What Does Code P1351 Mean on a Peugeot?

If your Peugeot is showing the P1351 fault code, don’t panic. This is one of the most common codes on Peugeot diesel engines.

I’ve worked on dozens of Peugeots with this exact code. Most of the time, it’s a simple fix. But you need to know what’s causing it before you start throwing parts at the car.

In this guide, I’ll explain what P1351 means, what causes it, and how to fix it. I’ll also share some tips that could save you time and money.

What Is the P1351 Code?

The P1351 code on a Peugeot means there’s a problem with the glow plug preheating system.

More specifically, it points to a fault in the glow plug relay circuit. The car’s computer (ECU) has detected that something isn’t working right in this system.

Here’s what you need to understand: Peugeot diesel engines use glow plugs to help start the engine. These plugs heat up the air inside the cylinders. This makes it easier for diesel fuel to ignite, especially in cold weather.

The glow plug relay controls when these plugs turn on and off. When this relay or the plugs themselves fail, you get the P1351 code.

This is a manufacturer-specific code. That means it only applies to certain brands. On Peugeot and Citroën vehicles, P1351 always relates to the glow plug system.

Which Peugeot Models Are Affected?

The P1351 code is extremely common on Peugeot HDi diesel engines.

Here are the models I see most often with this code:

Peugeot 206 1.4 HDi and 1.6 HDi
Peugeot 207 1.6 HDi
Peugeot 307 1.6 HDi and 2.0 HDi
Peugeot 308 1.6 HDi
Peugeot 407 1.6 HDi and 2.0 HDi
Peugeot 3008 1.6 HDi
Peugeot 5008 1.6 HDi
Peugeot Partner 1.6 HDi
Peugeot Expert 1.6 HDi and 2.0 HDi

If you drive a Citroën with the same HDi engine, you might see this code too. These engines are shared between both brands.

Symptoms of P1351

Not everyone with the P1351 code will notice problems. Some cars run perfectly fine. Others show clear signs of trouble.

Here are the most common symptoms:

Check engine light on. This is often the first and only sign. The engine warning light stays on, but the car still runs okay.

Hard starting in cold weather. The car takes longer to start when it’s cold outside. You might have to crank it several times before it fires up.

Rough idle when cold. The engine shakes or vibrates more than usual right after starting. This usually goes away once the engine warms up.

Engine goes into limp mode. In some cases, the car limits your speed and power. This is the ECU protecting the engine from damage.

Poor fuel economy. The engine doesn’t burn fuel as efficiently. You might notice you’re filling up more often.

Black or white smoke from exhaust. Unburnt fuel can cause visible smoke, especially when starting the car.

Glow plug warning light issues. The coil-shaped light on your dashboard might not come on at all. Or it might stay on longer than normal.

Main Causes of P1351

From my experience, there are four main reasons for the P1351 code.

1. Worn Out Glow Plugs

This is the most common cause. Glow plugs don’t last forever. They typically need replacing every 100,000 to 150,000 kilometres (about 60,000 to 95,000 miles).

When a glow plug fails, it either stops working completely or doesn’t heat up properly. The ECU detects this and throws the P1351 code.

Here’s the tricky part: Even one bad glow plug can trigger the code. And if one is failing, the others are probably close behind.

2. Faulty Glow Plug Relay

The relay is an electrical switch that sends power to the glow plugs. When it fails, the plugs don’t get the power they need.

On most Peugeots, this relay is located in the engine bay. It’s usually near the battery or the engine fuse box. Some call it the “glow plug controller” because it does more than just switch power on and off.

A faulty relay can cause all the glow plugs to stop working at once. Or it might work intermittently, causing starting problems only sometimes.

3. Wiring Problems

The wires connecting the relay to the glow plugs can corrode or break over time. This is more common in older cars or those driven in harsh conditions.

Look for:

Corroded connectors
Broken wires
Loose connections
Damaged insulation

These problems can be hard to spot. But they’re worth checking before you replace expensive parts.

4. Blown Fuse

This is the simplest cause. A blown fuse stops power from reaching the glow plug system.

Check your owner’s manual for the location of the glow plug fuse. It’s usually in the main fuse box under the bonnet.

Less Common Causes

Sometimes the problem isn’t the glow plug system at all. Rare causes include:

ECU (engine control unit) fault
Poor ground connection
Software glitch that needs a reset

How to Diagnose P1351

Before you start replacing parts, you need to find out what’s actually wrong.

Step 1: Read the Fault Codes

Use an OBD-II scanner to confirm the P1351 code. A basic scanner will show the code. But a Peugeot-specific tool (like Lexia or DiagBox) gives more detailed information.

Write down any other codes that appear. Sometimes P1351 shows up with other faults that point to the real problem.

Step 2: Check the Fuse

This takes two minutes and costs nothing.

Find the glow plug fuse in your fuse box. Pull it out and check if the metal strip inside is broken. Replace it if it’s blown.

If the new fuse blows immediately, you have a short circuit somewhere. Don’t keep replacing fuses—find the short first.

Step 3: Test the Glow Plugs

You’ll need a multimeter for this. Set it to measure resistance (ohms).

Here’s how to test each glow plug:

Disconnect the wire from the top of the glow plug.
Put one multimeter lead on the glow plug terminal.
Put the other lead on a good ground (like the engine block).
Check the reading.

A good glow plug should read between 0.5 and 2 ohms. If you get no reading at all, the plug is dead. If the reading is very high (above 6 ohms), the plug is failing.

Test all four (or however many your engine has). They should all show similar readings. One plug that reads differently from the others is likely bad.

Step 4: Check the Relay

The glow plug relay is harder to test without proper equipment.

On some Peugeots, you can hear the relay click when you turn on the ignition. No click could mean a bad relay. But newer solid-state relays don’t click at all.

The best way to test the relay is with a diagnostic tool that can run an actuator test. This turns the relay on manually while you check for voltage at the glow plugs.

Step 5: Inspect the Wiring

Look at all the wires running from the relay to the glow plugs.

Check for:

Green or white corrosion on connectors
Wires that look burnt or melted
Loose or damaged plugs

Pay special attention to the main engine connector. This large plug carries power to many systems, including the glow plugs. A bad connection here causes lots of problems.

How to Fix P1351

The fix depends on what’s causing the code. Here are the most common repairs.

Replacing Glow Plugs

This is the most common fix. And it’s one you can do yourself if you’re handy with tools.

What you’ll need:

New glow plugs (OEM quality recommended—Bosch, NGK, or Beru)
Deep socket (usually 10mm or 12mm)
Ratchet with extension
Penetrating oil
Torque wrench

Important tips:

Warm up the engine slightly before removing the plugs. This helps them come out easier.
Soak the plugs with penetrating oil and let it sit for at least 15 minutes.
Remove the plugs slowly. Don’t force them. A snapped glow plug is a nightmare to extract.
Torque new plugs to spec (usually 15-20 Nm). Don’t overtighten.

On some HDi engines, the glow plugs are at the back of the engine. This makes access difficult. You might need to remove the air filter box, EGR valve, or other parts to reach them.

If you’re not comfortable with this, have a mechanic do it. The labour cost is worth it to avoid snapping a plug.

Replacing the Glow Plug Relay

The relay is easier to replace than the glow plugs in most cases.

Where to find it:

On most Peugeots, the relay is in the engine bay. Common locations include:

Behind the battery
Near the engine fuse box
On the left side of the engine bay (passenger side in UK)

Replacement is straightforward:

Disconnect the battery.
Unplug the connector from the old relay.
Remove the mounting bolt or clip.
Install the new relay.
Reconnect everything.

Always use an OEM relay or a quality aftermarket one. Cheap relays often fail quickly.

Fixing Wiring Issues

If you find corroded or damaged wires, you have a few options:

Clean corroded connectors with electrical contact cleaner.
Repair broken wires with proper automotive splices.
Replace damaged sections of the wiring harness.

For serious wiring damage, you might need to run new wires directly from the relay to the glow plugs. This bypasses any damaged sections in the main harness.

Clearing the Code

After you’ve fixed the problem, you need to clear the fault code.

Use your OBD-II scanner to erase the code. Then drive the car for a few days. If the code comes back, the problem isn’t fixed.

Repair Costs

Here’s what you can expect to pay for P1351 repairs:

Glow plugs (parts only): £40 to £120 for a set of four. OEM plugs cost more but last longer.

Glow plug relay (parts only): £30 to £80 depending on the model.

DIY total cost: £40 to £200 if you do the work yourself.

Garage repair: £150 to £400 depending on what needs replacing and how hard it is to access.

If the glow plugs are hard to reach (like on the 2.0 HDi), labour costs go up significantly.

Common Mistakes to Avoid

I’ve seen people make these mistakes when dealing with P1351.

Mistake 1: Only replacing one glow plug. If one plug failed, the others are probably tired too. Replace them all at once. This saves you from doing the job twice.

Mistake 2: Using cheap parts. Bargain-bin glow plugs and relays often fail within months. Stick with quality brands like Bosch, NGK, or Beru.

Mistake 3: Ignoring the code because the car runs fine. On HDi engines with a DPF (diesel particulate filter), glow plugs help with regeneration. If they don’t work, your DPF can get clogged. That’s an expensive problem.

Mistake 4: Forcing out stuck glow plugs. A snapped glow plug means removing the cylinder head in the worst case. Take your time. Use penetrating oil. Apply heat if needed.

Mistake 5: Not checking the wiring. I’ve seen people replace plugs and relays when the real problem was a corroded connector. Five minutes of inspection could save you a lot of money.

Mistake 6: Clearing the code without fixing the problem. The code will come back. And the underlying issue might get worse.

FAQs

Can I still drive with the P1351 code?

Yes, in most cases. The car will still run. But you might have trouble starting in cold weather. If the engine goes into limp mode, you should fix it soon.

Will P1351 cause my car to fail an MOT?

The engine warning light being on will cause an MOT failure in the UK. Even if everything else passes, the light needs to be off.

Do glow plugs affect running, or just starting?

Mainly starting. Modern diesel engines don’t really need glow plugs once they’re warm. But on cars with a DPF, the glow plugs help with filter regeneration while driving.

How long do Peugeot glow plugs last?

Typically 100,000 to 150,000 km. Some last longer, some fail earlier. It depends on driving conditions and quality of the plugs.

Can I test glow plugs without removing them?

Yes. You can test resistance with a multimeter while they’re still in the engine. Just disconnect the power wire first.

Is P1351 serious?

It’s moderately serious. You won’t break down immediately. But ignoring it can lead to hard starting, DPF problems, and poor fuel economy.

Why does P1351 keep coming back after I’ve fixed it?

Either the fix didn’t address the real cause, or there’s an intermittent fault. Try using a Peugeot-specific diagnostic tool for more details.

Should I replace all four glow plugs at once?

Yes. If one has failed, the others are probably close behind. Replacing them all saves you from doing the job again in a few months.

Final Thoughts

The P1351 code on a Peugeot usually points to worn glow plugs or a faulty relay. Both are fixable without spending a fortune.

Start with the basics: check the fuse, test the glow plugs with a multimeter, and inspect the wiring. Most of the time, replacing the glow plugs solves the problem.

Don’t ignore this code, especially if you have a car with a DPF. The glow plugs play a role in keeping that filter clean. A clogged DPF is far more expensive to fix than a set of glow plugs.

If you’re not confident working on your car, take it to a mechanic. Just make sure they diagnose the problem properly before replacing parts.

Quick summary of what to do:

Scan for fault codes and confirm P1351.
Check the glow plug fuse.
Test each glow plug with a multimeter.
Inspect the relay and wiring.
Replace faulty parts with quality components.
Clear the code and test drive.

That’s everything you need to know about the P1351 code on Peugeot vehicles. Fix it once, fix it right, and your diesel will keep starting reliably for years to come.