Faulty economy mode switch (internal open contact, worn or contaminated); Damaged, chafed or broken wiring in the switch signal or ground circuit; Corroded, loose or pushed-out pins in the switch connector or control unit connector; Water ingress or contamination in the switch or its surrounding console area; Missing or low reference voltage or ground supply to the switch circuit; Fault within the control unit input circuit, or a software issue where a known update exists.

P05C7

Economy Mode Switch Circuit/Open.

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
C7: FaultThe specific fault in that area

What it means

P05C7 is a generic powertrain code for an open circuit in the economy mode switch circuit. The control unit expects a valid signal from the driver-selectable economy (eco) mode switch and has seen an open-circuit condition, such as a missing or out-of-range voltage. How the switch is wired, and whether it is read directly or over the network, depends on the model.

Symptoms

Economy or eco mode cannot be selected or does not stay on
Eco mode indicator light on the dash does not respond, or behaves oddly
Engine warning light on, possibly with a stored fault
Throttle response or gearbox behaviour stuck in one mode regardless of switch position
Slightly different fuel consumption or performance than usual, depending on the model

Possible causes

Faulty economy mode switch (internal open contact, worn or contaminated)likely
Damaged, chafed or broken wiring in the switch signal or ground circuitlikely
Corroded, loose or pushed-out pins in the switch connector or control unit connectorlikely
Water ingress or contamination in the switch or its surrounding console areapossible
Missing or low reference voltage or ground supply to the switch circuitpossible
Fault within the control unit input circuit, or a software issue where a known update existsrare

How to diagnose

Read all stored codes and the freeze frame data, noting whether the fault is current or intermittent, and check for related codes
Operate the economy mode switch and watch live data, if available, to see whether the switch state changes
Visually inspect the switch, its connector and the surrounding trim for damage, spilt liquid or corrosion
Check the wiring harness between the switch and control unit for chafing, stretched or broken wires, especially where it passes through flexing or trim areas
Disconnect the connector and check the terminals for tightness, corrosion and bent or pushed-out pins
Using the wiring diagram for the specific model, test the supply, signal and ground at the switch connector
Check the circuit for continuity and resistance to the control unit, and test the switch itself in both positions
Check for relevant manufacturer service bulletins or software updates for the specific model before replacing the control unit

How to fix

Replace the economy mode switch if it tests open or is faulty in either position
Repair or replace damaged wiring between the switch and the control unit
Clean, repair or replace corroded or damaged connectors and terminals
Dry out and repair any water ingress source, then replace contaminated components
Restore a missing supply or ground by repairing the cause of the fault in that circuit
Update the control unit software only if a known fault in the calibration is confirmed, or repair or replace the control unit as a last resort

Can I keep driving?

Low severity

The car can normally be driven, as this fault usually only affects the selectable economy mode. Book it in for diagnosis soon, and stop if you notice any unusual drivability or gearbox problems.

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