1. What is P2401 in Mercedes C300 L?

The P2401 OBD-II code stands for Evaporative Emission (EVAP) System Leak Detection Pump Control Circuit Malfunction. For the Mercedes-Benz C-Class W206 C300 L (2022-2024)—a top-selling luxury sedan with high market demand—it targets the EVAP leak detection pump (LDP) in its M254 2.0T mild-hybrid engine, standard in Luxury, AMG Line, and Exclusive trims (paired with 9-speed 9G-TRONIC transmission).

The C300 L’s EVAP system captures fuel vapors from the gas tank and routes them to the engine for combustion. The leak detection pump (LDP) pressurizes the EVAP system to detect leaks (0.5–1.0 psi) during key-off or idle conditions. Controlled by a 12V signal from the ECU, the pump’s control circuit includes wiring, a relay, and the pump motor. P2401 triggers when the ECU detects abnormal voltage (≤0.5V or ≥13V) or no current flow in the LDP control circuit—indicating a malfunction that prevents proper leak detection.

Mercedes C300 L Specific Note: This code is widespread in 2022-2023 C300 L AMG Line models, per Mercedes Technical Service Bulletin (TSB) 23-05-12. The M254’s leak detection pump (#A0004708594) uses a plastic housing that cracks in high-humidity environments—moisture seeps into the control circuit, causing short circuits or signal drops that trigger P2401 Mercedes EVAP control circuit faults. The TSB recommends replacing the faulty pump with an updated aluminum-housing version (#A0004709294) to prevent recurrence.

2. Common Causes of P2401 in 2022-2024 C300 L

P2401 in Mercedes C300 L M254 models stems from EVAP leak detection pump control circuit malfunctions—below are real-world cases diagnosed with the ICARZONE UR800:

• Leak Detection Pump Failure (2023 C300 L AMG Line): An owner with 42,000 miles reported a persistent "Check Engine" light. The UR800’s EVAP Pump Control Circuit Test showed 0.3V (normal: 0.8–12V). Inspection revealed a cracked pump housing (TSB 23-05-12 eligible). Replacing the pump with OEM #A0004709294 fixed P2041—common for P2401 Mercedes C300 L 2023 models.
• Wiring Short Circuit (2022 C300 L Luxury): A Luxury trim owner’s P2401 reappeared after heavy rain. The UR800’s Circuit Continuity Test detected a short (14V constant). Tracing the wiring revealed water damage near the rear wheel well—repairing the shorted section resolved the control circuit malfunction.
• Relay Failure (2024 C300 L Exclusive): A 2024 C300 L owner’s P2401 triggered during cold starts. The UR800’s EVAP Relay Test showed no voltage output. Replacing the EVAP pump relay (#A0005457719) restored circuit functionality—relevant for P2401 C300 L cold weather cases.
• ECU Signal Fault (2022 C300 L Premium): A Premium trim owner’s P2401 occurred after a software update. The UR800’s ECU Output Test showed irregular voltage signals to the pump. Updating the ECU firmware via UR800 fixed the signal processing issue—common for P2401 Mercedes software-related faults.

3. Key Symptoms of P2401 in M254 Engine

P2401 symptoms in the Mercedes C300 L focus on EVAP system malfunction and dashboard warnings—watch for these signs of P2401 leak detection circuit issues:

4. C-Class Trims/Engines Prone to P2401

Mercedes service data highlights these 2022-2024 C-Class configurations with the highest P2401 occurrence rates (all M254 engines):

5. Diagnose P2401 with ICARZONE UR800

Diagnose P2401 in your Mercedes C300 L M254 accurately with the UR800’s Mercedes-specific EVAP system tools. Follow these steps (engine off, key in "ON" position; battery voltage 12.4–12.7V):

Case Example: A 2023 C300 L AMG Line failed Step 2 (0.4V) and Step 5 (TSB 23-05-12 eligible). The UR800’s Component Location Tool guided pump access (rear of the vehicle, near the fuel tank). Inspection revealed a cracked pump housing—replacing it with the updated OEM #A0004709294 restored voltage to 11.7V—P2401 cleared, and fuel odor disappeared.

6. How to Fix P2401 in Mercedes C300 L

Resolve P2401 in your C300 L with these UR800-verified solutions—tailored to the M254 engine’s EVAP leak detection system:

1. Replace Leak Detection Pump (Most Common Fix for TSB 23-05-12)

1. Confirm pump failure via UR800’s Step 2 and 5. Raise the vehicle on a jack stand (secure with jack stands) and locate the rear fuel tank area.
2. Locate the leak detection pump: Mounted to the rear subframe, near the fuel tank, with a 2-pin electrical connector and EVAP hose.
3. Disconnect the electrical connector (press the release tab) and pull off the EVAP hose. Remove the pump (2 10mm bolts) with a socket wrench.
4. Install the updated OEM leak detection pump:
   • 2022-2023 C300 L: #A0004709294 (aluminum housing, TSB-compliant)
   • 2024 C300 L: #A0004709594 (factory-updated version)
   Secure the pump with bolts (torque to 8 ft-lbs).
5. Reattach the EVAP hose and electrical connector. Lower the vehicle. Use UR800 to retest voltage (0.8–12V). Clear P2401 and test refueling—confirm no premature pump clicks.

2. Repair Wiring Short Circuit (for Electrical Damage)

1. Confirm wiring damage via UR800’s Step 3. Trace the LDP control wiring from the pump to the ECU (rear of the vehicle, along the frame rail). Look for fraying, corrosion, or water damage.
2. Cut the damaged wire section (use wire cutters) and strip 1/4 inch of insulation from both ends. Splice with heat-shrink butt connectors (#Dorman 84715) rated for automotive use.
3. Crimp the connectors with a wire crimper, then apply heat to seal (ensure no exposed copper). Wrap the repaired section with water-resistant electrical tape.
4. Secure the wiring to the frame rail with zip ties—prevents contact with moisture and moving parts. Reconnect the pump connector.
5. Use UR800 to retest continuity (<1Ω). Clear P2401 and test drive in wet conditions—verify no code reappearance.

3. Replace EVAP Pump Relay (for Relay Failure)

1. Confirm relay failure via UR800’s Step 4. Locate the EVAP pump relay: In the rear fuse box (trunk, right side) — refer to the C300 L’s fuse box diagram (labeled "K17").
2. Remove the rear fuse box cover (press the release tabs). Pull out the EVAP pump relay (use needle-nose pliers if needed).
3. Install an OEM EVAP pump relay: #A0005457719. Ensure the relay is fully seated in the socket.
4. Reattach the fuse box cover. Use UR800 to retest relay output (12V when activated).
5. Clear P2401 with UR800 and test cold starts—confirm smooth EVAP system activation and no warning messages.

7. P2401 Repair Costs & Maintenance Tips

P2401 repair costs for the Mercedes C300 L M254 vary by cause. Use this table to budget for P2401 C300 L repair cost planning:

Maintenance Tips for C300 L Owners

• C300 L AMG Line (2022-2023): Replace the leak detection pump with TSB-compliant #A0004709294 every 50,000 miles (preventive) — avoids housing cracks and P2401 recurrence.
• Luxury trim owners (wet climates): Inspect LDP control wiring every 15,000 miles—repair fraying or corrosion immediately to prevent short circuits and P2401 Mercedes water damage faults.
• Clean the EVAP pump connector with dielectric grease every 30,000 miles—repels moisture and ensures stable electrical contact, critical for P2401 prevention.
• Avoid overfilling the gas tank (stop at first click) — excess fuel can saturate the EVAP canister, increasing strain on the leak detection pump in C300 L models.
• Perform the UR800’s EVAP System Health Check every 20,000 miles — monitor pump voltage and circuit continuity to catch issues before P2041 triggers. Key for P2401 early detection.

8. C300 L-Specific FAQs