Is P0094 always a pump fault?

No. Excessive injector back-leak is one of the most common causes of rail-pressure faults on high-mileage diesels — always run a leak-off comparison before replacing the pump.

Why does the fault appear mainly when hot?

Diesel thins as it warms, so marginal internal leaks in injectors and regulators flow more when hot. A warm-engine test catches faults a cold test misses.

Can a blocked filter trigger this code?

Yes. A starved low-pressure side stops the high-pressure pump building demand pressure. Check the filter and supply before high-cost parts.

P0094 Fuel System Leak Detected — Small Leak — Causes & Fix

What Does P0094 Mean?

P0094 is the small-leak sibling of P0093: the ECU's model shows pressure escaping somewhere at a modest rate. Internal injector back-leak is the classic cause because there is nothing visible to see — a measured leak-off comparison finds it in minutes.

P0094 at a Glance

What it means: The ECU's pressure model detects a small leak in the fuel system.
Most common cause: Excessive injector back-leak
Severity: Moderate to serious — rail-pressure faults cause power loss and non-starts.
Can you drive?: Short distances in limp mode only. Diagnose promptly.
Typical repair cost: £40-£150 for sensor/regulator work; £100-£350 per injector where back-leak is the cause.

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P0094 Fuel System Leak Detected — Small Leak — Causes & Fix

What Does P0094 Mean?

P0094 at a Glance

Find the Exact Fuel Injectorby Vehicle Registration

Find the Exact Fuel Injector
by Vehicle Registration