Chasing ghost codes on new diesel engines is driving me nuts

I had a Freightliner with a Detroit Diesel that kept showing injector faults. My scanner listed three different codes, all pointing to the injectors. I pulled them all out, tested each one, and they were fine. After two days, I found a loose ground wire on the ECM. The computer was reading wrong because of a bad connection. Now I always check the wiring first, but it still eats up so much time. These new systems are too complex for their own good. I wish they made diagnostics more straight forward.

3 comments

3 Comments

murphy.blair1mo ago

Those ECM ground points on the DD15 are known for corrosion behind the firewall. The service bulletins don't even mention it until you dig into the wiring diagrams from 2018.

anna_white1mo ago

Had a bunch of those trucks come through the shop in Arizona and never saw that specific corrosion. The real headache on the 2015-2017 models was always the connector seals failing at the ECM itself, letting in road spray. You'd get weird voltage drops that looked exactly like a bad ground. Cleaning the firewall points was just part of the routine, but it was never the root cause.

margaret_stone1mo ago

Interesting! You mention the connector seals failing at the ECM. I've heard similar issues but mostly in humid climates. Have you found any reliable fixes for those seals, or is it just a replace-and-hope situation?