Cylinder 9 Injector Circuit Low
The P0285 code indicates that the Engine Control Module (ECM) has detected a low voltage or resistance in the electrical circuit for the fuel injector on cylinder 9. This typically means the injector circuit is shorted to ground, has an open circuit, or the injector itself has low internal resistance. The ECM monitors the injector driver circuit and sets this code when the voltage is below the expected threshold during the injector activation.
01. Most Common Causes
- Faulty fuel injector on cylinder 9 (shorted or low resistance)
- Open or shorted wiring in the injector circuit
- Damaged connector at the injector or ECM
- Faulty ECM (rare)
02. Symptoms You Will Notice
- Engine misfire on cylinder 9
- Rough idle or hesitation
- Check Engine Light illuminated
- Possible fuel smell or decreased fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the injector connector and wiring for damage, corrosion, or loose connections.
Step 3: Measure resistance of cylinder 9 injector; compare to specification (typically 12-16 ohms).
Step 4: Check for voltage at the injector connector with key on; should see battery voltage on one pin.
Step 5: Use a noid light to test injector pulse while cranking; if no flash, check wiring and ECM output.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause engine misfire, reduced performance, and potential damage to the catalytic converter. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost typically ranges from $150 to $400, depending on whether the injector needs replacement ($100-$250) or if wiring repairs are needed. Labor adds $50-$150.