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Topic: Wiring Diagram U300 DWG A-3376 (Read 1295 times) previous topic - next topic

Wiring Diagram U300 DWG A-3376

My book is missing this drawing.  Tracking down an Allison issue.  Also, can anyone confirm the type and part number for the 10 relays under the dash for Atec.  Are they all the same.  ECU is giving me code 54 with no shifting allowed.  Do relays go bad?  Any suggestions.  Thanks always for your help.
94 U300 off grid always on the lookout for a new modification.

Re: Wiring Diagram U300 DWG A-3376

Reply #1 –
Bob,

Yours is one of the few Foretravels that COULD have different transmissions.  Most 1994 U300's have the DD two stroke engine with Allison 4 speed.  A very late model 1994 could have either a Caterpillar 3176 or even M11 with Allison 4000.

And, the code (if Allison 4000) should have two sets of digits-- main code and sub-code.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Wiring Diagram U300 DWG A-3376

Reply #2 –
Bob,
The relays under the dash are very common, called "Bosch" or "auto" relays available at any auto parts store.  I do think they are all the same and they have a common pin out so they should be plug and play to replace.

Here's a schematic of that drawing number.  It came with my '91 that has a 300hp 6V92 and an MTB 648 transmission.
I don't know if you have this or not, but here's a card (two sided) that shows code 54 as "Latching Solenoid Chain"
I have no idea what that means.  The shows it's for 600 and 700 series.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Wiring Diagram U300 DWG A-3376

Reply #3 –
Yes, late 1994 may have 6 speed with CAT w/Jake or M11 (two made). Do you have the Detroit 2 cycle?  It should have the 746 four speed.

Pierce

Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Wiring Diagram U300 DWG A-3376

Reply #4 –
Bob,

You should have an Allison HT 746 with ATEC. Does the check trans light on the dash stay on?


Jerry
The selected media item is not currently available.
Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"

Re: Wiring Diagram U300 DWG A-3376

Reply #5 –
Yes the check trans light stays on.  I do have the 300hp 6V92 and an MTB 648 transmission setup.  Pulled the ECU on the front firewall and disabled all power to the coach, including house and start batteries. cleaned all connections with electronic spray cleaner. Waited overnight.  Put everything back in place and now no start on the engine.  ugh.  turns over, but will not fire.  the check trans light still on. 

Weird, engine was running fine, but the trans is a no go.  been in storage for 1 year.  check of all fluids ok.  did not check the trans fluid at running temp, but always good. 

My other thought was maybe a relay had gone bad to the engine to allow the engine to restart, but seems far fetched for these things to occur, one after another.  Can I take the Allison ECU to a Allision dealer without the coach for troubleshooting?

Thanks
94 U300 off grid always on the lookout for a new modification.

Re: Wiring Diagram U300 DWG A-3376

Reply #6 –
Bob,

It looks like from your photo and description of your engine and transmission that you have an earlier U300 with the rear radiator and not the side radiator. The engine was limited to 300 hp as the MTB 648 is out of spec with the 350 hp engine installation. Opening the rear engine door, you have no hydraulic pump, hyd motor for a side radiator, correct? No Jake brake, correct? This sounds like a 1991 or earlier.

Have you checked the DDEC code light under the dash top for codes? It will read out a code for low or no DDEC voltage at the ECU. Since the coach as been stored, is the coolant level above the low coolant level sensor? How about the overflow tank? DDEC code will also read this out. The engine won't start if the coolant is low. This has caught more than one member out.

The schematics for your coach are in the "media" section of the forum. The 12V coach schematic is B-2035 and I would recommend you download it and take it to a copy shop and have it blown up as large as they can do. It makes trouble shooting a lot easier. The ATEC schematic as you have seen is A-3376 and the DDEC is A-3376. To see these, navigate to page 2 at: http://www.foreforums.com/index.php?action=media;sa=album;in=194;nw;start=35

If you have a Pro-Link 9000, it will read the codes and ECU voltage. Failing that, the little bulb will work with the codes it blinks.

Assuming the coach was operating normally before you put it in storage, my bet is you have a little corrosion on a electrical component from year it's been out of action for the 648 Allison.

DDEC codes: ddec 2 flash codes - Google Search

Pierce

Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Wiring Diagram U300 DWG A-3376

Reply #7 –
I was able to restart the engine.  Stupid me left a ground wire off the battery that went to the ddec ECU.  duh. 

Back to the problem at hand.  I am still not able to shift gears.  I must have an Allison HT 746 with ATEC, my manual has some listing trouble codes with both trans types. 

I checked ground on the ATEC ECU, swapped out some relays, disconnected the finger control box, reconnected.  What else could I check before sending the ECU off for a $500 repair?

Thanks
94 U300 off grid always on the lookout for a new modification.

Re: Wiring Diagram U300 DWG A-3376

Reply #8 –
Bob, you still have not said if you have a rear radiator or side radiator. Rear radiator will have the 648, the side radiator, a HT746. Your rear side grill does not look large enough for the side radiator. When you open the rear engine door, is the radiator there?
What date is on the plaque on the driver's left?

When you lift the dash cover and flip the switch labeled "transmission," what codes does it bring up on the little light bulb?

Try going under the coach and checking/cleaning all the electrical connections at the transmission.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Wiring Diagram U300 DWG A-3376

Reply #9 –
I have a side mounted radiator.  Found some other paperwork showing it is a HT746.

Code 54 is blinking  (Latching)

I will check ground, disconnect and wire brush it clean.  I climbed under but cannot really tell where the electric wires enter the transmission. 

Thanks for the suggestions

94 U300 off grid always on the lookout for a new modification.

Re: Wiring Diagram U300 DWG A-3376

Reply #10 –
Bob,

Have you used our Foretravel Allison Code Manual that Berry put online? Here is the address: Allison Transmission Codes Manual  Looks as if code 54 has a lot of possibilities to troubleshoot. Attached is the screen shot of the code 54 fault code with all the sub-codes and things to chec

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Wiring Diagram U300 DWG A-3376

Reply #12 –
Quote from: bob swanson –
I was able to restart the engine.  Stupid me left a ground wire off the battery that went to the ddec ECU.  duh. 

Back to the problem at hand.  I am still not able to shift gears.  I must have an Allison HT 746 with ATEC, my manual has some listing trouble codes with both trans types. 

I checked ground on the ATEC ECU, swapped out some relays, disconnected the finger control box, reconnected.  What else could I check before sending the ECU off for a $500 repair?

Thanks

Bob,

I just spoke with Ken Williamson at AL-Trans in Mobile who worked on my trans a couple of years ago.  He did a great job and saved me lot's of $$$$.  My problem was inside the trans.... Check Trans light on and Code 32 (direction switches.)  It was hard to shift from neutral to drive or reverse (too much hesitation).

He dropped the pan, cleaned the valve body and replaced the switches.  Been working fine ever since. No rebuild needed!
Redirecting...

I asked him about the Code 54 and he said it could be several things but probably a wiring problem outside of the transmission.  He said water or corrosion could be on one of the connectors and to start by checking where the harness connects to the transmission.

Jerry
The selected media item is not currently available.
Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"

Re: Wiring Diagram U300 DWG A-3376

Reply #13 –
Jerry, great info.  Thanks.

 Is there anyway to clear the codes to see if it will throw this (54) again?  I checked ground from the ECU also ran up to operating temp and made sure trans fluid was good.

I will check all wires.  But am pretty sure it is not the ECU.  Good and bad. 
94 U300 off grid always on the lookout for a new modification.

Re: Wiring Diagram U300 DWG A-3376

Reply #14 –
Bob,

I'm not sure if ATEC works the same as DDEC II.  When the problem causing an active code in DDEC II is fixed then it will be moved to the historical codes and remain until cleared with a Pro-Link or some other diagnostic tool.  I don't have an ATEC cartridge for my Pro-Link 9000 and after the repairs on my transmission,  AL-Trans cleared the code 32 I had with an Allison DOC.

If the problem causing a Code 54 is resolved I believe that the check trans and do not shift lights would go out and it would shift normally unless other codes were triggered.  The code 54 would be moved to the historical codes and remain until cleared.

Jerry
The selected media item is not currently available.
Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"

Re: Wiring Diagram U300 DWG A-3376

Reply #15 –
Jerry has it exactly right!

Bob, the ECU (aka engine control unit) should not be confused with the ATU (aka transmission control unit). One is mounted on the engine with the other on the plywood front bulkhead/firewall.  Have you checked your shift pad?

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Wiring Diagram U300 DWG A-3376

Reply #16 –
Cleaned and inspected ATEC plug and wire harness at transmission.  Ensured that it was seated correctly and did not notice anything cut, loose or frayed.  No change in condition.  Still no shift key flashing.  Is the wire harness all one piece from the ECU on the firewall?  Maybe I send the ECU out to Texas, and have it checked.

Inspected shift pad and made sure all was tight and secure. 

Comments?
94 U300 off grid always on the lookout for a new modification.

Re: Wiring Diagram U300 DWG A-3376

Reply #17 –
Quote from: bob swanson –
Cleaned and inspected ATEC plug and wire harness at transmission.  Ensured that it was seated correctly and did not notice anything cut, loose or frayed.  No change in condition.  Still no shift key flashing.  Is the wire harness all one piece from the ATU on the firewall?  Maybe I send the ATU out to Texas, and have it checked.
Inspected shift pad and made sure all was tight and secure. 
Comments?
Have you checked for transmission fault codes using the under dash top light bulb after turning the transmission switch on? Is that where you got #54 fault code? Any subcodes?

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)
 

Re: Wiring Diagram U300 DWG A-3376

Reply #18 –
If the solenoid chain's resistance is okay, and individual solenoid circuits are okay, replace the ECU. If replacing the ECU fixes the problem, verify the old ECU is "bad" by reinstalling it, road testing the vehicle,and checking for codes.
ALLISON TRANSMISSION ELECTRONIC CONTROL TROUBLESHOOTING MANUAL
APPENDIX A — TROUBLESHOOTING STEPS - TROUBLE CODES PRESENT

If I had a replacement ECU to install I would be on my way to MX.  Will check wiring harness and solenoid resistance.  Thanks for the link to the download manual.  very useful.

94 U300 off grid always on the lookout for a new modification.