P0446 on 2012-2019 BMW 3-Series: EVAP Vent Circuit Causes and Fixes

What's Unique About the 2012-2019 BMW 3-Series

While P0446 is a universal code, on modern BMWs like the F30 3-Series, the EVAP system uses a specific component called a Diagnostic Module for Tank Leakage (DMTL) pump. This module combines the vent valve function with a small pump to pressurize the system for leak checks. However, a more common failure point that triggers this code on the F30 platform is the separate Fuel Tank Vent Valve (often called a purge valve) located in the engine bay. This valve can fail internally, causing a circuit fault or improper vapor flow. BMW has issued extended warranties for this specific valve on certain models due to a high failure rate.

Generation note: The 2012-2019 year range primarily covers the F30/F31/F34 generation of the BMW 3-Series. The causes and fixes are generally consistent across this generation for all engines offered (N20, N26, N55, B46, B58), as they use a similar EVAP system design.

Symptoms You May Notice

• Check Engine Light is on
• Slightly rough idle, sometimes intermittent
• Difficulty starting the engine immediately after refueling; the engine may crank longer or stumble before catching.
• Fuel pump nozzle clicks off repeatedly when trying to fill the gas tank
• A quiet or absent clicking/ticking noise from the vent valve in the engine bay while the engine is running

Most Likely Causes

1. Failed Fuel Tank Vent Valve (Purge Valve) 🔴 High Probability This valve, located in the engine bay, is a known high-failure item on many BMWs of this era, including the F30 3-Series with N20, B46, and B58 engines. BMW has issued a warranty extension (SI B01 04 19) for this part on certain models due to material and operational issues, confirming its propensity to fail.
   How to confirm: A professional scan tool can activate the valve to listen for a clicking sound. A simpler method is to listen to it with the engine running; a healthy valve makes a steady ticking noise. You can also remove the valve and try to blow through it; if air passes, it's stuck open and faulty. A faulty valve is the confirmed fix in numerous owner forums.
   Typical fix: Replacement of the fuel tank vent valve. This is a simple DIY job taking less than 30 minutes, requiring no special tools.
   Est. part cost: $25-$60
2. Failed DMTL (Diagnostic Module for Tank Leakage) Pump 🟡 Medium Probability The DMTL pump is a core component of the BMW EVAP system and is a frequent failure point across many models. It contains a small motor and electronics located under the car behind the rear passenger-side wheel well liner, where it is exposed to road debris and moisture, leading to failure over time.
   How to confirm: Diagnosis requires a BMW-specific scan tool (like ISTA) to run the EVAP system test, which directly commands the pump to run. A mechanic can also check for power and ground at the pump's electrical connector. Failure of this pump is a less common cause for P0446 than the engine bay vent valve, but it is the next logical part to check.
   Typical fix: Replace the DMTL pump, which is located near the charcoal canister under the rear of the vehicle. This requires removing the wheel and fender liner for access.
   Est. part cost: $40-$100
3. Loose or Faulty Gas Cap ⚪ Low Probability While a loose gas cap typically sets a small leak code (like P0456) rather than a circuit code, a faulty cap with a cracked seal can contribute to EVAP system pressure issues. It's a simple and free first check, though rarely the root cause for P0446 on this platform.
   How to confirm: Ensure the gas cap is tightened until it clicks at least once. Inspect the rubber O-ring on the cap for cracks, dirt, or signs of degradation. If the seal is compromised, the cap should be replaced.
   Typical fix: Tighten or replace the gas cap.
   Est. part cost: $20-$40

Rare But Worth Checking

• Damaged Wiring: Rodents can chew through the wiring for the DMTL pump or the engine bay vent valve, causing an open or short in the circuit. A visual inspection of the harnesses is recommended if replacing parts does not solve the issue.
• Clogged Charcoal Canister: If the charcoal canister becomes saturated with fuel (often from overfilling the gas tank) or its filter gets clogged with debris, it can restrict airflow and cause the DMTL pump to report a fault.
• Cracked EVAP Hoses: The plastic and rubber lines connecting the various EVAP components can become brittle over time and develop small cracks, leading to leaks that can sometimes manifest as a P0446 code.

Diagnosis Steps

1. Read the codes with an OBD-II scanner to confirm P0446 is present. Note any other generic (P-codes) or BMW-specific codes.
2. Inspect the gas cap. Ensure it is tight and the seal is in good condition. Clean any debris from the seal and filler neck.
3. Locate the Fuel Tank Vent Valve in the engine bay, on the side of the intake manifold. With the engine running, listen for a steady clicking sound. A loud, irregular noise or no noise can indicate failure. You can also touch it to feel for the ticking.
4. If you have a capable scan tool, command the vent valve (often called 'tank ventilation valve' or 'TEV' in software) to open and close to verify its operation.
5. If the vent valve is the suspected cause, replace it. It is the most probable fix and a relatively inexpensive part.
6. If the code returns, visually inspect the wiring going to the vent valve and the DMTL pump for any signs of damage.
7. Raise the rear of the vehicle and remove the passenger-side rear wheel and fender liner to access the DMTL pump and charcoal canister.
8. Inspect the DMTL pump and its connector for corrosion, damage, or chewed wires. Check that all hoses are securely connected.
9. The most definitive test for the rest of the system is to use a BMW-specific scan tool to initiate the EVAP system leak test, which will test the DMTL pump's function directly.
10. If tests point to the DMTL pump, replace it.

Parts You'll Likely Need

• Fuel Tank Vent Valve (Purge Valve) (OEM #13907643106) — This is the most common failure part for P0446 on the F30 platform, often failing internally and causing a circuit or performance fault. It is shared across B46, B48, and B58 engines.
  Trusted brands: Bosch, Genuine BMW
  OEM price range: $45-$60
  Aftermarket price range: $25-$40
• DMTL Pump (Leak Diagnostic Module) (OEM #16137333302) — This pump is the second most likely cause. Its failure prevents the EVAP system from being able to self-test, triggering a circuit malfunction code. The part is often made by Bosch for BMW.
  Trusted brands: Bosch, URO Parts, Genuine BMW
  OEM price range: $80-$120
  Aftermarket price range: $40-$70

Related Codes That Often Appear With This One

• P0440 — P0440 indicates a general EVAP system malfunction. It often appears alongside P0446 because the vent circuit failure is a type of general system malfunction.
• 190F08 / 191C02 — These are BMW-specific fault codes that often accompany the generic P0446. They translate to 'Fuel tank ventilation system, malfunction' and 'Tank ventilation system, inlet point malfunction,' pointing directly to the vent valve and related lines.

Technical Service Bulletins (TSBs) & Recalls

• SI B01 04 19: Extended warranty for the EVAP system's vent (purge) valve on certain models, which can cause rough running and trigger EVAP fault codes.
• SI B13 02 12: Service bulletin for F10 5-Series with N20 engine (related to F30) for fault 191C02, caused by a defective fuel tank ventilation valve.

Platform-Specific Known Issues

• BMW has issued an extended warranty (SI B01 04 19) for the fuel tank vent valve on certain 2017 models with the B46 engine, extending coverage to 15 years/150,000 miles in some states. This indicates a known high failure rate for this part.
• An earlier TSB (SI B13 02 12) for the N20 engine also identified a defective fuel tank ventilation valve as the cause for a related fault code (191C02), requiring replacement of the valve and associated lines.

Mechanic-Grade Diagnostic Values

• DMTL Pump Power Supply — expected: 12V with key on, engine off.. Failure: No voltage or low voltage indicates a wiring or fuse issue upstream of the pump.
• Fuel Tank Vent Valve (TEV) Solenoid Resistance — expected: Approximately 20-30 Ohms. (Note: This is a general value for Bosch solenoids; BMW does not publish an official spec. Comparison to a new part is the best test).. Failure: A reading of infinity (open circuit) or near zero (short circuit) indicates a failed solenoid coil.

Hidden / Shadow Codes Worth Checking

• 190F08: Fuel tank ventilation system, malfunction. This is a direct BMW translation that often accompanies P0446 and points to a general EVAP system fault, frequently the tank vent valve. (see via BMW-specific scan tools like ISTA, Foxwell, or advanced OBD-II scanners with manufacturer-specific code reading capabilities.)
• 191C02: Tank ventilation system, inlet point malfunction (or 2nd discharge point). This code is more specific and often isolates the fault to the fuel tank vent valve (purge valve) in the engine bay. (see via BMW-specific scan tools like ISTA, Foxwell, or advanced OBD-II scanners with manufacturer-specific code reading capabilities.)
• 2A17: DMTL module fault. This code indicates the entire DMTL pump module failed to start its test routine, pointing directly to a failure of the pump itself or its power supply. (see via BMW-specific scan tools like ISTA.)

Scan Tool Commands That Help

• ISTA (Rheingold): Component Triggering: 'Motor of diagnostic module' (DMTL) — Use this to directly command the DMTL pump motor to run. You should be able to hear the pump activate when triggered. This confirms the motor works and is receiving a signal.
• ISTA (Rheingold): Component Triggering: 'Changeover valve of diagnostic module' (DMTL) — This tests the internal valve within the DMTL pump assembly. A clicking sound should be audible, confirming the valve solenoid is functional.
• ISTA (Rheingold): ABL Fuel tank system leak test — This is the complete, automated EVAP system test. It runs the DMTL pump to pressurize the system and monitors for pressure decay to detect major and minor leaks. It's the most comprehensive way to verify the entire system's integrity after a repair.

Wiring & Ground Locations

• DMTL Pump Connector — Behind the passenger side rear wheel well liner, connected to the DMTL pump which is attached to the charcoal canister.. This connector is the primary point for testing power and ground to the DMTL pump. Corrosion or damage here can cause a P0446 circuit code.
• Fuel Tank Vent Valve Connector — In the engine bay, attached to the vent valve on the side of the intake manifold.. This is the connection point for the most common failure part. A quick check for voltage here can confirm if the circuit is live before replacing the valve.
• Rear Fuse Box — In the trunk on the right side, behind a trim panel, above the battery.. This fuse box contains the fuse for the EVAP system components, including the DMTL pump. A blown fuse here will cause a circuit fault.

Real Owner Repair Stories

• f30.bimmerpost.com user (2016 BMW 340i xDrive) — Persistent P0446 check engine light.
  ❌ Tried (didn't work) Clearing the code with a scan tool., Cleaning the gas cap.
  ✅ What actually fixed it The dealer diagnosed and replaced the 'gas tank evap valve' (the fuel tank vent valve in the engine bay) under warranty, which resolved the code.
• 2Addicts forum user (2017 M240i xDrive (B58 engine, similar EVAP to F30), 40,674 miles) — Check engine light with codes 191C02 and 190F08. Rough idle after refueling.
  ❌ Tried (didn't work) Waiting for the code to clear on its own (it would, but then returned).
  ✅ What actually fixed it Replaced the Fuel Tank Breather Valve (PN 13907643106) despite the light being off at the time of repair. The owner reported a noticeable improvement in startup, idle, and throttle response, suggesting the part was failing slowly.
• YouTube Creator Foreign Werks (2019 BMW 330i xDrive (G20, but uses same B46 engine and vent valve as late F30)) — Codes P0446, P0440, 190F08, 191C02.
  ❌ Tried (didn't work) Resetting the codes repeatedly.
  ✅ What actually fixed it Replaced the Fuel Tank Vent Valve (PN 13907643106). Upon dissecting the old valve, it was found to be heavily clogged with carbon buildup, preventing proper operation.
• NHTSA ODI #11697141 — An owner of a related BMW model reported that the vehicle was able to restart only after several attempts, with DTCs P0172 and P0446 retrieved. The failure was related to a manufacturer service bulletin regarding the fuel system.

"I Checked Everything" — The Actual Cause

• In some cases, a P0446 circuit code will not be accompanied by a physical leak that a smoke test can find. If a smoke test passes, the fault is almost certainly electrical, pointing to the vent valve solenoid coil itself, the DMTL pump motor/internal valve, or the wiring to these components. The DME is detecting an incorrect voltage, resistance, or lack of response from the component, not necessarily a system leak.

When the Usual Fixes Don't Work

• A user on the f30.bimmerpost forum reported a case where the dealership replaced the DMTL pump under warranty, but the check engine light returned a week later. A subsequent diagnosis indicated a short circuit or high resistance in the wiring between the DMTL pump and the ECU. This highlights that even when a component is a known failure item, a wiring fault can produce the same code and symptoms, leading to a misdiagnosis if the circuit itself isn't tested.

OEM Part Supersession History

• 13907645860 → 13907643106 — Standard part revision by the manufacturer (Bosch/BMW) for improved reliability or material changes.
  Heads up: The parts are interchangeable; 13907643106 is the correct current replacement.
• 16137315813, 16137448092 → 16137333302 — Standard part revision for the DMTL pump.
  Heads up: The parts are interchangeable; 16137333302 is the correct current replacement for the F30 platform.

Model Year Variations Within This Range

• 2012-2016 (approx.): Primarily equipped with N20/N26/N55 engines. While the EVAP system layout is similar, the N20 engine has known reliability concerns (e.g., timing chain) that are separate from the EVAP system but relevant to overall vehicle health. The B48 is considered more reliable.
• 2016-2019 (approx.): Transitioned to the more modern B46/B58 engines. These engines use a closed-deck block design and have improved reliability over the N20. The common P0446 failure parts, like the tank vent valve (13907643106), are shared with these newer engines, indicating the fault pattern continued across engine generations.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• N20 Engine Timing Chain Guide Failure 🔴 High — Common on models produced before March 2015. Can occur as early as 50,000 miles. Characterized by a high-pitched whining noise from the front of the engine. (Ref: BMW issued an extended warranty in some regions, but no universal recall. The issue stems from defective plastic timing chain guides that can break apart.)
• Electric Water Pump Failure 🔴 High — Common across most modern BMW engines (N20, N55, B46/B58) between 60,000 and 80,000 miles. Failure is often sudden and without warning, leading to rapid overheating. (Ref: No recall, considered a wear-and-tear item. It is highly recommended to replace the thermostat at the same time as the water pump.)
• Oil Filter Housing Gasket Leak 🟠 Medium — Extremely common on N20, N55, and other engines. The gasket becomes hard and brittle, allowing oil (and sometimes coolant) to leak down the side of the engine block. Typically occurs after 60,000 miles. (Ref: No recall. Replacement requires removing the intake manifold on the N20/N26 engines.)

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this repair, using a used part is generally not recommended. Both the Fuel Tank Vent Valve and the DMTL pump are relatively low-cost electronic/mechanical parts that fail due to internal wear, heat cycles, and exposure to the elements. The savings from a used part are minimal compared to the risk of receiving a part that has already endured significant wear and may fail soon after installation.

Donor-vehicle mileage cap: roughly under 40000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a DMTL pump, visually inspect the housing for cracks or signs of moisture intrusion.
• Check electrical connectors on both parts for corrosion or broken pins.
• Ask for the donor vehicle's mileage; a low-mileage donor is always preferable.
• Avoid parts from vehicles in regions with heavy road salt usage, as this accelerates corrosion of under-car components like the DMTL pump.

OEM-only on this vehicle (don't cheap out):

• While not strictly 'OEM-only', using a reputable OEM supplier like Bosch for these parts is highly recommended. The cost difference between a Genuine BMW part and a Bosch equivalent is often significant, yet the quality is identical as Bosch is the original manufacturer.

Aftermarket brands forum-validated for this vehicle:

• Bosch (for both Fuel Tank Vent Valve and DMTL Pump)

Brands owners have reported issues with on this vehicle:

• Unnamed, no-brand parts from online marketplaces should be avoided. While brands like URO Parts exist as a budget alternative, owner feedback is mixed and OEM/OES parts from Bosch offer better-guaranteed longevity for a modest increase in price.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0440 — Often appears alongside P0446 when the fuel tank vent valve fails, as seen in owner reports for the B58 engine.
• P0456 — A small leak code that can be triggered by a faulty gas cap seal, which is a secondary check for P0446 symptoms.
• 191C02 — A BMW-specific manufacturer code identified in TSB SI B13 02 12 as being caused by the same defective fuel tank ventilation valve.

Frequently Asked Questions