Error code P052F00 means the power supply to the glow plug control unit has malfunctioned. Common symptoms include long cranking during cold starts, warning lights on the dashboard, or inconsistent pre-heating behavior. This article explains what it means, how to locate the control module, and how to fix it yourself.
Watch the full repair guide below:
Understanding Code P052F00
The code P052F00 refers to a malfunction in the glow time control unit’s power circuit. On Mercedes diesel engines, this module manages voltage supplied to glow plugs during cold starts. If the ECU detects an open circuit, short, or improper voltage, it logs this DTC and triggers the engine management or glow coil light.
Common Symptoms
- Hard starting or extended cranking, especially in cold weather
- Glow plug light staying on longer than normal
- Check engine light or coil symbol illuminated
- Possible “Start error” message on dashboard
DIY Diagnostic & Fix
- Locate the glow plug control module: On most 2.1 L diesel engines, it’s positioned near the air filter box — easily accessible once the box is removed.
- Inspect wiring: Ensure all connectors are tight and free of corrosion. Verify 12 V supply at the power input pin.
- Check ground: A weak ground can trigger the same fault.
- Replace module if faulty: If power and ground are present but the fault persists, replace the control unit with an OEM part. Avoid cheap aftermarket modules as they can fail prematurely.
- Scan & clear codes: Use a professional diagnostic tool like the iCarsoft CR ULTRA P to clear stored DTCs and confirm the repair.
Recommended Tool
The iCarsoft CR ULTRA P supports Mercedes-Benz full-system diagnostics, reads and clears all engine and glow plug-related codes, and performs service resets — perfect for DIY technicians.
Quick Tips
- Always disconnect the battery before replacing the glow plug control unit.
- Check fuse and relay associated with the glow system.
- After repair, perform a cold-start test to confirm smooth ignition.
Related Articles & Resources
Read more on similar Mercedes fault codes in our guide for Mercedes P011800 – Coolant Temperature Sensor 1 Short Circuit.
For further technical reading, see OBD-Codes.com P052F and DiagnosticTroubleCodes.com P052F.
FAQ
Q: What causes P052F00 in Mercedes diesel engines?
A: Usually a failed glow plug control module or corroded power/ground wiring. Less often, a blown fuse or relay fault.
Q: Can I drive with this fault code?
A: The engine may still run once warm, but cold starts will be difficult. It’s best to repair promptly to avoid excessive battery drain or start failures.
Q: Do I need to reprogram the new glow plug module?
A: No programming is typically required; just install, reconnect, and clear codes using a scanner.
Q: Will a universal glow plug relay work?
A: No — use a genuine or OEM-spec Mercedes module for reliable operation and correct voltage timing.
