Experiencing a frustrating “No Communication” error when trying to read diagnostic codes from your 2007 BMW 328i Coupe using an OBD2 scanner? This issue can prevent you from diagnosing engine problems and passing emissions tests. This guide provides a step-by-step approach to troubleshoot the OBD2 communication error in your BMW E90 328i Coupe.
Initial Scan Tool Check
Before diving into complex diagnostics, start with the basics. Use a generic OBD2 scan tool to attempt communication with the Engine Control Unit (ECU), also known as the DME in BMW terminology. A simple scan tool, available at most auto parts stores, can quickly determine if the issue is a basic connectivity problem.
“I have one of those ELM327 and it connects and shows RPM when I start it but the software I have isn’t that sophisticated.”
If your scan tool, like an ELM327, establishes a partial connection (showing RPM) but fails to retrieve codes, it indicates a potential issue beyond a simple lack of power to the OBD2 port.
Power and Ground Verification at OBD2 Port
A functional OBD2 port requires proper power and ground. Check the following at your OBD2 socket (X19527):
- Pin 16: Should have 12V+ power at all times. This is a direct battery feed.
- Pin 4 & 5: Ground pins. Verify a good ground connection.
- Pin 1: Should have 12V+ power when the ignition is switched ON. This is ignition-switched power.
“Both Check OKAY”
If you confirm power and ground at the OBD2 port, the problem likely resides in the communication lines, specifically the D-CAN (Diagnostic CAN) line.
D-CAN Line and JBE Connector Inspection
The D-CAN line is crucial for data transmission between the OBD2 port and the vehicle’s communication network. In BMW E90 models, the D-CAN line from the OBD2 socket connects to the Junction Box Electronics (JBE), also known as the JB Fuse Panel.
Locate connector X14271 at the JBE. This connector houses the D-CAN line. Inspect the connector and its pins for any signs of corrosion, damage, or loose connections. Pay particular attention to Pin #33 of connector X14271. This pin is where the D-CAN line from Pin #7 of the OBD2 socket (X19527) terminates and connects to the vehicle’s bus system within the JBE.
“It is the blue connector (towards left or drivers side) and yes there is continuity between #7 and #33”
If continuity between OBD2 socket Pin #7 and JBE connector X14271 Pin #33 is confirmed, the physical D-CAN line is likely intact. However, issues within the JBE or related modules could still be the cause of the communication error.
JBE Connector X14271 Location Variation
It’s important to note that the location of connector X14271 on the JBE can vary depending on the production date of your 2007 BMW 328i Coupe. BMW revised the JB Fuse Panel layout around March 1, 2007.
For 2007 BMW 328i Coupe manufactured BEFORE 03/01/2007: Connector X14271 is typically located on the inboard side of the JBE.
For 2007 BMW 328i Coupe manufactured AFTER 03/01/2007: Connector X14271 is generally found on the outboard side of the JBE.
Refer to these diagrams to identify the correct location of connector X14271 in your vehicle based on its production date and JB Fuse Panel configuration.
Regardless of the JBE variant (JBBF 70 or JBBF 87), the pinout configuration of connector X14271 remains consistent.
Conclusion
Troubleshooting a “No Communication” OBD2 error on a 2007 BMW 328i Coupe requires a systematic approach. By verifying power and ground at the OBD2 port, inspecting the D-CAN line and JBE connector X14271, you can isolate potential issues. If all checks pass, the problem may lie deeper within the vehicle’s communication network or the DME itself, requiring further professional diagnostics. Remember to always consult BMW technical documentation (TIS) for accurate wiring diagrams and component locations specific to your vehicle’s production date.
