excessive Heat Exposure – Prolonged exposure to engine heat can cause the insulation in the injector coil to break down, increasing resistance.
5. Manufacturing Defect – In some cases, an injector may have been defective from the start.

Effects of High Resistance:

• Weak or No Injector Pulse: The injector may not open properly or may fail to operate.
• Poor Fuel Delivery: The injector might not spray the correct amount of fuel, leading to lean conditions.
• Engine Misfires or Rough Running: Uneven fuel distribution can cause hesitation, misfires, or rough idling.
• Check Engine Light (CEL): The ECU may detect injector circuit issues and trigger a diagnostic trouble code (DTC), such as P0201-P0208 (injector circuit malfunction).
• Reduced Performance and Fuel Economy: Inefficient fuel delivery can reduce power and increase fuel consumption.

How to Diagnose:

1. Measure Resistance with a Multimeter:
   • Disconnect the injector from the harness.
   • Set a digital multimeter to the ohm (Ω) setting.
   • Place the probes on the injector terminals.
   • Compare the reading with manufacturer specifications (typically 1-16 ohms, depending on the injector type).
2. Check for Voltage at the Injector Connector: Ensure the wiring is supplying the correct voltage.
3. Perform an Injector Balance Test (If Possible): This can determine if the injector is functioning properly under load.

Solutions:

• If the resistance is slightly high, cleaning the injector might help if contamination is a factor.
• If significantly high, the injector is likely failing and should be replaced.
• Check wiring and connectors for damage or corrosion, as these can contribute to circuit resistance issues.