P0178: Fuel Composition Sensor Circuit Low Input

What does P0178 mean?

P0178 is a diagnostic trouble code indicating "Fuel Composition Sensor Circuit Low Input". The ECU is detecting a voltage reading that is below the expected range in the fuel metering circuit. This typically points to a wiring short, a faulty sensor, or a grounding issue.

Symptoms you may notice

• Check engine light (MIL) illuminated on dashboard
• Poor fuel economy
• Rough idle
• Hesitation during acceleration
• Intermittent warning lights

Common causes

• Damaged or corroded wiring harness
• Loose or disconnected electrical connector
• Failed fuel metering sensor or actuator
• Blown fuse in the related circuit
• Poor ground connection

What should you do?

Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.