02 Detroit DDEC-14 12.7 intermittent jake brake

Sometimes while driving along the jake will instantly cut out, as if it had been manually shut off. It cuts out anywhere from a split second to extended periods of time (minutes, hours even). Sometimes if I bump the jake setting switch from 3 to 2 or 1, it will come back on again. Sometimes it will work on 2/1 but not 3. Other times it won't work at all on any of them.

At first I didn't think it was weather related, until the last time I was going to take it to the shop. It had been consistently not working except for a few sporadic occasions for a couple of days straight. I figured perfect, finally I can get it checked out while it's NOT working. I gave the truck a quick wash before heading to the shop, and of course as soon as I left the wash bay it started working perfectly again. It's been working consistently except for a few stray hickups for about 2 weeks now. One of the only times it briefly cut out again was while driving through some wet slushy snow. It also seemed like each time the truck came back out of the shop (been in there 5 times for this now) the issues goes away completely for a couple of days and then starts to begin again.

I've been fighting with this issue for a while now, and of course whenever I've had the chance to take the truck to the shop, it's working fine. They've replaced switches, checked wiring and found/repaired a couple of suspect wiring issues but the problem is still there, they suggest it may be the ECM. Has anyone experienced anything like this? My concern is that after I buy an ECM, I won't be 100% sure if the problem is gone for a while, and if it starts acting up again a few weeks later I just wasted a lot of money on a new ECM. I'm puzzled how if the ECM was leaking or being effected by water/moisture, wouldn't there be other symptoms too? The truck is running perfectly except for this one thing.

The engine was inframed about 40,000 miles before this issue arose. Any chance this could be something under the valve cover?