P2421 on 2010-2016 Mini Countryman: EVAP Vent Valve Stuck Open Causes and Fixes

What's Unique About the 2010-2016 Mini Countryman

On the R60 Countryman, there is significant confusion between two related parts: the 'purge valve' (in the engine bay) and the 'vent valve' (at the rear, near the charcoal canister). While P2421 specifically points to the vent valve circuit, forum discussions and even some mechanic videos show that a failing purge valve can sometimes trigger this code. MINI has also issued extended warranties for the purge valve on many models from this era due to high failure rates, making it a critical first check. The warranty for the fuel tank purge (breather) valve has been extended to 15 years/150,000 miles for many vehicles, an increase from a previous 10-year/120,000-mile extension.

Symptoms You May Notice

• Check Engine Light is on.
• Difficulty starting the engine, especially after getting gas.
🎬 Watch: Why your Mini won't start after refueling.
• A noticeable fuel smell near the rear of the vehicle.
• Vehicle will not pass an emissions test.
• Rough idle, particularly after a cold start or after refueling.
• Slight decrease in fuel economy.

Most Likely Causes

1. Failed EVAP Purge Valve (in Engine Bay) 🔴 High Probability This part is a known high-failure item on this platform, to the point that MINI has offered a 15-year/150,000-mile extended warranty on it for many models due to material and operational issues. It is sometimes referred to as the 'fuel tank breather valve'.
   How to confirm: Listen for a constant clicking noise from the valve. Use a scan tool to command the valve and see if it responds. You can also remove the valve and try to blow through it; if air passes freely when it should be closed, it is stuck open. A failed purge valve can also cause lean mixture codes like 118001 or 118401.
   Typical fix: Replace the purge valve. It is located under the intake manifold in the engine bay. Given the extended warranty, the first step should be to contact a MINI dealer with your VIN.
   Est. part cost: $50-$120
2. Failed EVAP Vent Valve / DMTL Pump Assembly 🟡 Medium Probability The vent valve is integrated with the Leak Detection Pump (DMTL) and is exposed to the elements under the car, making its wiring and the valve itself susceptible to corrosion and failure. The plastic components can become brittle over time.
   How to confirm: Use a bidirectional scan tool to command the vent valve to close; if the system still cannot hold pressure (verified with a smoke test), the valve is likely stuck open. Inspect the wiring and connector for corrosion or damage. A user on North American Motoring with a 2012 Countryman S All4 reported a code 3225 (DMTL short at pin B+) which pointed directly to a failed pump.
   Typical fix: Replace the DMTL pump assembly, which includes the vent valve. This is located near the charcoal canister, accessible by removing the driver's side rear wheel and fender liner, or sometimes by just lowering a plastic skid plate in front of the rear wheel.
   Est. part cost: $100-$200
3. Damaged or Corroded Wiring ⚪ Low Probability Wiring for the rear-mounted DMTL pump/vent valve is exposed to road salt and moisture, which can lead to corrosion or breaks in the circuit over time.
   How to confirm: Visually inspect the harness leading to the DMTL pump. Use a multimeter to check for continuity and proper voltage at the connector when the valve is commanded by a scan tool.
   Typical fix: Repair the damaged section of the wiring harness and protect it from the elements. In some cases, the connector pigtail may need to be replaced.
   Est. part cost: $5-$20

Rare But Worth Checking

• Cracked Charcoal Canister: Overfilling the fuel tank by continuing to pump after the nozzle clicks off can saturate the charcoal canister with liquid fuel, causing it to crack or fail, which can lead to various EVAP codes.
• Loose or Faulty Gas Cap: While a bad gas cap usually triggers a 'small leak' or 'gross leak' code (like P0456 or P0455), it's a simple and cheap item to check or replace before moving to more complex diagnostics. A user on North American Motoring reported resolving a P2421 code simply by cleaning the gas cap seal.

Diagnosis Steps

1. Call a MINI dealership with your VIN. Inquire about the extended warranty for the 'fuel tank purge valve' or 'breather valve' (TSB SI M01 01 24). This may entitle you to a free replacement.
2. Inspect the gas cap. Ensure it is tightened until it clicks and that the rubber seal is not cracked or brittle. Clean the seal and the filler neck surface.
3. Locate the purge valve in the engine bay (under the intake manifold). Listen for excessive clicking. With the engine off, disconnect it and see if you can blow through it. If air passes, it's stuck open and needs replacement.
4. If the purge valve is okay, locate the DMTL pump/vent valve assembly. It's behind the driver's side rear wheel well liner, often visible by looking in front of the rear wheel.
5. Inspect the wiring and connector going to the DMTL pump for any signs of green corrosion, chafing, or breaks.
6. If a bidirectional scan tool is available, command the vent valve to close. Perform a smoke test on the EVAP system. If smoke exits from the vent valve/DMTL pump area, the valve is stuck open and the DMTL pump assembly needs to be replaced.
7. If no smoke is present but the code persists, the issue may be an internal failure of the DMTL pump's sensor or a more complex wiring issue that requires multimeter testing for voltage and ground at the connector.

Parts You'll Likely Need

• Fuel Tank Purge Valve (OEM #13907618647) — This is the most common failure point in the Mini EVAP system for this generation and is often covered by a 15-year/150,000-mile extended warranty. It's located in the engine bay.
  Trusted brands: Bosch, Delphi, Genuine BMW/Mini
  OEM price range: $90-$130
  Aftermarket price range: $40-$80
• EVAP Leak Detection Pump (DMTL) (OEM #16137193479) — This assembly, located at the rear of the car, contains the vent valve that the P2421 code directly references. It is replaced if the valve is confirmed to be stuck open.
  Trusted brands: Bosch, Genuine BMW/Mini
  OEM price range: $150-$220
  Aftermarket price range: $100-$160

Related Codes That Often Appear With This One

• P0455 — A 'Gross Leak Detected' code can appear alongside P2421 because a vent valve that is stuck wide open is considered a very large leak by the system.
• P0442 — A 'Small Leak Detected' code can sometimes accompany P2421 if there are multiple issues or if the system's interpretation of the fault is intermittent.
• 190F08 — A manufacturer-specific code for 'fuel tank ventilation system: malfunction', which can be triggered by a faulty purge valve.

Technical Service Bulletins (TSBs) & Recalls

• M010424: Announcing an extended warranty for the EVAP purge (vent) valve to 10 years/120,000 miles. [This has since been updated].
• SI M01 01 24: Updates the extended limited warranty for the fuel tank purge (breather) valve to 15 years/150,000 miles for eligible vehicles. This TSB also notes that related fault codes like 190F08 can point to a faulty valve.
• SI M01 01 19: An earlier TSB extending the fuel tank vent valve warranty to 10 years/120,000 miles, which also applies to PZEV/SULEV vehicles for 15 years/150,000 miles.

Platform-Specific Known Issues

• Purge Valve vs. Vent Valve Confusion: Owners and even mechanics frequently confuse the engine bay-mounted purge valve with the rear-mounted vent valve (part of the DMTL pump). P2421 technically refers to the rear vent valve, but the front purge valve is a far more common failure and can sometimes trigger this code. The existence of a major extended warranty on the purge valve makes it the primary suspect regardless of the specific code.
• Real Repair Story: DMTL Pump Replacement: A user on the North American Motoring forum with a 2012 Countryman S ALL4 experienced a check engine light with code 3225 (a manufacturer-specific code for 'DMTL short at pin B+'). They successfully resolved the issue by replacing the DMTL pump themselves. The repair was described as relatively easy, involving jacking up the car, removing 4 nuts on a plastic skid plate, and 3 Torx screws on the pump itself, without needing to remove the wheel.

Mechanic-Grade Diagnostic Values

• EVAP Purge Valve (Breather Valve) Coil Resistance — expected: 15-30 Ohms. Failure: A reading of 0 Ohms (short circuit) or infinite/OL (open circuit).
• DME 5-Volt Reference Circuit — expected: 4.97V - 5.01V. Failure: A voltage reading significantly higher than 5.0V (e.g., 5.2V or more) can indicate an internal fault in the DME, while a low or zero voltage reading suggests a short or open in the wiring or a connected sensor.
• DMTL Pump Operation — expected: The DME monitors the amperage (current) draw of the pump motor as it pressurizes the system against a known orifice size (e.g., 0.5mm).. Failure: The system detects a leak if the amperage draw does not match the expected value for a sealed system. Specific amperage values are not published, as this is an internal calculation by the DME.

Hidden / Shadow Codes Worth Checking

• 3225: DMTL short at pin B+. This is a highly specific code pointing directly to an electrical fault within the DMTL pump assembly. (see via Professional-level scanners like Autel or a BMW-specific tool like ISTA.)
• 190F08: Tank ventilation system: Malfunction. This is a common BMW/Mini code that frequently points to a failed purge valve (breather valve) in the engine bay. (see via BMW-specific scanners like ISTA or capable tools like BimmerLink.)
• 272A: DMTL solenoid valve. This indicates a fault with the changeover valve inside the DMTL pump assembly. (see via Professional-level scanners.)
• 272E: DMTL pump motor. This points to a failure of the electric motor within the DMTL pump. (see via Professional-level scanners.)
• 1447: Leakage Diagnostic Pump Reed Switch Did Not Open. This code points to a failure within the DMTL pump assembly. (see via Professional-level scanners.)

Scan Tool Commands That Help

• ISTA (Rheingold/ISTA-D): DMTL Pump Activation / Diagnose Module for Tank Leaks — This is the primary diagnostic function to test the entire EVAP system as the DME would. It commands the DMTL pump to run through its full test cycle: a reference measurement, a major leak test, and a minor leak test. This can help confirm if the pump is working and if the system can seal, potentially identifying a leak source like a bad gas cap seal while the test is running.
• ISTA (Rheingold/ISTA-D): Reset DME Adaptation Values — This should be performed after replacing any major EVAP system component like the purge valve or DMTL pump. Resetting adaptations forces the DME to relearn the operational parameters of the new components, which can be critical for resolving persistent codes, especially the 190F08 fault.

Wiring & Ground Locations

• DMTL Pump Harness Chafe Point — The wiring harness leading to the DMTL pump, located in the driver's side rear wheel well area, has been found to be improperly secured to the rear swing arm on some vehicles.. The constant movement of the suspension can cause the harness to rub against the chassis or swing arm, eventually wearing through the insulation and causing wires to corrode and break. This creates an open circuit, which can trigger P2421 and related DMTL codes like P2418 and P2400. The fix is to repair the broken wires and re-route the harness so it is secured to the body, not the moving suspension components.
• Fuse F05 — In the under-hood fuse box (also called the front power distribution box).. Fuse F05 supplies power to the 'tank leakage diagnose pump' (DMTL). If this fuse is blown, the pump will have no power, leading to a fault code.
• DME Connectors — The main engine computer (DME) has several large multi-pin connectors, often designated with 'X' numbers like X60004, X60211, and X60212.. These connectors are the source of the command signals and power for the entire EVAP system. A poor connection or corrosion at one of these pins could cause a fault. Advanced diagnosis may require checking for signals at these connectors.

Real Owner Repair Stories

• North American Motoring forum user 'contrail' (2012 Mini Countryman S ALL4) — Check Engine Light with manufacturer code 3225 'dmtl short at pin B+'
  ✅ What actually fixed it Replacing the DMTL pump assembly. The user noted the repair was relatively easy and could be done without removing the rear wheel by lowering a plastic skid plate.
• YouTube channel 'kansascitytdi' (2010 Mini Cooper (R56, but same principle applies to R60)) — Check Engine Light with codes P2418 (EVAP Switching Valve Control Circuit Open) and P2400 (EVAP LDP Control Circuit Open).
  ❌ Tried (didn't work) Checking fuse F05, which was found to be good.
  ✅ What actually fixed it Found broken wires in the DMTL pump harness where it was incorrectly routed and secured to the moving rear swing arm. The wires were repaired and the harness was re-routed to prevent future damage, which resolved the codes.
• North American Motoring forum user 'MINI Duke' (Mini Cooper S (model year not specified, but in R60 context)) — P2421 code and hesitation when starting after refueling.
  ✅ What actually fixed it Replacing the 'fuel tank rebreather valve' (the purge valve located in the engine bay).
• Bimmerpost forum user 'dmaxdmax' (BMW X3 F25 with N20 engine (different vehicle, but same EVAP system principles and codes)) — Persistent code 190F08 after multiple attempted fixes.
  ❌ Tried (didn't work) Replacing the purge valve (both used OEM and new OEM)., Replacing the DMTL pump., Performing multiple smoke tests, which found no leaks.
  ✅ What actually fixed it Discovered that the electrical connectors for two different differential pressure sensors near the throttle body had been swapped. The connectors were physically identical. After swapping the connectors back to their correct positions and resetting the DME adaptation values with ISTA, the fault was resolved.

"I Checked Everything" — The Actual Cause

• In a well-documented case on a BMW with a persistent 190F08 code (often seen with Mini EVAP issues), multiple smoke tests showed no leaks. The owner replaced both the purge valve and the DMTL pump to no avail. The actual root cause was found to be two physically identical sensor connectors near the throttle body that had been swapped by a previous workshop. Correcting the wiring and resetting DME adaptations finally fixed the problem, highlighting that electrical faults can mimic leaks and will not be found by a smoke test.

OEM Part Supersession History

• 16136764191, 16136752551 → 16137193479 — Component revision and consolidation.
• 13907572236 → 13907618647 — Component revision for the fuel tank purge/breather valve.

Model Year Variations Within This Range

• 2010-2016: The R60 Countryman was available with the naturally-aspirated N16 engine (Base models) and the turbocharged N18 engine (S and JCW models, from 2011). While the N18 is a more complex engine with direct injection and a turbo, the fundamental EVAP system components (DMTL pump, purge valve, canister) and their common failure modes for this code are largely the same across both engine types for this generation.

Diagnostic Flowchart

Other Known Issues on This Vehicle

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

• Timing Chain Failure ('Death Rattle') 🔴 High — Common on N14 and to a lesser extent N18 engines. Can occur from 60,000 miles onward. Caused by stretching chains, failing tensioners, and broken plastic guides.
• High-Pressure Fuel Pump (HPFP) Failure 🔴 High — Very common, especially on earlier N14/N18 engines (pre-2012). Symptoms include long cranks, rough cold starts, and low power/limp mode. An extended warranty was offered on some models. (Ref: Yes, extended warranty programs were issued for certain model years.)
• Plastic Thermostat Housing Leak 🟠 Medium — The plastic housing is prone to cracking and leaking coolant, often after 50,000-80,000 miles. This can lead to overheating if not addressed.
• Excessive Oil Consumption 🟠 Medium — Particularly prevalent in the turbocharged N14 and N18 engines. Caused by issues with piston rings, valve stem seals, or the PCV system integrated into the valve cover.
• Water Pump & Crossover Pipe Failure 🟠 Medium — The water pump can fail, and the plastic coolant crossover pipe that connects it to the thermostat housing often becomes brittle and breaks during thermostat replacement, or on its own.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For purely mechanical, non-electronic components like the charcoal canister itself, a used part from a reputable auto recycler can be a cost-effective option, provided it is inspected for cracks. For electronic items like the DMTL pump or purge valve, buying used is a significant gamble, as their failure is often electronic or due to internal wear not visible externally.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a charcoal canister, ensure there are no visible cracks in the plastic housing.
• Check that none of the plastic hose nipples are broken or brittle.
• Avoid any parts that show signs of being saturated with liquid fuel.
• For any used part, try to source from a vehicle with the lowest possible mileage and from a dry climate to minimize corrosion.

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

• DMTL Pump (Vent Valve Assembly)
• Purge Valve (Fuel Tank Breather Valve)

Aftermarket brands forum-validated for this vehicle:

• Bosch: Bosch is the Original Equipment Manufacturer (OEM) for the DMTL pump and other fuel system components on this vehicle. Buying a Bosch-branded part is equivalent to getting a Genuine Mini part without the dealership markup.

Brands owners have reported issues with on this vehicle:

• Unbranded/No-Name Parts: Forum users and repair professionals strongly advise against using cheap, unbranded electronic parts from online marketplaces. While the initial cost is low, they have a high failure rate, often leading to the code returning quickly and requiring the job to be done a second time.

Real Owner Stories

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

Related OBD-II Codes

• 118001 — A manufacturer-specific lean mixture code. Can be triggered by a failed EVAP purge valve stuck open, which creates a vacuum leak and is a common root cause for EVAP system faults on this vehicle.
• 118401 — A manufacturer-specific lean mixture code, similar to 118001. It often appears when the EVAP purge valve fails in the open position, a common issue that can be associated with P2421.
• 3225 — A manufacturer-specific code for 'DMTL short at pin B+'. This code points directly to an electrical failure within the DMTL pump/vent valve assembly, which is the component P2421 is designed to monitor.
• 190F08 — A manufacturer-specific fault code mentioned in MINI TSB SI M01 01 24 as being related to a faulty fuel tank purge (breather) valve, a primary suspect when diagnosing any EVAP code on this platform.

Frequently Asked Questions