P05CAEconomy Mode Switch Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Needs a drive cycle to confirm a fix
- 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. P05CA means the switch circuit voltage is too high – a short to positive or, with a resistor ladder, an open switch ground pulling the signal to the 5 V reference; GM's equivalent is P15A0. GM's test values: reference 4.8–5.2 V, signal at rest 0.06–0.25 V.
- What you may notice
- Eco mode not selectable
- Eco indicator not working
- Vehicle runs in normal mode
- Likely causes
- LikelySwitch ground open
- PossibleSignal line shorted to positive
- PossibleSwitch faulty
- RareModule
- 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.