KlaroFault codeP0179
MODERATEFuel Composition Sensor Circuit High Input
What this code means
Fuel Composition Sensor Circuit High Input.
P0179 is a generic code: it means the same thing on every make. P0179 belongs to family P01xx — Fuel and air metering. Its page explains how to read a code and groups all its codes by part.
Type of fault
The control unit reads a voltage on this circuit above its expected range. Usual causes: a broken wire or a poor ground, a short to a supply voltage, or the component itself. As with a low signal, check the wiring and connector before the part.
Fuel composition (ethanol) sensor
On flex-fuel vehicles, this sensor in the fuel line measures the proportion of ethanol in the fuel, from 0 to 85 % or more. The control unit adapts the quantity injected and the ignition timing, since ethanol needs more fuel for the same air.
What you notice
Hard starting, especially when cold, hesitation or lack of power after filling up with a different blend.
How to check it
Check the sensor's connector and wiring along the fuel line. Klaro shows the ethanol percentage when the car reports it: compare it with what you know you filled up with. A reading stuck at 0 or 100 % after a mixed fill-up points to the sensor or its circuit.
Watch it live in Klaro
With an OBD2 adapter plugged in, these live readings show the part at work, when your car reports them:
- Ethanol fuel percentage
- Short term fuel trim bank 1
- Long term fuel trim bank 1
What to do
Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.
Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →
How to read this code
- PPowertrain
- 0standardised code
- 1Fuel and air metering
- 79P0179
