Worn or fouled spark plugs, especially if maintenance intervals have been exceeded; Faulty ignition coils or coil-on-plug boots that cause weak or intermittent spark; Vacuum leaks from cracked intake hoses or worn gaskets, leading to lean misfire; Clogged or failing fuel injectors that deliver inconsistent fuel volume; Low fuel pressure from a weak pump or restricted filter, affecting all cylinders; Mechanical issues such as low compression from worn rings or valve problems; Faulty crankshaft position sensor or reluctor ring causing erratic misfire detection

DTC codes / Jaguar codes / P1315

P1315 · JaguarPersistent Misfire

Q: What does code P1315 mean?

Persistent Misfire. P1315 on Jaguar vehicles indicates that the engine control module (ECM) has detected a persistent misfire that has exceeded the threshold for a specific cylinder or the entire engine, often after multiple drive cycles. The ECM monitors crankshaft speed fluctuations and identifies when a cylinder fails to contribute power consistently, storing this code when the misfire is severe enough to risk catalyst damage or drivability issues.

P1315 on Jaguar vehicles indicates that the engine control module (ECM) has detected a persistent misfire that has exceeded the threshold for a specific cylinder or the entire engine, often after multiple drive cycles. The ECM monitors crankshaft speed fluctuations and identifies when a cylinder fails to contribute power consistently, storing this code when the misfire is severe enough to risk catalyst damage or drivability issues.

SystemPowertrain

Code typeJaguar specific

SeverityHigh

Fix difficultyProfessional

AreaIgnition system and misfire

Symptoms you may notice

Illuminated or flashing check engine light, especially under acceleration or load
Noticeable engine shaking or rough idle, particularly when cold or at low speeds
Loss of power or hesitation during acceleration, often described as a 'stumble'
Reduced fuel economy due to incomplete combustion
Often no symptoms besides the warning light if the misfire is intermittent or mild
Possible rotten egg smell from the exhaust if unburned fuel reaches the catalytic converter

Common causes, most likely first

Worn or fouled spark plugs, especially if maintenance intervals have been exceeded
Faulty ignition coils or coil-on-plug boots that cause weak or intermittent spark
Vacuum leaks from cracked intake hoses or worn gaskets, leading to lean misfire
Clogged or failing fuel injectors that deliver inconsistent fuel volume
Low fuel pressure from a weak pump or restricted filter, affecting all cylinders
Mechanical issues such as low compression from worn rings or valve problems
Faulty crankshaft position sensor or reluctor ring causing erratic misfire detection

How to diagnose and fix it

Scan all modules for stored codes and freeze-frame data to identify which cylinder(s) are misfiring and under what conditions
Inspect spark plugs for wear, fouling, or incorrect gap, and replace them if they are due or damaged
Swap ignition coils between cylinders to see if the misfire moves, confirming a faulty coil
Perform a smoke test to check for vacuum leaks in the intake system and repair any leaks found
Test fuel pressure and injector pulse width, and clean or replace injectors if flow is inconsistent
Run a compression test and cylinder leak-down test to rule out mechanical faults if ignition and fuel checks pass
Repair the root cause, clear the codes, and complete a drive cycle to verify the misfire is resolved and the code does not return

Jaguar P1315 misfire diagnosis pitfalls

A flashing check engine light with P1315 means the misfire is severe enough to damage the catalytic converter, so driving should be minimized until repaired.
Jaguar engines are sensitive to spark plug brand and gap; using incorrect plugs can cause persistent misfire codes even when new.
A vacuum leak at the intake manifold gasket on V8 models often causes a lean misfire that mimics a faulty coil, so smoke testing is essential.
The code may set without any drivability symptoms if the misfire occurs only under specific load or temperature conditions, leading to misdiagnosis as a sensor fault.
Always check for technical service bulletins (TSBs) for the specific Jaguar model and engine, as some misfire issues are addressed by software updates or revised parts.

Can I keep driving with P1315?

If the check engine light is flashing, stop driving as soon as safely possible to avoid catalytic converter damage; if it is steady, drive gently and avoid heavy acceleration until the misfire is diagnosed and repaired.

Tools that help

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Guidance is general and written for Jaguar vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.