Faulty or sticking economy mode switch; Wiring fault in the switch circuit, such as a short to voltage or chafed insulation; Corroded, loose or damaged connector at the switch or control unit; Open circuit in the signal or ground wire causing the signal to read high; Moisture or spilled liquid inside the switch or switch panel; Fault in the control unit or in a module that reads the switch, depending on the model.

P05CA

Economy Mode Switch Circuit High.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
5: AreaVehicle speed, idle control and auxiliary inputs
CA: FaultThe specific fault in that area

What it means

P05CA is a generic code meaning the control unit has detected a high voltage in the economy mode switch circuit. The switch lets the driver select a more fuel-efficient drive mode. The code sets when the signal voltage stays above the expected range, which may point to a short to voltage, an open circuit that lets the signal float high, or a faulty switch.

Symptoms

Economy mode cannot be switched on or off
Economy or eco indicator light stays off, stays on or behaves erratically
Malfunction indicator lamp or a warning light may be on
Throttle response or performance feels different from normal, or the car is stuck in one drive mode
Fuel economy may change if the mode is stuck

Possible causes

Faulty or sticking economy mode switchlikely
Wiring fault in the switch circuit, such as a short to voltage or chafed insulationlikely
Corroded, loose or damaged connector at the switch or control unitpossible
Open circuit in the signal or ground wire causing the signal to read highpossible
Moisture or spilled liquid inside the switch or switch panelpossible
Fault in the control unit or in a module that reads the switch, depending on the modelrare

How to diagnose

Read all stored codes and freeze frame data, and note whether other drive mode or switch circuit codes are present
Check whether the code is current or history by clearing it and seeing if it returns, after recording the data
Visually inspect the switch, its surround and the wiring for damage, water ingress or previous repairs
Disconnect and inspect the switch connector and the control unit connector for corrosion, bent pins and poor terminal tension
Using live data, watch the switch state while pressing it, and check it changes cleanly
Measure the supply, signal and ground at the switch against the manufacturer wiring diagram, as the circuit layout varies by model
Test the signal wire for a short to voltage and for continuity back to the control unit, with the connectors disconnected
Test the switch itself for correct resistance or switching action as per the manufacturer data

How to fix

Replace the economy mode switch if it is faulty or sticking
Repair or replace damaged wiring that is shorted to voltage or open circuit
Clean or replace corroded or damaged connectors and terminals
Dry out and treat the cause of any water ingress, and replace affected components
Repair or replace the control unit only after the wiring and switch are proven good, following the manufacturer procedure

Can I keep driving?

Low severity

The car can normally be driven as the fault mainly affects the drive mode selection. Book it in for diagnosis soon, particularly if other warning lights are on or the car drives abnormally.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.