P0678 code — how to fix error fast
Navigating the P0678 code is crucial to ensure your car's optimal performance.
The worst thing that could happen to you as a driver is the inability to start your car, and the P0678 code can indicate just that. It has to do with the operation and power supply of glow plugs within a diesel engine, so if you own a car that runs on diesel, you may need to pay extra attention to the code.
If it already appeared, you’ll need to take some steps to repair the issue behind it and fix it, and that’s just what our guide will help you do. Our team will give you an overview of the P0678 code meaning and the reasons behind it, as well as give you the necessary means to diagnose, fix, and prevent the code in the future.
Why you can trust REREV’s OBD2 code advice: Our automotive expert researchers with experienced mechanics undertakes a thorough research methodology to deliver precise insights on OBD codes. Find out more about OBD2 codes research process..
What does the P0678 code mean?
The P0678 code is a diagnostic trouble code that indicates a problem with the glow plug control circuit. The glow plug control circuit is an essential component of diesel engines that helps in cold weather starting. The code is crucial in diagnosing and fixing any problems that may arise in the glow plug control circuit.
Specifically, it means that the power supply to the glow plug system is insufficient and needs to be checked. The code could also point to some issues with the glow plug control module, which is why you need to be aware of all the possible reasons behind the code.
What causes the P0678 code?
The code P0678 can be triggered by a variety of faulty components in the diesel engine’s ignition system. You can’t simply assume that the circuit is bad or that the glow plug module needs replacement, so here’s a full list of the potential reasons why this code may have appeared:
Faulty glow plugs
Glow plugs are an essential component of diesel engines that help in cold weather starting. Faulty glow plugs can cause the P0678 code to appear. If the glow plugs are not functioning correctly, the engine may have difficulty starting, especially in cold weather. Symptoms of faulty glow plugs include engine misfires, rough idling, and poor fuel economy.
Wiring issues
Wiring issues can cause the P0678 code to appear. If there are any problems with the wiring that connects the glow plug control module to the glow plugs, the engine may have difficulty starting. Symptoms of wiring issues include intermittent starting problems and engine misfires.
Faulty glow plug control module
The glow plug control module is an essential component of the glow plug control circuit. If the module is faulty, it can cause the P0678 code to appear. Symptoms of a faulty glow plug control module include difficulty starting the engine, engine misfires, and poor fuel economy.
Which car models does the P0678 code affect the most?
While this code can be triggered in any diesel engine, there are some car models that are more likely to be affected by it than others.
We decided to do some digging, and the names of these car models popped up when we looked for vehicles that are exposed to this code more than others:
- Ford Super Duty: The Ford Super Duty is a popular choice among truck enthusiasts, but it has been known to experience issues with glow plug circuits. In fact, many Ford owners have reported seeing the P0678 code show up on their dashboards.
- Chevrolet Silverado: The Chevrolet Silverado is another popular truck model that may be affected by the P0678 code. Some Silverado owners have reported issues with glow plug circuits, which can result in difficulty starting the engine.
- Dodge RAM: The Dodge Ram is a third truck model that may experience issues with glow plugs and trigger the P0678 code. Ram owners have reported problems with glow plug circuits, which can result in rough idling or even stalling
How to diagnose the P0678 code
While the code P0678 is often caused by bad electrical connections in the glow plug control circuit, there could be other reasons behind it as you could already see. So, we wanted to give you a brief overview of each method that can be used to diagnose specific causes of this code:
Visual inspection
The first step in diagnosing the P0678 code is often a visual inspection of the glow plug and wiring. You can inspect the wires leading to the glow plugs for signs of damage or wear, and also check to see if the glow plugs themselves are corroded or damaged in any way.
Checking the electrical system
If a visual inspection doesn’t reveal any issues, you can move on to electrical testing. This involves using a multimeter to test the voltage and resistance in the glow plug circuit. By measuring the voltage and resistance, you can determine if there is an issue with the circuit that controls the glow plugs.
Look for other related OBD2 codes
Connecting a diagnostic scanner to the vehicle’s onboard computer system and reading any error codes that are related to this one such as the P0674 or P0675 can also help. This way you can obtain more information on the exact source of the problem and deal with that particular component.
How to fix the P0678 code
Fixing the P0678 code requires identifying the underlying issue and taking the appropriate steps to fix it. Here’s how to fix the code based on the diagnosis you’ve previously set:
Replace faulty glow plugs
If the glow plugs are faulty, you will need to replace them. The cost of replacement depends on the type of glow plugs and the number of cylinders in the engine. Usually, replacing glow plugs ranges between $100 to $300.
Repair wiring issues
If there are any wiring issues, you will need to repair or replace the wiring. The cost of repair or replacement depends on the extent of the damage. On average, the cost of repairing or replacing wiring ranges between $100 to $500.
Replacing the faulty glow plug control module
If the glow plug control module is faulty, you will need to replace it. The cost of replacement depends on the make and model of the car. You’ll be looking at the repair bill of around $300 to $600 for this sort of replacement.
How to prevent the P0678 code
Preventing the P0678 code requires routine maintenance of the glow plug control circuit. Here’s what you can do to prevent the code from appearing:
- Replace the glow plugs at regular intervals
- Inspect the wiring regularly for any signs of damage or wear
- Replace the glow plug control module at regular intervals
- Perform routine maintenance on the engine to ensure that it’s running correctly
With these prevention steps, it’s unlikely that you’ll ever have to bother with the code P0678 again and you can prevent issues with starting your car in cold weather.
Our take
Ultimately, the code P0678 is often overlooked by drivers and that can negatively reflect on the engine’s performance and even the ability to start. That’s why you should always stick by the diagnostic and fixing methods we’ve mentioned, as well as other details from this guide that can help you remove the code and prevent it in the future.
How serious is the P0678 code?
While the P0678 code may not necessarily prevent your engine from running, it can lead to difficulty starting the engine and poor performance while driving. In some cases, it may even cause the engine to stall. As such, it’s important to have this issue diagnosed and repaired as soon as possible.
Can I still drive my vehicle with the P0678 code?
It’s generally safe to drive your vehicle with the P0678 code, but you may experience difficulty starting the engine or poor performance while driving. Continuing to drive your vehicle with this issue could lead to further damage down the line, so it’s best to have it diagnosed and repaired as soon as possible.
How is the P0678 code repaired?
Depending on the specific issue causing the P0678 code, repairs may involve replacing damaged wiring, cleaning corroded parts, or replacing faulty components such as relays or control modules.
