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Code P1434

Symptoms

• Check Engine Light is on

• Fuel smell from the vehicle

• Failed emissions test

Common Causes

• Faulty DM TL pump

• Damaged or loose fuel cap

• Cracked or damaged EVAP hoses

Glossary

DM TL: Diagnostic Module Tank Leakage

EVAP: Evaporative Emission Control System

Related Codes

• P0455

• P0456

Official description

Diagnostic Module Tank Leakage (DM TL)

Laymans terms

This code means that the car's computer thinks there might be a leak in the system that holds the fuel vapors. It's like having a tiny hole in a balloon that lets air out slowly.

Explanation

The P1434 code is triggered when the vehicle's diagnostic module detects a potential leak in the evaporative emission control system, which is responsible for capturing fuel vapors.

Technical description

The Diagnostic Module Tank Leakage (DM TL) monitors the evaporative emission system for leaks. It uses a pump to pressurize the system and checks for pressure drops that would indicate a leak. If a leak is detected, the P1434 code is set.

Diagnosis steps

• Inspect the fuel cap for damage or looseness.

• Check EVAP hoses for cracks or disconnections.

• Test the DM TL pump for proper operation.

Repair procedures

• Replace or tighten the fuel cap.

• Repair or replace damaged EVAP hoses.

• Replace the DM TL pump if faulty.

Tools required

• OBD-II scanner

• Vacuum pump

• Multimeter

Estimated repair cost

$100 - $300

Difficulty level

Moderate

Commonly affected vehicles

• BMW 3 Series

• BMW 5 Series

• Mini Cooper

Preventive measures

• Regularly check and tighten the fuel cap.

• Inspect EVAP system components during routine maintenance.

• Use quality fuel caps and components.

Error code type

Emissions Control Issue

User experience recommendations

• Do not ignore the Check Engine Light.

• Have the vehicle inspected by a professional if you smell fuel.

• Regular maintenance can prevent this issue.

Warranty information

Check with your vehicle manufacturer for emissions-related warranty coverage.

Historical data

The P1434 code has been more prevalent in vehicles with advanced evaporative emission control systems, especially in European models.

Urgency level

Moderate – While not immediately critical, it can affect emissions and fuel efficiency.

Legal and safety notice

Driving with an emissions-related fault may not be legal in areas with strict emissions regulations.

Testing conditions

• Engine at operating temperature

• Vehicle parked on a level surface

Component location

The DM TL pump is usually located near the fuel tank or in the rear of the vehicle.

FAQs

Q: Can I drive my car with a P1434 code?
A: Yes, but it's best to address the issue soon to avoid emissions problems.

Q: Will a loose gas cap cause a P1434 code?
A: Yes, a loose or damaged gas cap can trigger this code.

Last updated: Jan 16, 2026 • Source: internal database
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