P0677 code — how to fix error fast

If you own a diesel-powered car, one of the most common OBD2 codes you may encounter during years of service is P0677. This code can have a severe effect on your car’s drivability and even the ability to start the engine, which is why you need an in-depth understanding of the P0677 code meaning.

That’s what we aim to provide for all those among you that aren’t familiar with the code. This guide will include all the necessary bits of information on diagnosing and fixing the code, and we’ll also mention some of the most common triggers of the code along with the preventive measures you can apply.

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What does the P0677 code mean?

The P0677 code is a diagnostic trouble code that indicates a malfunction in the glow plug control circuit. The glow plug is an essential component of a diesel engine that helps to start a cold engine. The code is usually triggered when the powertrain control module (PCM) detects a low voltage or high resistance in the glow plug control circuit.

The code can cause several symptoms, including hard starting, rough idling, and decreased fuel efficiency. If the problem with the glow plug circuit gets too severe, you may not be able to start your engine in cold weather, since that’s when the chamber needs extra heat for proper combustion.

What causes the P0677 code?

Several factors can cause the P0677 code, including faulty glow plugs, damaged wiring, or a malfunctioning control module. Here are some of the most common causes of the P0677 code:

Faulty glow plugs

Glow plugs are essential components of a diesel engine. They heat the engine’s air to make it easier to start in cold weather. If one of the glow plugs is faulty, it can cause the P0677 code. In some cases, the glow plugs may fail due to wear and tear, while in other cases, they may fail due to overheating.

Damaged wiring

The wiring that connects the glow plugs to the control module can become damaged over time. Vibrations, corrosion, or exposure to moisture can cause the wiring to break or become disconnected. When this happens, the control module may not receive the proper signal from the glow plugs, resulting in the P0677 code.

Malfunctioning control module

The control module is responsible for regulating the voltage sent to the glow plugs. If the control module is malfunctioning, it can cause the P0677 code. A malfunctioning control module may send the wrong voltage to the glow plugs, causing them to fail or not operate at all.

Which car models does the P0677 code affect the most?

The P0677 code is most commonly found in diesel engines. Specific car models that are most likely to be affected by the code include the models with a tendency of glow plug circuit faults, so we looked for such models to bring you a complete list:

• Chevy Silverado: The Silverado HD trucks are designed for heavy-duty work and use diesel engines that operate with glow plugs, making them prone to the code P0677.
• Mercedes-Benz Sprinter: The Sprinter is a popular van used for commercial purposes such as delivery and transportation. It is available with a diesel engine that uses glow plugs.
• Dodge RAM: The Ram 2500 and 3500 trucks are known for their powerful diesel engines, but these engines can also experience issues with glow plugs.

How to diagnose the P0677 code

Diagnosing the P0677 code requires a thorough inspection of the glow plug control circuit. Here are the steps to diagnose the code:

Check for other codes

Before diagnosing the P0677 code, check for any other diagnostic trouble codes that may be present. Other codes can help identify underlying issues that may be contributing to the code.

Inspect the glow plugs

Inspect the glow plugs for any visible signs of damage or wear and tear. Check the resistance of each glow plug using a multimeter. If the resistance is outside the manufacturer’s specifications, the glow plug may be faulty and should be replaced.

Check the wiring

Inspect the wiring that connects the glow plugs to the control module. Look for any loose connections, corrosion, or damage. Use a multimeter to test the continuity of the wiring. If the wiring is damaged, it should be repaired or replaced.

Test the control module

Test the control module using a scan tool or multimeter. Check the voltage output of the control module to ensure that it is within the manufacturer’s specifications. If the voltage is incorrect, the control module may be malfunctioning and should be replaced.

How to fix the P0677 code

Once you’ve determined the root cause behind the code, you’ll be able to use the information laid out in this article to fix the code. So, here are some of the most effective solutions depending on what has caused the code in your car:

Replace faulty glow plugs

If the glow plugs are faulty, they should be replaced. Follow the manufacturer’s specifications for the correct type of glow plug and the proper installation procedure.

Repair damaged wiring

If the wiring is damaged, it should be repaired or replaced. Use high-quality wiring and connectors to ensure a reliable connection.

Replace the control module

If the control module is malfunctioning, it should be replaced. Follow the manufacturer’s specifications for the correct type of control module and the proper installation procedure.

How to prevent the P0677 code

Preventing the P0677 code requires regular maintenance of the glow plug control circuit. Here are some preventative measures to take:

• Perform regular glow plug circuit maintenance
• Use high-quality glow plugs
• Avoid overheating the plugs before starting the engine again

Overall, taking proper care of your vehicle should be enough to prevent the code P0677 from emerging again, since glow plugs don’t require so frequent changes as spark plugs in petrol-powered cars.

Our take

In conclusion, the P0677 code is a common issue with diesel engines that can cause significant damage if ignored. By following the steps outlined in this article, you should be able to avoid dealing with this issue ever again and ensure taking the proper steps to fix it for good.