ATEC Problems

[NJT5047]

Hi Tom and Pete,
I would love to be included in the mailing of that PDF stuff on Allison ATEC. 
I'm at: njt5047@yahoo.com always works!
Thanks, JR

[NJT 5573]

Tom,

Sorry I don't have time to pull the book out today, but I remember that after you unhook or work on the TPS there is a procedure for the ECMs to relearn the TPS. This is done by turning the power on and off about 10 times to the units, then clear the ATEC codes and you are good to go.

[NJT5049]

Well - It looks like I may need a new (to me) DDEC. I ran the suggested tests today and am showing zero volts between P1 and P2. Now it's a little tight in there, I was a little short on time so I'll take another look tomorrow before I head into the office.
Anyone have a spare 1987 DDEC I for a NewJersey Transit they'd like to sell?

-Tom

[NJT5049]

A last note on this...
I dug into the wiring harness deeper today. I've found 5.3 volts going to the ATEC between terminals P1 and P2 today so the DDEC appears to be good. I went back to Nimco for another ATEC. I hope to see it soon.

Thanks for your help.
-tom

[NJT5047]

A last note on this...
I dug into the wiring harness deeper today. I've found 5.3 volts going to the ATEC between terminals P1 and P2 today so the DDEC appears to be good. I went back to Nimco for another ATEC. I hope to see it soon.

Thanks for your help.
-tom

5.3 volts is the driver voltage...would seem that the voltage would vary with the TPS position? 
Replacing the big parts is one way of resolving the problem for sure.   Hope that solves the problem.
You're on to something.  If the engine isn't showing a TPS code, but the ATEC is, that narrows down the problem considerably.   
The wiring between the ECMs is a possibility...as is the ATEC ECM. 
Since I've got the essential 'twin' to your coach (only 2 NJT numbers apart), any resolution to a failure is of interest!
JR

[NJT5049]

Well - I had really hoped this would be the last post on this topic. I'd have a solution, no check trans lite but no. Mr Murphy stopped by.
The ATEC came in today. I dropped everything to put the silly thing in and guess what! Same old thing. It did seem as though the tranny was slipping too.
I spoke with Nic at Nimco, he'll accept the ATEC back and is looking for a DDEC. He didn't seem as though he was very hopefull. So if anyone has a DDEC for a 87 NJT please drop me a line.
-Tom

[NJT 5573]

Tom,

If you only have one code and its the TPS then there is no reason to even consider buying a DDEC ECM if the engine is running OK. If you recalibrated the TPS like I told you and it does not work then you need another one based on what you have told us.

I know there is a rebuilder in Mn. that will surely beat the $600 price as well as trouble shoot your parts if needed for a reasonable cost. I next day my stuff there and its back in 3 days and repair is always cheaper than replacement.

My understanding of ATEC is that it really only needs information on throttle position to work with any engine combination.

No matter what you do to the ATEC, you must clear all codes by shifting N R N with the code sensor on before it will work again.

[NJT5047]

Both the DDEC and ATEC use the same TPS.  The DDEC supplies the TPS signal to the ATEC.   The DDEC isn't setting a TPS code....FWIW...?   AND, the engine is running normally. 
Could the DDEC be supplying an out-of-range TPS signal, while receiving a WNR signal. 
Wiring or plug issues with the wiring between DDEC and ATEC?
Just curious.
JR

[NJT 5573]

Tom,

Tell us how it sets the code, or if the original code will not clear. If the code clears, how does it reset? Is it immediate? Do you need to push D to reset it or do you have to drive it before it resets?

[NJT5049]

Hey Gang;
I tried a few things today:
I cycled the power on/off ten times. started with a check trans / TPS
Pulled the fuses then the above.
The above the shifted NRN.
The above the NDN.
These all net a TPS error. I'll double check tomorrow on the code upon first reset.
I started thinking about what JR said about the fuse holders and checked voltages across holder all except the bottom fuse holder ( brain farting can't remember what it is ) were 12.4 volts the bottom was 11.7 - weird.
Also the voltage DID NOT vary while the throttle was pressed. - Also weird.
NJT5573 - You mentioned rebuilding parts - What do you have in mind. Nic (Nimco) didn't seem to possitive on finding another DDEC.
-Tom

[NJT5047]

Since Tom has not answered this yet, let me try. 
When his bus is started, the 'check transmission' CEL lights up.  The bus will take off, shift thru all the gears once.   If you stop, the transmission won't shift correctly again until the engine is shut down and the system reset. 
Then it repeats the process. 
My thoughts (nothing more than a SWAG unfortunately) is that the TPS is working correctly.  The engine works just as it should.  Correct idle speed, and full throttle operation. 
Tom is working with a DDEC 1/ATEC HT748R.    There is no PWM that I can see.  Just a wired com-link between the DDEC and ATEC.   
The DDEC must be sending data beyond just a TPS signal as it is read by the DDEC unit.   If not further data, the engine wouldn 't know when various loads requiring downshifts occur.   So the TPS signal sent to the ATEC is modified by the DDEC in some fashion.   The DDEC maps have additional influence on the shift points. 
Tom had an 'upgraded' EEPROM (DDEC 1 can have HP and RPM parameters altered by changing the EEPROM).
This has been ruled out as a fault since he's replaced the new EEPROM with the old unit. 
The fault may have been induced by attaching the 12V DDEC/ATEC feed to the 24V post.   When this happened, it smoked up the battery compartment.   
The ATEC ECM has been replaced twice.
Looks like the latest ATEC Tom installed is working worse than the 'second' unit.   
It is possible that the ATEC output circuitry (drivers) in DDEC ECM is damaged.  I don't know.
On an NJT, the wiring between the DDEC and ATEC are easily accessed and to the extent of the data available, checked.   The wiring appears to be intact. 
That's what's going on.   
The DDEC 1 units are quite a bit different from the later DDEC II units.   DDEC II is a much more sopisticated system.  However, DDEC 1 units are not known for 'DDEC' failures.   They are known for having wiring issues.    Most NJTs have decent wiring.  The ATEC and DDEC ECMs are located in the rear bay so no weather or heat issues. 
Regarding the higher HP EEPROM, Butch and I are both using these EEPROMs with no problems.   They've been installed for 3 or 4 years now.   I would assume that the 24 volts has smoked something...any ideas are welcome!   
At this time, Tom's looking for another DDEC ECM to try.  That will rule the DDEC unit out.  It still could be the TPS, but if so, the DDEC ECM isn't setting a trouble code.  It flashes out '25' which is the 'normal' or the expected normal operation mode code.

JR 

[NJT5047]

OOPs...There's TOM!   
Tom, have you called Sam Caylor and Luke?   Luke has parted out several NJT/DDEC 1 coaches. 

[NJT5049]

Thank you for the last post JR.
One clarification. The 12 volt lead for the ATEC was connected to the ground port ( most left in the battery box ) and not 24V +.
I found this morning that by only flipping on the battery, master ignition off I have a faint light on the DDEC error code light when that switch is thrown to read the code. I spoke with JR regarding this and we feel as there is an electrical issue somewhere in the coach... code possibly be DDEC but...
Anyway been fighting migraines the past couple days, my mental capacity is... well fuzzy. I look at this again in a day or so.
I took it out to get fuel before it shoots up for the holiday. I noticed my Not Gen light flicker while getting off a ramp. Dam
-tom

[NJT5049]

I snuck the coach out for the weekend. All freeway until the last few miles which were 35 MPH .
I had the same shift problems pulling out of town, pulled off just before getting on the freeway, restarted and the coach shifted up fine. When I made my last turn off US422 onto OH282 and accelerated the shifting was on the money. Same deal on the way home. I got off US90 onto OH44, no problems, got off at OH84 to some back streets home and it shifted on the money.
Now JR and I were talking before about the problem maybe electrical ( a short someplace ) since we found the DDEC error light would come on with the battery hot, ignition off.
Been fighting migrains the past several day so crawling in the rear bay is the last thing I've wanted to do but I'm betting it's a bad ground come place.
More later!
-tom

[NJT5047]

Hi Tom.   Definitely an interesting problem with the DDEC CEL.
As described, pull the J1A plug and if the light goes out, it ain't a wiring problem.  If the light stays on, that would probably be good...I think.   Finding the 'feedback' or short might be an unfun job. 
It seems possible that the DDEC may have suffered an insult when the B+ was connected to ground and the ignition turned on.   Misplaced battery leads have screwed up several coaches.     
Regarding the 'No Gen' light when the coach bumps an idle...mine's done that since I've had it.  Typically when leaving an interstate or something where the batteries are fully charged.
Scared the 'P' out of me when I first noticed the light flash.   But it seems something that they do. 
I've got a marine 24V, 20 A charger hardwired to the house batteries.  When the genset is running, which I gotta do for OTR AC, the charger must be turned off or the 'No Gen' light stays on. 
Have you considerd buying a 'donor' coach?  If you plan to keep the '87 for a few more years, could be a useful item?! 
Now go take some Maxalt hits and get to work!      Keep us posted!

JR