P0681 indicates that the powertrain control module has detected an open circuit in the glow plug circuit for cylinder 11. This code applies to diesel engines equipped with individual cylinder glow plug monitoring. An open circuit prevents the glow plug from heating, which can affect cold-start performance and emissions.
The glow plug element has burned out or fractured internally, creating an open circuit.
A break in the power supply or ground wire between the glow plug controller and cylinder 11 glow plug.
High resistance or separation at the glow plug connector, harness connector, or controller connector.
Internal driver circuit failure for the cylinder 11 output within the glow plug control module.
Rare; a control module logic error or output driver failure incorrectly reporting an open circuit.
The vehicle will likely start and run once warm, but cold starts may be difficult or impossible in low temperatures. Extended driving with a misfiring cylinder can cause excess emissions and potential catalyst damage.
On many modern diesels, glow plug control is handled by a dedicated module separate from the PCM. The PCM monitors the module and sets the code when the module reports a fault.
Only the faulty glow plug is required, but many technicians recommend replacing the full set if mileage is high, since the others are likely near end of life.
No. PCM failure is a rare cause. The code is almost always due to the glow plug itself, wiring, connectors, or the dedicated glow plug control module. PCM replacement should only be considered after all other causes are ruled out.