P0688 — ECM/PCM Power Relay Sense Circuit/Open

What Does P0688 Mean?

P0688 is a diagnostic trouble code indicating: ECM/PCM Power Relay Sense Circuit/Open. This code relates to the computer and output circuits system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of P0688

⚠️ Check Engine Light (MIL) illuminated
⚠️ Erratic ECM/PCM Power Relay Sense readings
⚠️ Related system operating intermittently
⚠️ Multiple system malfunctions

Common Causes

🔍 Wiring issue in ECM/PCM Power Relay Sense circuit (damaged, chafed, or corroded)
🔍 Faulty ECM/PCM Power Relay Sense connector or terminal
🔍 Failed ECM/PCM Power Relay Sense
🔍 ECM/PCM connection issue

Frequently Asked Questions

What does P0688 mean?

P0688 indicates: ECM/PCM Power Relay Sense Circuit/Open. The vehicle's computer has detected that the ECM/PCM Power Relay Sense is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P0688?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P0688 for extended periods may cause additional problems.

How much does it cost to fix P0688?

Repair costs for P0688 typically range from $80 to $300, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Inspect and repair ECM/PCM Power Relay Sense wiring and connectors
🔧 Replace faulty ECM/PCM Power Relay Sense

1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

P0688: ECM/PCM Power Relay Sense Circuit/Open