P05C8Economy Mode Switch Circuit Range/Performance
- Generic OBD-II code · Powertrain
- How the car detects it
- The economy mode switch selects a fuel-saving mode (flatter pedal map, earlier upshifts, sometimes reduced A/C). It is usually a resistor ladder with 5 V reference read by the engine module; CARB names a driver-selectable eco mode as an off-cycle technology whose use must be counted. GM reports the same switch with its own codes P159F/P15A0, type B with warning lamp after two trips; P05C7–P05CA appear in no manufacturer document available to us. P05C8 means the signal is in range but implausible – between valid ladder steps or permanently pressed; GM accepts a press only for 0.094–1.5 s.
- What you may notice
- Eco mode switching unintentionally or not at all
- Indicator flickering or off
- Usually no check engine light
- Likely causes
- LikelySwitch stuck (permanently pressed)
- PossibleContact resistance or corrosion shifting the voltage step
- RareSoftware
- RareModule input
- Repair
- Easy · Often possible to do yourself.Typical cost: €30 – €200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.