P05C8: Economy Mode Switch Circuit Range or Performance

What it means

Same as P05C7 with the input in plausible range yet not matching expected behaviour.

At a glance

• Usually lights the check-engine light

How it works

The economy-mode switch signals the driver's ECO request to the control module. P05C8 sets when the input is present but its range or behavior does not match the expected switch operation, so the module may not respond consistently.

Common causes

Most likely first.

1. Worn or faulty switch contacts
2. Loose or corroded switch connector
3. Damaged switch wiring

Symptoms

• Check-engine light
• Economy mode may respond inconsistently to the switch
• Economy mode may be unavailable or remain selected

How to diagnose it

1. Save freeze-frame data and watch the live ECO switch status while pressing and releasing the switch several times to identify missed or inconsistent changes.
2. Inspect the switch and connector for wear, looseness, corrosion, or moisture that could cause an unstable but not fully open input.
3. Check switch output and continuity in each position against the manufacturer's specification.
4. Inspect and test the switch wiring for damage, poor pin contact, or resistance that changes as the harness is moved.
5. If the switch and wiring pass, verify the input at the control-module connector before suspecting a module fault.

Common fixes

• Clean and secure a loose or corroded switch connector.
• Repair damaged wiring or terminals in the economy-mode switch circuit.
• Replace a worn switch that produces inconsistent readings.
• Address a control-module configuration or input fault only after the switch circuit tests correctly.

Can I keep driving?

Driving is generally possible if the vehicle operates normally, since the fault concerns economy-mode selection. ECO may respond unpredictably or remain unavailable, and its effect on throttle response, shifting, or climate settings may vary.