If you are getting the P1351 fault code on your Peugeot, you are not alone! this a common problem with the diesel variants of the Peugeot, whether you have the 1.4 HDI, 1.6 HDI, or the 2.0 HDI, all of these engine variants suffer from the same issue.
In this article, I will explain the problem, what is causing this fault code to appear, and how to fix it based on my experience as a mechanic.
What Does P1351 Fault Code Mean on a Peugeot?
Before we get into the details of what causes this fault code to appear and how to fix it, let’s look more closely at what this code means in general.
The P1351 fault code is triggered when your Peugeot’s ECU (Engine Control Unit) detects an issue with the vehicle’s powertrain.
What Causes Peugeot P1351 Code?
Now, let’s look at the main causes. In theory, there are many different reasons why your ECU might throw the P1351 fault code, but from working with many Peugeots it boils down to two main causes which are bad glow plugs and a faulty heating relay circuit.
1. Bad Glow Plugs (One or More)
This is the most common cause of this error code (I would say 90-95% of the time its the main p1351 code cause). If one or more of your glow plugs has failed, then you will likely see this fault appear.
The reason for this is that when the engine starts to warm up and needs more power, these glow plugs come into play. They heat up in order to ignite fuel which powers your vehicle.
2. Faulty Heater Relay Circuit
Another cause for P1351 error code on a Peugeot is a Faulty heater relay circuit. This is not as common of a cause as bad glow plugs, but it does happen.
When this circuit is faulty it will cause your vehicle to stall out and throw the P1351 error code.
What are Glow Plugs, and Why Do They Matter?
Since the Peugeot P1351 code is commonly caused by one or more bad glow plugs. I want to take a minute to discuss what glow plugs are, and why they matter on your Peugeot.
Glow Plugs are a heating element that ignites your vehicle’s fuel. They are located inside the engine of your vehicle and are used to warm up the engine before starting it.
This warming process occurs when you start your car, which is why sometimes it takes longer than usual for your Peugeot to start up after sitting overnight.
Glow plugs are only found in diesel engines of the Peugeot whereas the petrol engines use spark plugs instead.
Importance of Glow Plugs on Your Peugeot
Glow plugs are an essential component in diesel engines like the ones in Peugeot vehicles, they work as heating elements and heat the incoming fuel and air to ensure efficient combustion of fuel.
Each cylinder in the engine has one glow plug, either in the pre-chamber or in the combustion chamber.
The control unit that regulates the operation of the glow plugs is also important. it keeps the glow plugs on for a while after starting the engine to ensure optimal combustion of the fuel and lower emissions.
This can help to improve the performance of your diesel engine
Why Do Peugeots Glow Plugs Fail?
Now, that I have briefly explained what these are and the role they play on an engine, let’s look at why glow plugs go bad on your Peugeot which results in the P1351 fault code.
- Extremely High Engine Voltage:
- Incompatible Glow Plugs for the Engine
- Carbon Build Up
- Wrong Relay Installed
- Wear and Tear (overtime)
Other Signs of Bad/Failing Glow Plugs
Other than the P1351 fault code, there are several other signs that your Peugeot glow plugs might be bad. Here are just a few:
Increased Average Fuel Consumption
When your Peugeot glow plugs fail, it can cause your engine to run rough and inefficiently. This will result in an increase in the amount of fuel consumed by your vehicle.
The more fuel your engine burns, the dirtier it gets which causes more carbon build-up on the intake valves. In turn, this makes them sticky which leads to poor combustion and reduces power output.
Smoke Coming Out of Your Exhaust
When you see smoke coming out of your exhaust (whether black or white) it can be an indicator that one or more glow plugs need replacing.
The smoke is from unburnt fuel that is being released from your engine which means it’s not getting burned properly.
Engine Misfire and Rough Idling
If your vehicle is misfiring or rough idling, it’s likely due to a faulty glow plug. an engine misfire is when one or more of your engine’s cylinders are not firing properly.
Which can lead to reduced power output and engine vibrations, and sluggish throttle response.
Your Peugeot takes longer to start
If you are experiencing hard starts and long cranking before the engine starts, is another indication that your glow plugs are going bad.
How to Fix Code P1351 on a Peugeot
The most common way to fix P1351 is to replace the faulty glow plug (I personally recommend replacing it all at once).
If you have a multimeter, use it to test each glow plug and see if any of them are bad. Here is a video demonstrating how to test and replace glow plugs on a Peugeot