P0148 / P014800 is an OBD fault code related to fuel delivery.

🔧 P0148 / P014800 – Fuel Delivery Error

General Meaning

Fuel delivery system malfunction
The ECU detects fuel pressure not matching the requested value.

> Common on diesel vehicles (especially common-rail systems), but can appear on some petrol direct-injection cars too.

🚗 Common Symptoms

Hard starting or no start

Engine stalls

Loss of power / limp mode

Excessive smoke (diesel)

Rough idle

Check Engine Light ON

⚠️ Most Common Causes

1. Fuel Pressure Too High or Too Low

Faulty high-pressure fuel pump (HPFP)

Worn internal pump components

Metal debris in fuel system (very common on diesel)

2. Fuel Pressure Regulator Fault

Regulator stuck open/closed

Electrical failure

Contaminated with debris

3. Fuel Rail Pressure Sensor

Incorrect signal to ECU

Wiring issue (5V reference / signal / ground)

Sensor drift

4. Fuel Supply Problems

Blocked fuel filter

Air in fuel lines

Weak low-pressure pump

Contaminated fuel

5. Wiring / ECU Issues

Corroded connectors

Broken wiring near rail sensor or regulator

Rare: ECU fault

🧪 Recommended Diagnostic Steps (Workshop Flow)

Step 1: Scan Tool Data

Check actual vs requested fuel rail pressure

Look at:

During cranking

Idle

Under load

👉 If deviation is large → mechanical issue likely

Step 2: Check Low-Pressure Side

Measure supply pressure before HPFP

Replace fuel filter if in doubt

Check for air bubbles (transparent line if equipped)

Step 3: Rail Pressure Sensor Test

Check:

5V reference

Signal voltage change with RPM

Compare scan tool reading with mechanical gauge if possible

Step 4: Pressure Regulator / Metering Valve

Command test (if scan tool allows)

Check resistance values

Inspect for metal particles

⚠️ Metal shavings = HPFP failure → full system cleaning required

Step 5: Wiring Inspection

Especially near:

Fuel rail

HPFP

Engine vibration points

🚨 Important Diesel Warning

If you see metal particles in fuel:

Do NOT replace only the pump

You must:

Flush fuel lines

Clean/replace rail

Replace injectors (often required

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