P05C7: Economy Mode Switch Circuit Open

What it means

The economy-mode (ECO) switch input has an open circuit. The ECU cannot read whether the driver requested fuel-saving mode (changes throttle map, transmission shift points, climate strategy).

At a glance

• Usually lights the check-engine light

How it works

The economy-mode switch provides the control module with the driver's request to enable or disable ECO operation. P05C7 sets when the switch input circuit is open, so the module cannot reliably read that request.

Common causes

Most likely first.

1. Open in switch or harness
2. Pin pushed back out of connector body
3. Cracked solder joint inside the module or sensor

Symptoms

• Check-engine light
• Economy mode may not respond to the switch
• Economy mode may be unavailable or remain selected

How to diagnose it

1. Save freeze-frame data and check live switch status while pressing and releasing the economy-mode button to confirm that the module never registers a change.
2. Inspect the switch connector and harness for a disconnected plug, damaged wire, pushed-back pin, or loose terminal.
3. Check the switch operation and its circuit continuity using the wiring diagram and manufacturer's specification.
4. Test the harness between the switch and control module for an open circuit, including connector pin fit at both ends.
5. If the wiring passes, check the switch internals and module connector for an open connection before considering a module fault.

Common fixes

• Reconnect and secure a loose economy-mode switch connector.
• Repair an open or broken wire in the switch harness.
• Replace a terminal that has pushed back or cannot hold contact.
• Replace a faulty economy-mode switch if it fails its continuity test.

Can I keep driving?

The code generally affects the ECO selection rather than basic engine control, so driving is usually possible if the vehicle otherwise behaves normally. Economy mode may be unavailable or remain selected, changing throttle response, shifting, or climate operation.