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BMW fault codes: B48 engine code guide
The codes stored by the engine control unit on G-series BMWs, what they mean and where to look first.
How BMW fault codes work
BMW’s own fault codes have six digits, for example 120308. The first digits identify the system and the last ones the type of fault. The P-codes shown by generic OBD tools cover only a limited, emissions-related part; the BMW code describes the fault in far more detail and is the same code the dealer sees in ISTA.
The MOSTUNED app reads these BMW codes directly from the engine control unit and shows them with their description. The app’s database defines more than 3,000 codes for the B48 family’s engine control unit. Reading and clearing faults is free.
Most searched B48 fault codes
For B48-engined G-series cars such as the 320i, 420i, 520i and X3 sDrive20i.
| Code | System | Meaning |
|---|---|---|
| 120308 | Boost (charging) pressure control | Charging pressure control: Pressure too low |
| 118001 | Mixture control | Mixture control: Fuel-air mixture too lean |
| 180001 | Catalytic converter efficiency | Catalytic converter: Efficiency too low |
| 140010 | Misfire | Combustion misfires, several cylinders: detected |
| 11A002 | Fuel high pressure | High pressure fuel: Pressure too low |
| 1D2008 | Map thermostat | Map thermostat: jammed open |
| 130713 | VANOS | VANOS solenoid valve, inlet: Position not reached |
| 152108 | Super-knocking | Super-knocking, cylinder 1: Fuel injection deactivation |
| 123401 | Electric wastegate | Electrical wastegate valve, adaptation: Cold start not learned |
Stored versus active codes
Not every entry is a live fault. The engine control unit also keeps faults that occurred once in the past and are not present now. If a code does not return after clearing, it was a passing condition; if it comes straight back, the fault is still there. So the right method is to note the code, clear it and read again under the same conditions.
Read the code yourself, free
- 1 Install MOSTUNED on your iPhone.
- 2 Connect to the car with an ENET cable or WiFi-ENET adapter.
- 3 Open “Fault Codes” under Diagnostics; stored codes are listed with their descriptions.
- 4 Note the code, fix the cause, then clear it from the same screen and read again to confirm.
Frequently asked questions
Can I read BMW fault codes from my phone?
Yes. The MOSTUNED app runs on iPhone, connects to the car with an ENET cable or WiFi-ENET adapter, and reads and clears fault codes for free.
Is clearing fault codes paid?
No. Reading and clearing faults is free; you do not need to buy a package.
Which cars does it work on?
On G-series BMWs with an ENET connection. Engine software packages are ready for the B48B16-engined 320i, 420i, 520i and X3 sDrive20i.
The code I am looking for is not listed.
This page covers the most searched codes; the app recognises many more. Send us the code and your car model on WhatsApp and we will tell you what it means.
Next step
- Download the app — Fault reading and clearing are free
- ENET cable and adapter guide — What you need to connect
- Using the Logger — Narrow down the cause with live data
Contact
Not sure?
Send your model, hardware and goal — we will pick the right package together. We do not sell what does not fit.