P0178 - Fuel Composition Sensor Circuit Low Input

The fuel composition sensor signal is lower than expected.

Code Overview

The fuel composition sensor signal is lower than expected.

Common Causes

• Sensor fault
• Short to ground
• Wiring damage

Diagnostic Steps

1. Inspect the harness for chafing
2. Check signal voltage and reference voltage
3. Confirm connector fit and terminal condition

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

Browse the closest code-family pages when the same fault pattern often shows up nearby.

Next Steps

Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.