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P0687: ECM/PCM power relay control: circuit high

The ECU sees too high a voltage on the control of the relay that powers it; the relay may stay switched on and drain the battery.

Code P0687 at a glance
CodeP0687
SystemEngine and transmission
GroupP06xx, Control unit and auxiliary outputs
TypeGeneric: it means the same on every make
Can you keep driving?With care

What P0687 means

The engine ECU is powered through a main relay that it switches on itself when the ignition is turned on and switches off a while after it is turned off. That relay usually feeds other engine components as well. This code means there is more voltage than expected on the relay control wire, for example from a wire touching a live feed or a relay sticking on.

Most common causes

  • Main relay with contacts stuck closed
  • Damp relay connector bridging terminals
  • Control wire touching a live feed
  • Accessory wired incorrectly into the fuse box
  • ECU fault (uncommon)

Symptoms

  • Engine will not start or is slow to start
  • Engine cuts out without warning while driving
  • Engine warning light and other lights on
  • Battery going flat while the car is parked

Can you drive with P0687?

With care You can drive if the engine is running normally, but a power fault to the ECU can leave you stranded or stop the engine on the move. Have it checked soon.

How to check it

If the battery is flat in the morning, suspect the relay: a few minutes after locking the car you should not hear any fan or pump still running. Mention this to the garage along with the code.

How to read and clear P0687 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0687 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

P0687 is a generic code, so it means the same on any make, for example on Abarth, Cupra, Hyundai, Jeep, Mini, Seat. See what Final OBD does on your car in makes and models.

What does code P0687 mean?

The engine ECU is powered through a main relay that it switches on itself when the ignition is turned on and switches off a while after it is turned off. That relay usually feeds other engine components as well. This code means there is more voltage than expected on the relay control wire, for example from a wire touching a live feed or a relay sticking on.

Can you drive with P0687?

You can drive if the engine is running normally, but a power fault to the ECU can leave you stranded or stop the engine on the move. Have it checked soon.

How do you clear P0687?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0687 comes back.