Experiencing a “No Communication” error when trying to connect your OBD2 scan tool to your 2007 BMW 328i Coupe can be frustrating. This issue prevents you from reading diagnostic trouble codes, monitoring engine parameters, and performing essential maintenance tasks. If you’re facing this problem, this guide will walk you through a systematic troubleshooting process to help you pinpoint the cause.
Before diving into more complex diagnostics, it’s always wise to start with the basics. Have you recently performed any work near the OBD II socket or the Junction Box Electronics (JBE) and JB Fuse Panel since the last successful code reading? Recent modifications or repairs in these areas could be the source of your communication problem.
Initial Diagnostic Steps
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Generic OBD2 Scan Tool Test:
The first step is to determine if the issue is specific to your advanced scan tool or a more fundamental communication problem with the vehicle itself. Try using a simple, generic OBD2 scan tool. These basic scanners are designed to read Engine Control Unit (ECU) codes in any vehicle sold in North America since 1996 and are readily available or can be tested at most auto parts stores.
“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 a generic scan tool also fails to connect, it indicates a broader communication issue within your BMW’s OBD2 system, rather than a problem with your specific diagnostic software or tool.
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OBD2 Port Power and Ground Verification:
A functional OBD2 port requires proper power and ground. You can quickly check this using a multimeter.
“Both Check OKAY”
- Pin 16: Should have 12V+ power at all times. This is the battery voltage supply to the OBD2 port.
- Pin 4 & 5: Should be ground pins.
- Pin 1: Should have 12V+ power when the ignition is switched ON. This is the ignition-switched power supply.
If any of these power or ground connections are missing, investigate the relevant fuses and wiring for breaks or shorts. If power and ground are confirmed, the issue may lie within the communication lines themselves, specifically the D-CAN line in this BMW model.
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D-CAN Line Continuity Inspection:
The D-CAN (Diagnostic CAN) line is crucial for communication between the OBD2 port and the vehicle’s electronic modules, including the DME (Digital Motor Electronics). For the 2007 BMW 328i Coupe, the D-CAN line is often the culprit in communication failures.
To check continuity, you’ll need to inspect the wiring between the OBD2 port (connector X19527) and the Junction Box Electronics (JBE) at connector X14271.
“It is the blue connector (towards left or drivers side) and yes there is continuity between #7 and #33”
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Locate Connector X14271 at the JBE: Remove connector X14271 from the JBE. Inspect the pins and sockets for any signs of corrosion or damage, paying close attention to pin #33. Pin #33 is where the D-CAN line from pin #7 of the OBD2 socket (X19527) connects to the vehicle’s bus system at the JBE bus portal.
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Continuity Test: Using a multimeter in continuity mode, test for continuity between pin #7 of the OBD2 socket connector (X19527) and pin #33 of the JBE connector (X14271). Continuity should be present, indicating an unbroken wire. If there is no continuity, there’s a break in the D-CAN line that needs to be located and repaired.
Here’s the wiring diagram for the OBD2 socket X19527 (valid for models BEFORE 3/1/2007):
Alt text: Wiring diagram for the OBD2 socket X19527 in a 2007 BMW 328i Coupe, highlighting pin assignments for power, ground, and D-CAN communication.
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JBE Connector Location and Configuration (Pre and Post 3/1/2007 Models)
It’s important to note that BMW made changes to the Junction Box Electronics (JBE) configuration around March 1, 2007. This includes the location and potentially the pinout of connector X14271.
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Pre-3/1/2007 Models (like your 2/2007 328i Coupe): Connector X14271 is typically located on the inboard side of the JBE.
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Post-3/1/2007 Models: Connector X14271 is located on the outboard side of the JBE.
Refer to these TIS (Technical Information System) links for visual guides to the JBE installation location for both pre and post 3/1/2007 models:
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JBE Location – 2/2007 Models: https://www.newtis.info/tisv2/a/en/e90-328i-lim/1VnYoJSPhH
Alt text: Installation location diagram of the Junction Box Electronics (JBE) in a 2007 BMW 328i Coupe manufactured before March 1, 2007, showing the inboard connector position.
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JBE Location – Post-3/1/2007 Models: https://www.newtis.info/tisv2/a/en/e90-328i-lim/G8ns32Rq
Alt text: Diagram illustrating the installation location of the Junction Box Electronics (JBE) in a 2007 BMW 328i Coupe produced after March 1, 2007, indicating the outboard connector position.
Pay attention to the orientation of the large fuses in the lower-right corner of the fuse panel in these diagrams to correctly identify your JBE type (JBBF 70 or later JBBF 87).
Regardless of the JBE variant, the connector view for X14271 should be consistent. Here is the connector view diagram for X14271:
https://www.newtis.info/tisv2/a/en/e90-328i-lim/CTHz9Js2
Alt text: Connector view diagram of X14271, the JBE connector relevant to OBD2 communication issues in a 2007 BMW 328i Coupe, highlighting pin numbers.
Conclusion
By systematically checking these points – generic scan tool connectivity, OBD2 port power, D-CAN line continuity, and JBE connector integrity – you should be able to isolate the cause of the “No Communication” OBD2 error in your 2007 BMW 328i Coupe. Remember to always consult your vehicle’s wiring diagrams and repair manuals for precise information relevant to your specific model and production date. If these steps don’t resolve the issue, further professional diagnosis may be necessary to investigate potential DME or other module failures.
