ATEC Problems

[NJT5049]

Hi all
I've had a problem with my ATEC I cant seem to resolve. THis is going back about a year now...
It all started when I parked the coach at a remote location during the winter. THe batteries had gone flat, they were removed for charging. Things went to hell when I reconnected everything. It seems that I connected the 12v positive for the ATEC to ground. When I flipped on the master I made smoke in the battery bay.
I've since replaced the ATEC, the key pad for shifting with a replacements from Nimco. The coach starts, I get a check transmission lite, she will move, shift thru the 'gears' once correctly once. After that all shift points are late. The error code I get is a TPS error.
Now the TPS I've checked. I think butch or JR said it should range from 500 - 1500 ohm. I've reset it so I get 500 ohm but only get as much as 1100 ohm full throttle. I had seen check engine light periodically previously so it is suspect.
I've replace or checked all fuses, the wiring harness as much as I can check it is intact.
I've contacted Luke for a replacement TPS and got the wrong part. It seems New Jersey Transit swapped it out years ago. The 'new' replacement part is $600 bucks. OMG lol
She's a 87' MCI9 New Jersey Transit. 6V92 Allison 740RT (ithink) Transmission, running a DDEC I.
Anyone have any suggestions?
-Tom

[NJT5047]

Hi Tom.  The saga continues I see.   
If you're setting a TPS code, the TPS is suspect.  Or the TPS wiring. 
What engine code was setting?   I remember the problem, but the details.....??   The DDEC and ATEC codes may give you some ideas.   
Are you setting the TPS code in the ATEC or DDEC ECM?
The VSS located on the transmission could be intermittant.  That would cause a shift problem.  The wires are probably hanging loosely above the VSS.  Located on the LH front corner of the transmission.   Should also set a VSS code?   
IF DDEC code also indicated a bad TPS, replacement of the TPS might solve your problem.   I sure hope so after spending $600 bucks.   Either way, it will rule out the TPS...  
I believe you'll receive a complete accelerator assembly. 
Post the results when you get the new TPS installed.   
One other item to check would be to look for linear resistance at the DDEC ECM.   I'd have to check, but I believe the ATEC gets the TPS signal from the DDEC ECM.
Damaged wiring, intermittant fuses in the battery compartment and I'm sure sundrous other expensive items could cause your problem. 
Butch has a SM for your transmission.  I'm planning on getting one..but??? 
NOW we're really going to miss Sammy! 
JR

[RTS/Daytona]

DO YOU GET idle and WOT (WIDE OPEN THROTTLE) on the engine in neutral ??

If not then check -->

The TPS for my DDEC-II  is 2500 ohms between the A-C terminals - The B-C and A-C terminal should vary between (100-600) at low end (1800-2200) at the high end

What your really interested in is that
#1 the voltage between PIN A of the TPS (SENSOR RETURN and PIN C (+5 Volts  supply) is TRUELY 5 volts
#2 the voltage between PIN A of the TPS (SENSOR RETURN) and PIN B (Throttle Signal) is about 4.25 at idle and .5 volts at WOT (WIDE OPEN TROTTLE)

If #1 and #2 are true - THEN CHECK IT AT THE DDEC PIN (not sure what pin on a DDC-1)



BUT YOU SAY THE PROBLEM IS AN ATEC ERROR not a constant DDEC error -

then I suspect it's the INTERFACE DEVICE BETWEEN THE DDEC TPS and THE ATEC
AKA DDEC/TECL INTERFACE DEVICE - I'll include a SIMPLE VERSION of the device that I have on my RTS DDEC-II to ATEC - IT's OEM FACTORY - housed in a little black box about the size of a DECK Of CARDS - It's a little device to isolate and share the TPS sigmal between the ATEC and the DDEC

on DDEC-ii (probably DDEC-III and IV) -  the TPS signal from the DDEC to the ATEC comes from a DDEC connection other than the TPS input -  it's called the PWM circuit 908 pin J3 (It is Similar to the TPS input ??) - I know a little wierd but ??  -- It goes via the interface box  to feed the ATEC TPS input pin 2P   

SEE INCLUDED POST

Pete RTS/Daytona  clear as mud - call me ...386..672.0571

[Kwajdiver]

When you say, "Key Pad for shifting" is this a push button pad with R, 1,2,3, D on it?   If so, wouldn't the tranny be a 741?  I thought the 740's had a t-handle for shifting.

Bill

[trailblazer2]

 Tom;
Welcome to the board! I have the same type coach,as well. You should have a 748 tranny in your unit. JR is the one that will probably benefit you greatly on this unit. He has certainly been a great help to me! What state do you live in?
Bill

[NJT5047]

When you say, "Key Pad for shifting" is this a push button pad with R, 1,2,3, D on it?   If so, wouldn't the tranny be a 741?  I thought the 740's had a t-handle for shifting.

Bill

Tom's trans is an HT748R.   That's the transmission used in all '87 NJT MC9s.  It is an ATEC with the push button shift pad just like yours.

Tom, the TPS is wired directly to the DDEC ECM.  J1A connector. 
Pin H3 in J1A should have 5 volts.   
Pin C2 in J1A is signal from TPS and will be something less than 5 volts. 
Pin K1 in J1A is TPS ground.   

The TPS plug under the drivers floor will be connected as follows: 
A=K1 (ground), 
B=C2 (signal),   
C=H3 (5 volts).

If your TPS is the fault, you should set a DDEC code '21' or '22'.   What DDEC codes are you setting?
An ATEC TPS code is the same as the DDEC ECM...'21', although I believe this is only applicable for HT741 trans with a TPS mounted remotely on the throttle linkage...such as Bill has.   If your ATEC reads a code '21', but the DDEC doesn't, the wiring between the ATEC and DDEC may be at fault. 
The DDEC 1 dx guide does not offer a resistance range.  It suggests using a 'DDL' reader...which we ain't got.  It counts pulses.  Try using Pete's reference.  May be the same TPS resistance for all DDECs?   
It doesn't appear that DDEC 1/ATEC use an interface.  Looks like the two ECMs communicate directly.   This may be inaccurate...but I have both schematics of the trans and DDEC and they only share a few wires.  The VSS is also processed by the DDEC. 
The wiring DDEC/ATEC connections are inside the upper rear bay...in that crap hole that is typical of NJT MC9s.  Mine appears to be in good condition, but moving them around scares the poop out of me.  Old wiring really doesn't like to be molested. 
Back to those fuse cases in the battery box...I've had an ongoing intermittant issue with the fuse holders and fuses.
They should all be replaced really.  But, it's one of those things that I know how to quickly resolve.  Still, the "Check Transmission' light has some pucker factor when it lights up way off from home! 
Have you had any kneeling, high idle, or other electrical issues?   These all interconnect with the transmission, although they don't set codes...they may if the DDEC senses speed when a limiter is 'on'...
I'd be rechecking the DDEC and ATEC for codes.  Remember that unlike a DDEC II, if you pull the fuse on a DDEC 1, you cleared the memory.   So make the codes set and read both ATEC and DDEC codes.   See what you get. 
If your windshields leak, you may well have a bad TPS.  Water running off the center of the dash drips on them...screws them up.  NJT also hosed out the floors regularly. 
Still, IF the DDEC isn't seeing TPS codes, the TPS probably ain't the problem. 
Until you re-read the codes on both units, the only other thoughts I have would focus on what electrical work was done on the coach prior to the onset of the problem?   
BTW, Butch has the resistance for a DDEC 1 TPS.  He checked his when his bus was acting up.   I can check mine too and see what it looks like.  Have to pull the spare tire out to access the connector, but that ain't much of a problem.   
JR 

   

[NJT5049]

Hi Gang;
Thanks for all the input . I'm off today so I should have a few minutes to tinker this afternoon.

JR - I am not clear on the pins your mentioning. I'm certain it's the the ATEC plugs, which is 1 or 2, I'm not sure. I haven't seen anything on the plugs indicating pin number. Can I call you later?

I don't recall the exact error on the DDEC. I believe this was determined as normal. I can re-post this when I get back from the doc.
TTFN
-Tom

[NJT5047]

The pins for TPS are on the DDEC ECM.  I'll give you a call later. 
JR

[NJT5049]

Thanks JR - I can call you toll free. Vonage - If that works.

I picked up a new digital Multi-Meter and have reset the TPS. I think the last number Butch and JR gave me for the DDEC I was 500 - 1500.
When it stops raining I'll hook the TPS back up and check voltages. I never concidered that before.

I disconnect the ground off the batteries for aqbout 5 minutes. One day I'll remember to mark witch switch is which :-). The code off the green light ( I think DDEC ) is 21, the Red, top light flashes 25.

The volatege between A and C are 5.3 volts at idle and full throttle.
I've looked again, my atec does not have the PINS numbered. I'll have a time checking that :-)

Trailblazer - I'm about 30 miles East of Cleveland Ohio. Thanks for askin

Voltages vary. Between a and c in 5.2 - 5.4 volts. voltage between the black and white were .5 @ idle and 4.62 WOT.

Ah Yes, Pucker power - Yep lol. I was about 60 miles from home at the time and that was my ride home. Kinda sucked.

I hope this helps and thank you all for your help!
-Tom

[NJT5049]

Hi
I spoke with JR this evening. The voltages all check out everything acts as it should. Our conclusion on the call was it was not the TPS. Jr suggested swapping the chip set in the DDEC back to the stock set. There was no differences.
The ATEC continues to blink a 21, the DDEC a 25 I still have a Check Trans lite on the dash. :-(

-Tom

[RTS/Daytona]

IIRC DDEC code 25 means NO ERROR CODES

Put your meter positive lead on ATEC connector J1B pin 1P  (throttle sense)

and your meter's negative lead on ATEC connector J1B pin 2P (return)

ANY OTHER voltage OUTSIDE of approx .5volts  to 4.5 volts (WOT to Idle)   WILL CAUSE A ATEC 21 ERROR

If the voltages are within that range - than YOU HAVE A BAD ATEC


 

[NJT5049]

Hi Peter

"Put your meter positive lead on ATEC connector J1B pin 1P  (throttle sense)
and your meter's negative lead on ATEC connector J1B pin 2P (return)"

Which set of connectors is this on the 6 wire connector or the large plugs that go into the ATEC? The plugs and wire are not marked back there. What REALLY surprised me is the plugs are not marked either.


Thank you in advance
Tom

[RTS/Daytona]

I sent the ATEC connector pinouts to your email addy - the file was too big to post

just look at the alignment ridges to determine which plug is which

[RTS/Daytona]

I tried sending you the file - sent it to the email addy you have listed in your profile

it bounced -- ask me how I feel about wasting my time and effort doing that - I tried to help - but

If you want the ATEC file with the pinout and connector discription

Then you have to send me a PM - I will only try - one more time

Pete -

[NJT5049]

Not wasted Pete - I got it! Curious about the bounce. Would you mind forwarding the bounce to oneil.tom@gmail.com? I'd like to research it. Which email address did you send to? I don't recall if I used my Yahoo or gmail address.

The file I received will be very helpful. I'll test tomorrow before I go to work.

Thanks again!
Tom