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Jake brake issue
In the year or so we have been having problems with the Jake Brake. Everything starts out fine and then a some random time (10 mintues or a couple of hours) the Jake will stop working. Stopping, shutting down and restarting restores the Jake function. We recently had the ECM replaced for another issue but it did not solve the problem. The weird part is that when the Jake is working the dash warning light comes on slightly when engaged. When not working the light never comes on.
Usually, the Jake will then function the rest of the trip, but not always.
Anyone gave any thoughts?
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10 Replies
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Well looking at how it is intermittent it has to be something electrical. Have you pulled the valve cover and looked at the wiring to the solenoids? I’m sure you’ve gone through checking relays and circuit breakers already. Thats seem to be a tough one, but if you haven looked under the valve cover it probably wouldn’t hurt to take a look.
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Bill:
Just parenting, what I read in other post…
Sounds like a loose or bad wire, most likely under the valve cover.
Chuck
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No, have not removed valve covers. Would have to have Prevost or some professional do that. Seems weird that a loose wire would fix itself just by shutting down and restarting. Fulltiming does help either as I rarely have down time to get it to someone who could dig in. As to relays and the like, i don’t know where to look but could if you have some ideas. I know the 1988 coach had a separate Jake Brake module. Is there such a thing in a 98 and where would I look?
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A couple of thoughts,
Be sure a floor mat is not keeping the gas pedal from coming all the way to idle or even a pebble or something.
be sure the brake lights are working with no failed bulbs.
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Hey Bill….I would start in the rear electrical junction box. It should have a schematic on the box door when you open it that will list the breakers and relays by number. I have an older chassis (92) and mine is located middle back top of the engine, not sure exactly on the 97 chassis but you should be able to find fairly quickly. There may also be a breaker in the front compartment under drivers seat. On my chassis I have a breaker up front and the relay is in the rear junction box. I haven’t figured out yet the correlation of having one up front and another in the rear box. I think the rear relay has something to do with the brake lights with the jakes activates.
Jeff and Lindsay
91 Marathon XL -
Mine would quit randomly like that for years and always reset when I shut down the engine and restarted. My ECM and wiring to the Jakes were changed for different causes but the Jake problem remained.
The Throttle Position Sensor (TPS) that is mounted to the back of the “gas” pedal. It sends the position of the throttle to the computer. It determines how much fuel you pour into the engine and makes it go faster. It also affects the cruise control and the Jake.
When the Jake quit again. We stopped at a rest area, but did not turn off the bus. Instead, we unplugged the TPS and then plugged it back in. The Jake worked perfectly! BINGO!
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The TPS is normally easy to replace. Two screws and an electrical plug removes the old one and two screws and an electrical plug installs the new one. The piug end may be different but the TPS came with a new harness and it was an easy change. It plugs in under the floor.Davy -
You symptoms are like the ones I had. FYI There is a wiring harness under the valve cover that over time breaks down due to the heat. I’ve replaced my on my Cat engine works great now
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new tps fixed my Jake issue that was random as well
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Thanks. TPS sounds like a cheap easy way to start looking for the issue.
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What is the part# for a TPS? I might buy one and put it with my extra parts
Joe Wilhelmi
1998 Country Coach
Dixon,IL
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