OBD-II Generic Error Code P0686: How to Fix It

Q: Can I drive with error code P0686?

It is not recommended. The engine may stall or fail to start, and low voltage can damage the PCM. Have it repaired immediately.

Q: Will disconnecting the battery clear code P0686?

It may temporarily clear the code, but it will return if the underlying issue (faulty relay, wiring, or PCM) is not fixed.

Q: How much does it cost to fix code P0686?

If it's a simple relay or fuse replacement, parts cost $10-$50 and labor can be DIY. If the PCM needs replacement, cost can range from $500 to $1500 including parts and reprogramming.

Q: Can a bad battery cause code P0686?

While a weak battery can cause low voltage, the P0686 code specifically points to the control circuit of the relay. A bad battery is unlikely but possible if it causes voltage drops.

Q: Where can I find the ECM/PCM relay?

Check the engine compartment fuse box or under-dash fuse panel. Consult your owner's manual for the exact location and labeling.

Abstract

Error code P0686 indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the control circuit for the main power relay. This usually means the relay or its wiring is faulty, preventing the PCM from receiving proper power. Common symptoms include a no-start condition, stalling, or the check engine light coming on.