P0273 - Cylinder 5 Injector Circuit Low
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0273 is a generic diagnostic trouble code (DTC) indicating that the Engine Control Module (ECM) has detected a lower than expected voltage in the control circuit for the fuel injector of cylinder 5. The ECM monitors the current and voltage drop across each injector. When the injector is not being pulsed, the ECM expects to see battery voltage on the signal wire. If the ECM perceives a low voltage condition when the circuit should be high, it triggers P0273. This is typically caused by a short to ground in the wiring harness or a low internal resistance (short) within the injector solenoid itself, potentially leading to misfires and fuel trim imbalances.
Possible Causes
Short to ground in the wiring harness for injector 5
Internal short or low resistance in fuel injector 5
Corroded or loose electrical connector at the injector
Internal ECM/PCM hardware failure
Symptoms
Recommended Solution
- Visual Inspection: Check the wiring and connector for injector 5 for signs of chafing, melted insulation, or corrosion.
- Resistance Test (Ohm): Disconnect the injector connector and measure the resistance across the injector pins. Normal values are typically 11–18 Ohms (check factory specs). If resistance is near 0 Ohms, the injector is shorted.
- Circuit Testing: Use a Noid light to check for injector pulses from the ECM. Verify 12V power supply with the ignition on.
- Component Replacement: Replace the injector if it fails resistance tests. Repair harness if a short to ground is found. Clear codes and perform a road test.
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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