no high engine brake

[Swaid25]

Hopefully someone can help. Posted about low power after a few thousand miles on rebuild cm870 565 cpl8518
Cleaned back pressure pipe and thermostat housing. New sensors every where, new actuator control module and hose. Changed all egr hoses to intake ran good but no high engine brake for 10 miles then back to very low boost and high egt. Change ecm cause that was the only thing left that wasn't new. Now today I have full power and low egt. Every thing is going great. Besides my engine brake still isn't working on high had a guy plug up to truck with insite he didn't know much but did get to check the engine brake selection switch. And all 3 (33, 68, and 100%) showed up. Plus no fault codes I'm at a loss

[Chamberpains]

I forget, what year and model truck is this in?

I think you said it was a 9400i. But I may be mistaken. The problem you describe sounds exactly like the control module for the turbo actuator malfunctioning. what is the max boost pressure you are getting when you're Jake's are on high? What are they at on stage 2? What is Max boost pressure under throttle when it's malfunctioning? What is Max boost pressure when it's not malfunctioning?

I see you have replaced the control module but just to let you know it is not unheard of for brand new straight out of the box holset actuator control modules to malfunction. I know of two guys in the last year that had this happen to them. I'm not saying that's your problem for sure but if you check everything else and it all checks out okay then this may be a possibility.

It looks like your ECM is commanding the correct commands but the components after that are not responding correctly. If I were you I would step by step go down diagnosing to make sure that circuit is operating correctly. First off you need at least 90 PSI to the module itself. If this is a 9400i, under your driver's side cab there is a treadle valve attached to your brake pedal. The feed line to the control module comes off this treadle valve. there is a pressure reducer attached to the treadle valve itself. This may be plugged or not operating correctly. It is a son of a bitch to get to but simply make sure you have at least 90 to 120 PSI going to the control module. If not your problem resides somewhere in that chain. After that rig up a pressure regulator right after the control module into the airline with some shop air. Then run shop air from 0 psi to 90 PSI over to the actuator itself. Ensure that there is no leaks anywhere in that range. Make sure you have full clean travel of the actuator itself within that pressure range. It is not unheard of for the line that runs from the module over to the actuator to be pinched shut underneath the steel braided line. It is plastic line wrapped in steel braid. Check it out very closely. This circuit is ultra finicky. The slightest restriction will throw everything off. make sure there is zero debris in the tubing anywhere. Blow it out with clean shop air.

I believe you said you replace the harness to this module so that would exclude the wires being old. But it never hurts to ohm them out to ensure they are making proper contact. check the pins to make sure they're not recessed anywhere in the chain. The wires are only about 5 ft long and not hard to run out all the way back to the ECM. Cummins quick-serve also has the specs and a procedure on testing the harness. If you're not on it, it's free to sign up and get all kinds of handy procedures including the one for the harness.

[Swaid25]

Max boost on high is 20 at 1800rpm max boost on mid is 20 at 1800rpm. I can switch from high to med and no change. Now since I put new ecm I don't have any problems under throttle it'll pump 40psi if I stand on it above 1600rpm. Around 38 under 1600rpm. Been keeping boost between 15 and 30 most of the time. And yes I have an 06 9400i. I do have the book that tells me how to test the wires I did that b4 I bought the ecm. Didn't know about the treadle valve supplying control module. Will look at it. But I have no shop air. I'm on the road but I will put the old control module back on and see if it makes any difference. I just replaced the hose going to the actuator 2 nights ago. Making sure not to twist it or kink it. Thank you for your help

[Chamberpains]

20 psi is a bit high for 2nd stage jake. Mine won't peak passed 14 psi. I have a small CPL (8520) engine. I don't know if this makes the difference or what your 2nd stage being higher would mean. Im just stating that there is a difference.

When you cleaned the housing to the exhaust pressure sensor, did you ensure that no loose crumbs got blown back up to the sensor or reclogged anything.

Also having someone that knows what they're looking for with insite or calterm can make a world of difference. Maybe record a test drive using either one while monitoring all sensors. You more than likely have a slow j1708 diagnostic connection so you'll have to record a lengthy test drive on a pretty good hill. Both up and down it.

[Swaid25]

I'm trying to find a decent price inline 6 on the road. I have my laptop and can get insite for a fair price. I for get the part# for the brake out cable on the engine harness I can just run thro the firewall. You right about the slow if any connection with my dash data port. The shops and people that do hookup just about always have to connect under the hood. But with the back pressure sensor I left it out and plugged up ran engine for about 15 minutes taking it up to 1500rpm every now and then. Waited for it to cool down took pipe back off and tried to clean it again but it was clean put pipe back on and new sensor in. I'm wondering if 1 of the new brake rockers blow a seal and it's only braking on 5 but all 6. I have no clue. Never had a problem with engine brakes b4 not even on my old 60s that had 1.8 million miles b4 a piston fail apart.