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Loss of Jake, and other ECM related problems
Reference Yikes
-lost jake brake coming down Siskiyous pass
http://prevostcommunity.com/forum/threaddetails.asp?Category=Chassis&ThreadID=5114I may be able to add some information to the
conversation. This problem is not unique, a friend with a 95 Prevost has the same problems.I have lost my jake many times in my 97
chassis 98 Royale Prevost with a DDEC III Series 60. I use a Silverleaf
and laptop to watch various parameters that are going through the ECM, real
time. When I lose my jake, the ECM is
seeing a 6% throttle. Pulling the throttle up, or snapping the throttle, does
not change the 6%. However, as others have said, cycling the key
corrects the problem. I have changed the TPS many times, and cleaned ECM
contacts. The problem is corrected temporarily, but has returned.Possibly related, I also lose throttle
operation on occasion. But, I can
drive and accelerate using the cruise control. It appears that the ECM is seeing the TPS
movement, but the turbo is not responding.
I store numerous ECM parameters every second
through the Silverleaf and save it in an Excel file. By reviewing the
data, I cannot see a correlation of any of the parameters.I have switched ECMs temporarily, and it
appeared to correct the problem, just as cleaning ECM contacts appears to
improve the problem. I have taken my
ECM cover off to search for corrosion and/or deteriorating components. The interior of the ECM is pristine. Based on the assembly complexity, I
question if ECM rebuilders could do more than change a component, or Krylon the
ECM.I avoid changing parts to correct a problem
without analysis. I would like to know
how the ECM is working.1. Why,
when the ECM continues to see a 6% TPS, only a key cycle corrects the loss of
the jake.?2. Why,
when it appears throttle is lost, no turbo, operating the cruise, appears to
bypass the problem ?Does anyone know the ECM and its programming ?
Ed Roelle
810-516-9888
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5 Replies
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Ed,
If Ken is reading the threads he may have some insight. He is the DDEC guru.
Ken?
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Somewhere on a Detroit forum, I read how one would calibrate a new TPS for a DDECIII. Essentially, ignition on and then depress pedal fully three times, turn ignition off.
Now, this may just be a placebo effect but my jake issue has not come back in over 6 weeks on the road.
As many have mentioned here, just cycling the ignition has similar effect. Maybe the ECM reads the actual TPS value at startup and uses it as the idle value as long as it is not obviously out of range.
The link below discusses the voltages the ECM expects for the TPS (between 0.5 and 4.5V). If the voltage falls outside that range, the ECM recalibrates which induces a momentary power loss. If it keeps recalibrating you might get your power loss situation. Cruise would work because it does not rely on pedal input.
http://www.tenfourmagazine.com/2011/06/performance-zone/chasing-problems/
Gerald
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I hate
to say anything and jinx my good experience. But, I also would like to
add some information to my earlier post.I have, over
the years, had numerous problems with the jake not working, throttle
inoperative, and overtemp coolant that has shut me down. Analyzing
Silverleaf information, could not identify the problem.I did 3 things,
and after a few thousand successful miles, have had no problems.
Based on how often I previously had problems, I would have expected to
see many occurrences.1. I
removed the ECM DDEC III from the coach, and removed the back. Everything
inside looked pristine. I am skeptical that any non-OEM
“rebuilder”, is capable to repair anything inside. It appears
a very sophisticated assembly process was used to build when new. ECM
was resealed with polyurethane caulk, connections cleaned (even though they did NOT show
any corrosion), and reinstalled the ECM in the coach.2. I had
changed the TPS about 3 times. Each time, problems reoccurred after
awhile. Based on the suggestions by others in this forum, I reset the
TPS . Key on, pedal to floor 3 times.3. Now,
before cranking the engine, I always turn the key on, wait for warning lights
to go out, and wait for the speedometer and tach to cycle through their
motion. Then, I start the engine.I don’t know which combination of those items changed my experience, or if the stars just became aligned. I hope this
might help others.Ed Roelle
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The third one is most important turn key on and let things cycle on and settle then start the engine
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Ed, What Peter said. Never crank the engine until the computer has cycled through. It is only a few seconds delay but the ECM is looking at everything and “setting up” itself for the job.
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