‘03 Freightliner Columbia, DD 12.7 series 60. “Low” braking works in low and high (same braking effect/sound). Nothing from other cylinders in “med” or “high.” Switch meters okay. Next want to check wiring from switch to ECM. Wiring has butt splices where goes to ECM plug. How is electrical connector fastened to ECM? Do I have to remove ECM from block? (Not sure if even issue on this engine but, I read Truckshops info to CraneOp re: oil pressure dropping out if galley plugs loose/missing. No change in oil pressure.) Thank you, Darryl
Manual does great job for r/r of hard parts but doesn’t have wiring schematic or electrical troubleshooting. Planning to have overhead run at some point but want to rule out wiring up to valve cover.
Well, pulled the plug on input side of ECM- a connector on one of the Jake leads was pushed back a bit from the other. Checked through both for continuity, used electronic cleaner then a little dielectric grease, seated connector and now sounds like I’ve got all my Jake’s working. Will road test at some point. Replacing some dash parts while I had it apart to trace wiring.
I'm guessing it has Jacobs 795 model brakes or equivalent. One thing that is a issue if jakes sound correct/working on all cylinders but are weak, the oil control valves can/will separate themselves {those are two piece}. Cutting the full flow of oil to the slave piston. The jake will sound correct at the stack, will not throw any code or turn on engine light but it will be weak-something to remember. The other is harness break down due to heat and oil.
That’s good info to have, thank you! Want to get it in to have the overhead run. Will asked to have that checked and probably replace that harness at same time. Keeping it all under 50k gvw, I’m not sure I’ll notice if weak (and having not run it before to know if different). I was a little apprehensive as to how deep I wanted to get into it. Thankfully was easy fix (if that was the issue). I can’t believe how much wiring and crap they pack under the dash! Thank you for your help with this.
It probably has tight intakes, which effect the jake also. Setting the valves will cure that. Last injector harness I bought was $140.00 probably $240.00 now. Wiring? that's 20 years old, you should see them now.
I can imagine