01 Stellantis: The Birth of a New Automotive Star from FCA and… • 02 5 Things You Need to Know About Faulty Oxygen Sensors in Ca… • 03 Cruise Control: Understanding Its Functionality and Best Pr… • 04 Experts Reveal The Dangerous Truth About Cheap Brake Pads S… • 05 P0036 H02S heater control circuit (Bank 1 sensor 2) • 06 The Silent Sensor That Controls Half Your Engine Without No… • 07 Car Parts Brands that Are Trusted by Professionals • 08 Spark Plug Change: Should You Also Replace Ignition Coils T… • 09 How Mobile Mechanics Are Changing the Industry (And Making … • 10 Here's Why Your Car Feels Sluggish Even With A Full Tank Of… •

DTC codes / P06xx · Computer and output circuits / P068B

P068BECM/PCM Power Relay De-Energized Performance Too Late

P068B means the engine control module (ECM) or powertrain control module (PCM) has detected that its main power relay stayed energized longer than expected after the ignition was switched off. The computer commands the relay to de-energize, but the voltage on the relay's control circuit or the module's power feed does not drop when it should, so the module flags the timing as too late.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Often no symptoms besides the warning light, because the fault is a timing issue rather than a complete failure.
  • The battery may drain overnight or over a few days if the relay stays energized and keeps powering modules.
  • Intermittent no-start or slow crank after the vehicle sits, especially in cold weather.
  • The engine may continue running for a moment after the key is turned off, or accessories may stay powered.
  • Other unrelated codes may set in multiple modules because the power relay feeds several control units.
  • A faint click or relay chatter may be heard from the fuse box after shutdown in some cases.

Common causes, most likely first

  1. A sticking or welded power relay contact that fails to open when the coil is de-energized.
  2. A short to voltage on the relay control circuit between the ECM/PCM and the relay coil.
  3. A faulty ECM/PCM internal driver that keeps the relay coil grounded after shutdown.
  4. Corrosion or water intrusion in the relay socket or underhood fuse box causing a partial short.
  5. An aftermarket accessory wired into the relay circuit that backfeeds voltage after key-off.
  6. A poor ground on the relay coil or ECM/PCM causing erratic relay control.
  7. A relay of the wrong type or a mismatched replacement that does not release at the specified voltage.

How to diagnose and fix it

  1. Verify the battery is fully charged and inspect the power relay and its socket for corrosion, water, or loose terminals.
  2. With the key off, listen and feel the relay for a click or warmth that indicates it is still energized; substitute a known-good relay of the same part number.
  3. Measure voltage on the relay control circuit at the ECM/PCM with the key off; it should be near zero volts, and any standing voltage points to a short or backfeed.
  4. Disconnect the ECM/PCM connector and check for voltage on the control wire with the key off; voltage present confirms a wiring short rather than a module fault.
  5. Inspect for aftermarket wiring, alarm systems, or remote starters tapped into the relay circuit and remove or repair any backfeed source.
  6. If the relay and wiring test good but the ECM/PCM still holds the relay on, test the module driver circuit and replace or reprogram the ECM/PCM as needed.
  7. Clear the code and perform a key-off sleep test with an ammeter to confirm the relay releases and parasitic draw returns to normal.

What a sticking power relay really costs you

  • A relay that stays energized can keep the ECM/PCM and other modules awake, causing a parasitic draw that flattens the battery even though the engine starts fine every morning.
  • Technicians often replace the ECM/PCM first, but a shorted control wire or a backfeeding aftermarket accessory is a far more common cause of P068B than a failed module.
  • The code can set intermittently from a relay that only sticks when hot, so a cold-engine test may pass and the fault may not reproduce until the vehicle has run for a while.
  • Water intrusion into the underhood fuse box is a frequent hidden cause, especially after a car wash or heavy rain, and the relay socket may look fine until the cover is removed.
  • P068B does not always mean the relay is bad; a poor ground on the relay coil can make the ECM/PCM see the relay as still energized when it has actually released.

Can I keep driving with P068B?

You can usually drive the vehicle to a shop, but avoid leaving it parked for long periods because the relay may drain the battery. If the engine runs on after key-off or the battery goes flat overnight, stop driving and have the circuit tested promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage