P0690: ECM/PCM Power Relay Sense Circuit High

The engine module switches its main relay coil to ground (control circuit), reads the switched voltage back on a sense line and keeps the relay on briefly after ignition off to save learned values. P0690 means the sense voltage is too high: voltage is present although the relay has been off for 2 s – a welded or sticking contact, or external voltage fed in through a short – or, on some systems, overvoltage above 18 V with the relay on. GM sets it at 4 V or more with the relay off, in 50 of 63 samples at 100 ms, lamp after two trips; GM Europe's 2.0 L turbo above 2 V with the relay off or above 18 V with it on, for 2 s, and advises fixing other short-to-voltage codes first. Modules, fans or pumps may keep running after switch-off and the battery drains overnight.

Symptoms

• Check engine light
• Module, fan or pumps keep running after ignition off
• Battery drains overnight

Most likely causes

• Relay contact sticking or welded
• Short to voltage on the sense or load line (external feed from another component)
• Control wire shorted to ground (relay permanently on)
• Overvoltage from the alternator regulator (where the 18 V limit applies)

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery and grounds
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Clear the code and see if it returns
4. If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
5. Check whether a software update is available
6. Do not replace the control module without a full diagnosis

Good to know

• Repair difficulty: easy
• It affects emissions.

What each character of P0690 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 6: Control modules and outputs
• 90: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0690?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P0690?

The most common causes are: relay contact sticking or welded; short to voltage on the sense or load line (external feed from another component); control wire shorted to ground (relay permanently on).

Related codes

• P0689ECM/PCM Power Relay Sense Circuit Low
• P0688ECM/PCM Power Relay Sense Circuit/Open
• P0686ECM/PCM Power Relay Control Circuit Low
• P068BECM/PCM Power Relay De-Energized Performance Too Late
• P0563System Voltage High

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 19OBDG03B Diagnostics
• saabwisonline.com: dtc p0685 p0689 p0690 or p1682
• gsi.ext.gm.com: 2006file1

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.