P0D99 flags a general electrical fault in temperature sensor A of the charging inlet, the element that tells the car how hot the power contacts are. At high current, contact resistance heats the pins; the reading lets the car throttle or stop charging (TE Connectivity, US10960781B2). Inlet suppliers fit resistive sensors: Phoenix Contact strings PTC elements along the AC pins and puts a Pt 1000 on each DC pin, with shutdown above +90 °C at the contact. For the third-generation smart electric drive with 22 kW charger, Mercedes defines P0D9900 as an electrical fault of the inlet contact temperature sensor; bulletin LI54.10-P-067823 traces it, like neighbouring sensor codes, to loose low-voltage plugs at the charger. Without a usable reading, charging is refused or limited. Implausible, low and high readings are P0D9A–P0D9C.
High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.
Symptoms
- High-voltage battery cannot be charged
- Charging only at reduced power
- Charging system fault message
Most likely causes
- Loose low-voltage connector at the on-board charger (smart)
- Damaged sensor wiring between inlet and charger
- Temperature element in the inlet failed (usually replaced with the inlet harness)
- Evaluation input in the charger module defective
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
What each character of P0D99 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- D: Subsystem depends on the code range
- 99: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0D99?
If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.
What causes code P0D99?
The most common causes are: loose low-voltage connector at the on-board charger (smart); damaged sensor wiring between inlet and charger; temperature element in the inlet failed (usually replaced with the inlet harness).
Related codes
- P0D9ABattery Charger Coupler Temperature Sensor A Circuit Range/Performance
- P0D9BBattery Charger Coupler Temperature Sensor A Circuit Low
- P0D9CBattery Charger Coupler Temperature Sensor A Circuit High
- P0D9DBattery Charger Coupler Temperature Sensor A Circuit Intermittent/Erratic
- P0E5FBattery Charger Coupler Temperature A Too High
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.