What it means
Same as P0689 with the sense line shorted to supply or showing higher voltage than expected. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The ECM or PCM power relay supplies switched power to the engine controller, and a separate sense circuit lets the controller monitor that relay output. P0690 sets when the sense circuit voltage is higher than expected, such as from a short to supply or a wiring fault that prevents the controller from reading the relay state correctly.
Common causes
Most likely first.
- Sense line shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
How to diagnose it
- Record freeze-frame data and scan for related power-supply or communication codes to see whether the fault coincides with a no-start, reset, or other module issue.
- Inspect the ECM/PCM power relay, fuse connections, and relay socket for corrosion, heat damage, loose terminals, or water entry.
- Trace the relay sense wire using the vehicle wiring diagram and inspect it for chafing, pinched sections, pushed-back pins, or a short to battery supply.
- With the circuit isolated as specified by the manufacturer, check whether the sense wire is unintentionally connected to a supply circuit.
- Compare relay output and sense-circuit behavior during key-on and engine operation using scan data and electrical tests specified by the manufacturer.
Common fixes
- Clean and secure corroded or loose relay-socket terminals.
- Repair the ECM/PCM relay sense wire where it is chafed or shorted to supply.
- Repair a damaged connector seal or pushed-back terminal.
- Replace the power relay if its output or switching fails the specified test.
Can I keep driving?
Driving may be unreliable because an incorrect relay sense signal can accompany controller resets, limp operation, or a no-start. If the engine stalls, warning lights multiply, or it will not restart, stop safely and arrange assistance.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.