A lack of repair information often leads to difficulty in diagnosing even the simplest things. Without a road map, getting to the destination takes longer than it should.
Like this example of a small, inexpensive component causing a no start situation on a Mercedes Benz B200. Because it is a Canada only model, repair information through the usual sources is very limited. This video demonstrates how frustrating this can be.
First, a scanner is connected and an all systems scan is performed to see what, if any, modules are offline. It is immediately obvious that the Engine Control Module isn't communicating, indicating that it's not powering up. Because the other modules are online, we can assume that it is a module issue rather than a communication issue.
The next obvious step in the diagnosis is to find out why the ECM isn't powering up. In order to find the power and ground circuits, we next need to consult a wiring diagram. easy enough, consult the usual information providers. Problem is, information availability for this model is extremely limited, and wiring diagrams are unavailable.
Next step is to get a paid subscription through Mercedes for correct information. Generally, OE subscriptions are a simple process, but we ran into several delays for this model. In total it took over a month to receive the required information. When we finally got access, it took a while to navigate the site, but eventually the wiring diagram was located..
The newly available wiring diagram indicated a relay powers up two fuses that provides power to the ECM. Jordan located the fuse panel, which was located underneath the passenger floor, next to the battery.(!) Both fuses were not powering up, leading Jordan to suspect the relay.
Now, this is where it gets really interesting. The relay box is located in a difficult to access location, on the firewall behind the passenger side dash. Using a uActivate relay tester/simulator, Jordan tests the relay circuit. But which relay is it, and why is it not labeled correctly?
Demonstrating the importance of correct repair information, the problem is quickly narrowed down and solved.
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