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Author Topic: What sensors does DDec use to optimize engine performance  (Read 4088 times)
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1995 Prevost H3-41, series 60, B500 Allison

« on: April 29, 2006, 09:02:48 AM »

I just bought the PC based package from Silverleaf that allows me to connect to the engine and transmission electronics to look at and track every available parameter. I have a 1995, and of course its Detroit Diesel so there are not sensors available for every option in the software. The software is free, but the box and cable that connects it is $395. For those of us that are guage readers, this is a great setup.

Several of my sensors seem to be flakey - not too surprising due to the age of my coach and its exposure to salt. I intend to track them all down and replace all that are not working correctly.

My question if anyone knows it, is What sensors does the engine computer use to optimize running performance?

Some of the data available are

fuel flow
accelerator positon
oil temp
oil pressure
trans oil temp
coolant temp
fuel temp
battery volts
cruise speed
engine hours
engine load
road speed
rolling MPG
total miles
turbo boost pressure
intake manifold temp
peak braking
relative humidity

While these are not all that the software has available, you get the idea. Further, just becasue the software has an entry, does not mean that there is a corresponding sensor to feed it. The softwware can run with many different versions of Cummins, navistar, Catepillar, DD etc

For example my tach sensor is not always reliable, and when the engine gets up to operating temp, the oil pressure and temperature sensors go bonkers

I suspect that the faulty tach reading is the cause of the transmission shiftting roughly at times.

So, is it RPM, load (or maybe accelerator position) temp, boost pressure?
« Last Edit: April 29, 2006, 09:31:45 AM by H3Jim » Logged

Jim Stewart
El Cajon, Ca.  (San Diego area)

Travel is more than the seeing of sights, it is a change that goes on, deep  and permanent, in the ideas of living.
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Posts: 523

« Reply #1 on: April 29, 2006, 06:58:40 PM »

Jim, here's a list of sensors that DDEC uses to control engine performance.
Your coach should have DDEC III.
1- TBS - Turbo Boost Sensor
2- Fuel Temp Sensor
3- Air Temp Sensor
4- Oil Temp Sensor
I would want to monitor other parameters also, coolant temp, oil pressure,engine rpm, etc.
I know nothing about the Silverleaf product, I only use my Pro-Link or DDDL to do my diagnostic work.
You mention that several sensors seem "flaky", can you be a little more specific?
I recommend to check all sensor connections and the two 30 pin connectors that secure to the DDEC computer.
I have found the wiring harness on the vehicle side of the ECM (side closest to the transmission on your coach) to sometimes be damaged, worn insulation, wires broken inside the insulation. Give it a real good inspection.The engine harness side usually is in good shape.Fixed a few tachometer problems this way.Hope this helps you.
Send e-mail if you need more info.Good luck.
Sammy Cool

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Jim Shepherd


« Reply #2 on: April 30, 2006, 02:45:34 AM »

Jim, the latest Silverleaf software (2.2a -- you should have) has an option under the "Advanced" dropdown menu that is called "PID sniffer".  I have not played with it yet, but it will tell you what all data you can display according to the great folks at Silverleaf.

For those of you who want to know more about this great product, you can go to:


I am not affiliated with this company (wish I were, as I have sure sold a few systems for them Smiley)


Jim Shepherd
Evergreen, CO
85 Eagle 10/Series 60/Eaton AutoShift 10 speed transmission
Somewhere between a tin tent and a finished product
Bus Project details: http://beltguy.com/Bus_Project/busproject.htm
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