This code indicates that the engine computer has detected an open circuit in the glow plug for cylinder 5. It is specific to diesel engines and means the electrical path to that glow plug is broken somewhere between the PCM and the plug itself.
The glow plug itself has burned out or developed an internal open circuit. This is the single most common cause of this code.
The electrical connector at the cylinder 5 glow plug can corrode, spread, or melt from heat, causing an open circuit at the connection point.
Chafed, broken, or rodent-damaged wiring in the harness leading to cylinder 5's glow plug can interrupt the circuit.
The glow plug relay or dedicated glow plug control module may have a failed output channel for cylinder 5, preventing power from reaching the plug.
Extremely rare. The engine computer could have an internal driver failure for the cylinder 5 glow plug monitoring circuit, but this is the least likely cause by a wide margin.
In warm weather you may be able to drive, but cold starts will be harder and you may see white smoke and rough idle until the engine warms. In cold weather the engine may not start at all.
Only cylinder 5 is flagged, so that is the one to address first. However, glow plugs age together, and if several are original it may be more efficient to replace the full set at the same time.
Almost never. The PCM is the least likely cause. The vast majority of P0675 cases are resolved by replacing the failed glow plug or repairing a connector or wiring issue. Replacing the PCM without ruling out all other causes first is a costly and usually ineffective approach.
It is not recommended. The remaining glow plugs work harder to compensate, and a cylinder that fires cold can wash oil from the cylinder wall, accelerating wear over time.