P0670 Code: Glow Plug Control Module Circuit / Open

Is your vehicle’s check engine light on? Plug a scan tool into your vehicle to check if it has any trouble codes. If the P0670 code has been triggered, read this article to learn about the code’s definition, common causes, and common symptoms.

What Does the P0670 Code Mean?

The P0670 code is defined as Glow Plug Control Module Circuit/Open. The P0670 triggers when the powertrain control module (PCM) detects a problem with the glow plug control module or its circuit.

Some diesel-powered vehicles have glow plugs. When the key is turned, the glow plug control module or PCM will turn on the glow plugs for a set amount of time. The amount of time the glow plugs are activated is dependent on the temperature detected by the sensors.

Problems with the glow plugs tend to result in starting problems since the combustion chambers of diesel engines need to be pre-heated by the glow plugs before startup. Otherwise, diesel won’t combust properly, which can result in various engine-related symptoms.

Note: The definition of the P0670 code can be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P0670 Code?

The following problems can trigger the P0670 code:

• Failed glow plug control module
• PCM failure
• Failed glow plug
• Circuit problems, such as a damaged wire or poor connection

What are the Common Symptoms of the P0670 Code?

The P0670 code can cause your vehicle to show the following symptoms:

• Difficulty starting or refusal to start in cold weather
• Engine knock while the engine is cold
• Lack of power while the engine is cold
• White smoke from the exhaust after the engine start
• Illuminated check engine light

How to Diagnose the P0670 Code

A faulty glow plug module or glow plug wiring harnesses are some of the common causes of the P0670 code. However, you should never assume that your vehicle has these issues without verifying with a proper diagnosis. However, a proper diagnosis might be difficult because the part might not be easily accessible. Additionally, you might need special tools or knowledge in order to access and test the concerned parts.

If you don’t think you’re up to the task, then you shouldn’t hesitate to leave the task to a professional mechanic.

Want to diagnose the problem yourself? Watch the video below to get an idea of what the process might involve:

How to Fix the P0670 Code

When it comes to resolving the problems causing the P0670 error code, your repair process should be based on your diagnosis. The code’s definition and common causes do signify that the problem is related to the glow plugs, but that isn’t always the case so you shouldn’t immediately replace your glow plug control module. Always keep in mind that there isn’t a magic bullet when it comes to fixing diagnostic trouble codes (DTC).

After you’ve identified the culprit, consult trusted internet repair resources and how-to guides. Consulting your repair manual or internet repair databases can also be beneficial because they might have important information regarding your issue.