If your 2008 BMW is experiencing a no spark, no fuel condition, the Digital Motor Electronics (DME) power supply is a likely culprit. This guide, using a 2006 325i as a similar example, outlines troubleshooting steps using the DME wiring diagram and related components like the DME Main Relay. A lack of signal from the DME to the EKPS (electric fuel pump control) often indicates a DME power supply problem.
Checking the DME Power Supply
The first step is to check fuse F54. This fuse provides constant battery power (Terminal 30) to the DME, allowing it to activate the DME Main Relay (K6300) upon ignition. If F54 is blown, replace it with a fuse of the correct amperage.
Next, if F54 is good, verify 12V+ at Pin #1 of Connector X60003. This connector receives power directly from the fuse. Absence of voltage here indicates a wiring issue between the fuse and the connector.
Testing the DME Main Relay
The DME activates the Main Relay by grounding Pin #13 of Connector X60005 via a White/Gray wire. This energizes the relay, supplying power to fuses F01-F04 and F06, crucial for engine operation.
To test the relay, apply a ground jumper to Pin #4 of Connector X6300 (the White/Gray wire). This simulates the DME’s ground signal. If the engine starts or you detect 12V+ at fuses F01-F04, the relay is functioning correctly. This also powers the DME via fuse F03, allowing diagnostic software connection.
Diagnosing with INPA/ISTA
With the DME powered, connect diagnostic software like INPA or ISTA. Utilizing INPA’s Functional Jobs (F2 Identification and F4 Fault Memory), you can verify DME communication and retrieve stored fault codes providing valuable diagnostic information. ISTA offers similar functionality.
Further Troubleshooting
If these steps don’t resolve the issue, further diagnostics are required. This could involve checking the wiring harness for damage, inspecting the DME itself for internal faults, or addressing a potential steering lock malfunction indicated by a warning light on the instrument cluster.
This guide provides a starting point for diagnosing DME power supply problems in a 2008 BMW exhibiting no spark/no fuel symptoms. Remember to consult a qualified technician for complex issues or if you’re uncomfortable working with automotive electrical systems.
