P0687

ECM/PCM Power Relay Control Circuit High

Q: Is it safe to drive with P0687?

Not reliably — if the main power relay circuit acts up the car can stall or fail to start. Treat it as something to fix promptly.

Q: Can I just clear P0687?

It may clear briefly, but a bad relay or control-circuit short will bring it back and can leave you stranded.

Onboard computer / power supply Generic OBD-II High

What it means

P0687 means the engine computer sees the control circuit for its own main power relay reading high — voltage present when it shouldn't be, or the relay not switching as commanded. Because this relay supplies power to the ECM/PCM and related systems, the fault can cause hard starting, stalling, or the module failing to power down correctly.

High

Can I keep driving? Risky — the main power relay feeds the engine computer, so a no-start or sudden stall is possible; get it fixed before relying on the car.

Real-world scan data

Seen in

162

scans in the past year

Found in

<0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of P0687 scans

P0685in 64.8% of scans

P0645in 40.1% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Hard starting, intermittent no-start, or unexpected stalling
Battery drain from the module or relay not powering down
Multiple unrelated codes set when the module loses power

Common causes

Most likely first

Faulty ECM/PCM power relayLikely
Short to voltage in the relay control circuitCommon
Corroded or loose connections at the relay or moduleCommon
Failed ECM/PCM driverLess often

How to diagnose & fix

Work through it in order

Scan and note whether the code is current or intermittent.
Test the power relay and its socket; swap in a known-good identical relay if available.
Check the relay control wiring for a short to battery voltage and verify grounds.
If the relay and wiring are good, the module driver may be at fault — confirm before replacing. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0687?+

Not reliably — if the main power relay circuit acts up the car can stall or fail to start. Treat it as something to fix promptly.

Can I just clear P0687?+

It may clear briefly, but a bad relay or control-circuit short will bring it back and can leave you stranded.

Read & clear P0687 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX