P0671 Fault Code

Long Description

Fault code P0671 is logged when the engine control unit (ECU) has detected a malfunction with the glow plug circuit for cylinder 1.

This fault code is only found in vehicles with diesel engines as petrol engines do not rely on glow plugs.

This code is a part of a series of diagnostic codes that run from P0671 up to P0682 for engines with 12 cylinders. There is also P0670, which represents a glow plug module control circuit malfunction.

The last number in these codes indicates which cylinder’s glow plug is malfunctioning.

Unlike petrol engines, diesel engines do not rely on spark plugs for ignition. Instead, they use the heat generated from the compression cycle to cause combustion.

At low engine temperatures and cold environments, there is not enough heat generated in the beginning to ignite the air-fuel mixture. Glow plugs warm the cylinders to aid in the first few cycles when starting the engine.

Again, this fault code can only be found in diesel vehicles. Manufacturers like Audi, Volkswagen, and Ford can be some of the most commonly searched associated with this fault code.

Other Signs of This Problem

Issues involving glow plugs can cause similar symptoms to issues with spark plugs. However, these are typically relegated to the starting of the engine rather than during continuous running.

The Check Engine light is one of the most useful tools in detecting this issue while the engine is running.

Another warning light that can help pinpoint this issue is the Pre-Glow light. This will likely not turn off after turning the engine over as the glow plug never comes to the desired operational temperature.

This issue can cause a hard start with a cold engine. Additionally, the engine may not start at all.

In some instances, white smoke can be emitted from the exhaust pipe.

What Could Be The Problem?

The causes for this P0671 issue are mostly found within the cylinder 1 glow plug circuit itself.

A damaged or faulty glow plug will obviously not perform desirably.

Additionally, if the glow plug circuit is open or shorted, it can cause this code to be logged. There may also be blown fuses for this glow plug. This can be from loose or damaged wires and connections or any faulty components in the circuit.

A faulty glow plug relay may also cause this type of issue. This could come with other fault codes like P0670.

Fixes

Fixing a faulty glow plug can consist of replacing any damaged parts or addressing issues in the circuit.

One of the first things to test is the cylinder 1 glow plug. If the glow plug is not operating properly, it needs to be replaced – potentially fixing this P0671 fault code right away.

If the glow plug circuit has any damage or loose wiring, these need to be fixed. Loose or corroded connections should also be fixed. Any blown fuses need to be replaced as well.

The glow plug relay should be checked and replaced if necessary.

Seriousness

Fault code P0671 and the other glow plug codes are moderately serious issues. The engine can be damaged over time from continuously starting with a faulty glow plug.

These codes are typically not as serious as a faulty spark plug, which is a serious problem.

It is a good idea to have this issue fixed immediately if possible.