1. What is P0444 in Mercedes GLC 300 L?

The P0444 OBD-II code stands for EVAP System Purge Solenoid Circuit Open. For the Mercedes-Benz GLC 300 L (2019-2024)—a top-selling European luxury SUV—this code targets the EVAP purge solenoid in its 2.0T M264 engine, standard in GLC 300 L 4MATIC, AMG GLC 43, and GLC 300 L Luxury trims (paired with 9-speed 9G-TRONIC transmission).

The GLC 300 L’s EVAP system captures fuel vapors from the tank and routes them to the engine via the purge solenoid. The solenoid opens/closes (controlled by the ECU) to "purge" vapors during driving—reducing emissions. P0444 triggers when the ECU detects no current flow in the solenoid circuit (resistance >100Ω or voltage <9V)—indicating a faulty solenoid, broken wiring, or loose connectors.

Mercedes GLC 300 L Specific Note: This code is widespread in 2020-2023 GLC 300 L 4MATIC models, per Mercedes Technical Service Bulletin (TSB) 21-08-03. The M264’s compact engine bay routes the solenoid harness near the exhaust; heat and vibration cause wire insulation to crack, leading to open circuits.

2. Common Causes of P0444 in 2019-2024 GLC 300 L

P0444 in Mercedes GLC 300 L M264 models stems from EVAP purge solenoid circuit failures—below are real-world cases diagnosed with the ICARZONE UR800:

• Faulty Purge Solenoid (2021 GLC 300 L 4MATIC): An owner with 61,000 miles reported a "Check Engine" light and fuel odor. The UR800’s EVAP Solenoid Test showed resistance 150Ω (normal: 15–30Ω). Replacing the solenoid with OEM #A0001405466 (per TSB 21-08-03) fixed P0444.
• Broken Solenoid Wiring (2020 GLC 300 L Luxury): A Luxury trim owner’s P0444 reappeared after solenoid replacement. The UR800’s Circuit Continuity Test found a broken wire—insulation melted by exhaust heat (harness runs along the front of the catalytic converter). Repairing with heat-resistant wire (#Dorman 10501) restored current flow.
• Loose Connector (2019 AMG GLC 43): An AMG owner’s P0444 occurred after off-road driving. The UR800’s Connector Resistance Test showed 80Ω (normal: <1Ω) at the solenoid plug. Re-seating the connector and applying dielectric grease fixed the open circuit.
• ECU Driver Failure (2022 GLC 300 L 4MATIC): A 4MATIC owner’s P0444 persisted after wiring repairs. The UR800’s ECU Output Test showed no voltage to the solenoid. Reflashing the ECU with Mercedes firmware v5.1.2 via UR800 resolved the driver issue.

3. Key Symptoms of P0444 in GLC 300 L M264

P0444 symptoms in the Mercedes GLC 300 L focus on EVAP system performance and emissions—watch for these signs that signal circuit issues:

4. Mercedes GLC 300 L Trims/Engines Prone to P0444

Mercedes service data highlights these 2019-2024 GLC 300 L configurations with the highest P0444 occurrence rates (all M264/M177 engines):

5. Diagnose P0444 with ICARZONE UR800

Diagnose P0444 in your Mercedes GLC 300 L M264 accurately with the UR800’s Mercedes-specific EVAP tools. Follow these steps (engine off, key in "ON" position; ensure fuel tank is 1/4–3/4 full):

Case Example: A 2021 GLC 300 L 4MATIC failed Step 2 (145Ω) and Step 5 (TSB 21-08-03 eligible). The UR800’s Component Location Tool guided solenoid access (front of the EVAP canister, near the battery). Replacing the solenoid fixed P0444—verified by test drive (no fuel odor, restored MPG).

6. How to Fix P0444 in Mercedes GLC 300 L

Resolve P0444 in your GLC 300 L with these UR800-verified solutions—tailored to the M264 engine’s EVAP system:

1. Replace EVAP Purge Solenoid (Most Common Fix for TSB 21-08-03)

1. Confirm solenoid fault via UR800’s Step 2. Locate the purge solenoid: Front of the EVAP canister (driver’s side, near the battery), mounted to the frame rail (2-pin connector, 2 Torx screws).
2. Disconnect the solenoid’s electrical connector (press the release tab) and remove the two Torx screws (T25 bit).
3. Pull the old solenoid straight out—inspect the inlet/outlet hoses for cracks (replace if damaged).
4. Install an OEM purge solenoid:
   • 2019-2021 GLC 300 L: #A0001405466
   • 2022-2024 GLC 300 L: #A0001406266 (heat-resistant coil upgrade)
   Reattach the hoses (secure with zip ties if loose).
5. Reinstall the Torx screws (torque to 7 ft-lbs), reconnect the connector. Clear P0444 with UR800 and run a EVAP System Test to confirm no circuit errors.

2. Repair Damaged Solenoid Wiring

1. Confirm wiring issue via UR800’s Step 3. Trace the solenoid harness from the connector to the ECU (runs along the front of the exhaust manifold).
2. Identify melted or frayed insulation—cut out 1 inch of damaged section (use wire cutters) and strip 1/4 inch of insulation from both ends.
3. Splice new 18-gauge heat-resistant wire (#Dorman 10501) using heat-shrink butt connectors. Crimp connectors and apply heat to seal (no exposed wire).
4. Wrap the repaired harness in heat-resistant tape (#3M 33+) to protect against exhaust heat. Secure it to the frame rail with zip ties (avoid hot components).
5. Retest continuity with UR800 (Step 3) and clear P0444. Test drive to confirm no fuel odor or circuit faults.

3. Update ECU Firmware (for Driver Failure)

1. Confirm ECU issue via UR800’s Step 4. Connect UR800 to the GLC 300 L’s OBD-II port (under steering wheel) and turn key to "ON."
2. Select "Mercedes-Benz" > "GLC 300 L" > "M264 2.0T" > "ECU" > "Firmware Update." The tool will detect the current version and download the latest (v5.1.2 for 2022+ models).
3. Do not turn off the key or disconnect UR800 during the update (takes 20–25 minutes). The tool will alert you when complete (ECU reboots automatically).
4. Run UR800’s Step 4 (solenoid activation test) to confirm "click" and 11–14V. Clear P0444 and verify EVAP system functionality with a short test drive.

7. P0444 Repair Costs & Maintenance Tips

P0444 repair costs for the Mercedes GLC 300 L M264 vary by cause. Use this table to budget:

Maintenance Tips for Mercedes GLC 300 L Owners

• GLC 300 L 4MATIC (urban drivers): Replace the purge solenoid every 70,000 miles (preventive) — use OEM #A0001406266 for 2022+ models to avoid TSB 21-08-03 heat damage.
• Inspect the solenoid harness during oil changes—wrap exposed sections with heat-resistant tape (#3M 33+) to protect against exhaust heat (critical for 4MATIC trims).
• Avoid topping off the fuel tank (stop at first click) — overfilling floods the EVAP canister, increasing solenoid load and circuit strain.
• Clean the solenoid connector annually with electrical contact cleaner—apply dielectric grease to prevent corrosion (key for AMG GLC 43 in wet climates).
• Perform the UR800’s EVAP System Health Check every 15,000 miles — monitor solenoid resistance and circuit continuity to catch issues before P0444 triggers.

8. Mercedes GLC 300 L-Specific FAQs