DDEC CODES & QUESTIONS

[Gerry H]

Hello All:
   I have been having periodic trouble codes showing up on my check engine light and shutting down my engine unless I press my engine override switch. So I turned on my DDEC test switch and read the following codes. 44-45-46-43-85-16-35 in order. I don't know what 46 & 85 are. If you do, please let me know. I know what the rest are. What I can't tell is how long any of them have been stored in the EEPROM and which one is randomly affecting me now. Some could be old and problem corrected, but not erased from memory. I know 35 & 45 are oil sensor related, and 16,43, and 44 are coolant related. I have some DDECII block diagrams, but they are incomplete.
   I'm optimistic that everything on the engine is ok, (semi recent rebuild) with just some bad connections, sensor issues or TLC needed.
   Can anyone tell me, or send me a diagram of where the DDEC sensors are located so I can start with cleaning contacts and connections before changing out the sensors. I have a 1992 8V92 DDECII in my LeMirage XL Prevost. Thanks Gerry H

[luvrbus]

Gerry, 46 is low battery voltage 85 is engine overspeed 


good luck

[NJT5047]

Codes 43 and 44 will both shut down the engine.   Code 43 is common.  The low water sensor is located in a surge tank, but cannot help with location on a Prevost.  The sensor will fail and set codes. 
Code 44 is overtemp. 
Some of the sensors are driven by the same 5V drivers.   You have a number of shut-down codes setting.  I'd look for a loose DDEC plug or maybe an engine harness that's loose or corroded. 
And, obviously, verify that the engine isn't overheating, and that the coolant surge tank is at correct level.   Apply the "bathtub" failure graph to a recently rebuilt engine....it is more likely to fail during the first hours of use.   
I believe you'll need a ProLink to wipe the codes.  DDEC II and III store the codes in a fashion so that an operator cannot clear the codes.   
JR

[NJT5047]

I should'a mentioned ground leads too.    Coolant surge tanks have low water, sometimes a high water sensor, and maybe a temp sensor that the DDEC monitors.   A bad or loose surge tank ground would lead to faulty data.   The surge tank should have a dedicated chassis ground, in addition to the DDEC ground.  Often the DDEC ground is bonded to the tank.
Any recent electrical work on the engine?   
Code 35 is faulty sensor voltage...just saying the reading is outside normal limits. 
What are you doing when the code 43, or other shut down codes, set?   
The overspeed code is unusual on a bus.  That generally means RPM greater 2500 for a few seconds.     
The "low battery voltage" is common and usually cures itself. 
JR

[Ace]

From personal experience, check your breakers and wires going to and from. I had a shut down problem that plaqued me for 3 years until one day (very frustrated) I accidentally found a LOOSE wire right at the breaker for low coolant. Once I tightened the loose screw, I have NEVER yet had any problems with ANY codes and I had as many as you do now if not more.
It's true you will need to own or find someone that owns a Pro-link with the DDEC 2 cartridge in order to erase history codes or relate what recent one/s you have.
Since you state that you had a semi rebuild, check for bent and or corroded pins on the ECM. It's very easy to bend the pins while connecting the harness! Also if your connectors show any green color, they need to be cleaned. DD sells an electric connection cleaner that simply sprays on and dries. Works good and eliminates moisture as well.
Also do yourself a favor and buy a DDEC diagnostic book which will guide you step by step to find a possible problem. You can download the codes from the internet also!

Ace

[Gerry H]

JR - Ace: I was simply on high idle at my house when the code/codes set. I was probably responsible for the low battery code (was before I got a smart charger) and ran down the batteries. P.O. is suspect for the engine over speed, and P.O. froze it up in Canada with no antifreeze, (west coast owner) cracked block, Prevost No. Calif installed rebuilt engine. Possible they didn't clear temp/coolant codes at that time-guessing here. I also suspect there's 15w-40 oil in it which could have affect on the oil sensor codes at idle, need to find it(sensor) and clean it first, then change oil to straight 40w next spring.
   I started cleaning all sensors and contacts, but don't know which is what. I am an electronics tech by trade, so with the right info, I can trace it out, just don't have the location of the sensors and which are for DDEC and which are for the dash.
   My favorite electrical contact cleaner is De-oxit 5% by Caig Labs. Been using it for along time. Engine has shown no signs of overheating, can't hardly get the stats to open idling, dash and eng compartment gauges show around 175.
No electrical work done to engine since I've owned. (9 months) Thanks for info  Gerry H