BMW 2EAF — NOx Sensor 2 Communication
- Severity
- Informational
- Module
- DME
- OBD-II Code
- U029E, U1145
Description
Fault code 2EAF indicates the DME has lost communication with nitrogen oxide (NOx) sensor 2 (Bank 2). This sensor monitors NOx concentration in the exhaust stream on the second bank of the engine. It serves the same emissions control function as NOx sensor 1 but covers the opposite cylinder bank on V-configuration engines or a downstream position on inline engines with dual NOx sensor configurations.
The DME detected that CAN bus messages from NOx sensor 2 (Bank 2) stopped arriving within the expected timeframe. The fault is set after a communication dropout persists for more than 0.3 seconds with Terminal 15 on and system voltage above 10 V. U029E appears on newer software versions; U1145 on older versions — both indicate the same underlying fault.
2EAF - U029E, U1145: NOx Sensor 2 Communication - Communication loss
Symptoms
No MIL or EML illumination. Reduced engine power is possible as a secondary effect — the DME may limit performance when it cannot verify exhaust emissions on Bank 2. On diesel vehicles with SCR systems, AdBlue/DEF injection for Bank 2 may be affected. OBD readiness monitors related to catalyst or NOx aftertreatment may remain incomplete.
Common Causes
- Failed NOx sensor 2. Internal electronics or ceramic sensing element degradation due to thermal cycling and exhaust contamination. Most common cause.
- Heat-damaged wiring harness. The Bank 2 sensor harness often routes near exhaust components and turbocharger plumbing, making it even more susceptible to heat damage than Bank 1 on some engine configurations.
- Corroded or melted sensor connector. The Bank 2 connector location varies by engine — on some V8 configurations it is in a particularly tight, high-heat area.
- CAN bus fault on the sensor's network segment. Check for concurrent U-codes.
- Power supply fault to the sensor — blown fuse or broken power feed wire.
Diagnosis Steps
- Read all stored fault codes with ISTA. Note whether 2EAE (NOx sensor 1) is also present — both sensors failing simultaneously points to a shared CAN bus or power supply issue rather than individual sensor failure.
- Locate NOx sensor 2 (Bank 2 position). On V-configuration engines, this is typically on the rear exhaust manifold or downpipe. On inline engines with dual NOx sensors, this is the downstream sensor. Inspect the connector and harness for heat damage, melted insulation, or corrosion.
- Check the NOx sensor power supply fuse for Bank 2. Consult the fuse diagram for your chassis.
- Use ISTA to run the NOx sensor system test if available. Confirm whether the sensor responds on the CAN bus.
- If no system test is available, monitor CAN bus traffic for NOx sensor 2 messages. No messages with the sensor connected and powered confirms a sensor or wiring failure.
- Check wiring continuity and for shorts if the sensor itself tests functional. If wiring is intact, replace the NOx sensor. Refer to BMW ETK for the correct part number for your engine and exhaust variant.
Resolution
Replace the failed NOx sensor 2 or repair damaged wiring. The same procedure applies as for NOx sensor 1 — use a specialized NOx sensor socket, apply penetrating lubricant to the threads, and work on a cool exhaust. After replacement, clear fault codes and perform a drive cycle for the DME to re-establish communication. No coding or programming is required.