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4l80e/6.5 NA limp mode??

Roberttx13

Member
Messages
34
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19
Location
Odessa Tx
  • Hello all new here to the forum not sure if this is the correct spot to post anywho I'm having an issue with my newly purchased 6.5l Naturally aspirated 4l80e combo in a '95 Air Force box truck. I bought it from a friend not running as the battery's we're removed because of a charging problem, it would drain a battery left not running for 3-5 days. The truck has 42000 miles on it. Before getting it running I replaced 2 pulleys the serpentine belt , fuel filter, oil cooler lines top and bottom, oil and filter and soddered alot of wires that rats had eaten away at pretty badly. Truck fires right up after purging the injectiors and 2 new 600cca batterys ran good and idled pretty rough for 20 minutes I added alot of Lucas and some farm diesel and it cleared up.. come test drive time it seems the trans isn't shifting either out of 1st or out of 2nd I have reverse and 1 forward gear so I come back drop the pan and it's nasty brown pink and like water thin no burnt smell just really old fluid so I replaced filter added 5 qts and tried it after that it shifted great for 2 weeks I go out of town for a week and the truck won't start again and battery's we're reading 6 volts I charged everything up tightened up a not so snug ground on the front battery and it started up now the ses light is on and wouldn't you know it back in damn limp mode.. I drove it to a local auto store and where over the phone they assure me that they have an obd1 reader so I lug it a few miles to the parts store trans hit 230 on the gauge(mechanical autolite) measured at the outlet of the trans pump. They couldn't read my vehicle on their reader so fusterated I drove it back home trans at 210 for 5-7 minutes and shut it down...next I tried the paperclip meathod by jumping terminals a and b on my 12 pin port and nothing happens no 12 code no nothing the ses light just remains on so in vein I pulled the pan off the transmission again replaced filter and changed solenoids a and b as well as the vss input sensor on the side of the case slap it back together and nothing still in limp mode...I checked the plug and I have one pin hole of the plug that reads 12.4 volts so the transmission has one hot location on the plug is this correct or shouldn't a few other holes show hot? I've checked the wire for breaks and chaffing and everything in between. What can I do to get this thing out of limp mode?(an assumption) it's also worth noting that even though the truck won't up shift no matter what gear I have it in if I pull it from drive into second it kicks down like it was in gear but it's like that gear doesn't exist and it will only kick down if it's very part throttle if I'm accelerating and shift it manually up or down it does nothing reverse works flawless and engine is very responsive and alot of torque but it's just not upshifting. How can I read the codes or at least reset the 4l80e to get it out of limp mode? I've taken the negative terminals off and let it sit for 10 minutes to 1 hr and each time the ses light returns and it's still limping. Any help or advice is greatly appreciated a local shop said they have a quality obd1 reader but if they can't read it it'll still cost 80$ which is sort of crazy to me but they're almost the only person in town that will even look at it. I'd love some advice on this transmission thanks again!!!
 
Welcome to the site.

I am suspicious of the repaired wiring and possibly other wiring issues.
I once did a trans filter change and pinched an interior wire. Couldn’t find it for a long time.

Double check the tps adjustment.

Don’t waste time at a generic mechanic shop. Find a good trans shop somewhere near you when dealing with trans problems.

Maybe some help from @THEFERMANATOR
 
Welcome to the site.

I am suspicious of the repaired wiring and possibly other wiring issues.
I once did a trans filter change and pinched an interior wire. Couldn’t find it for a long time.

Double check the tps adjustment.

Don’t waste time at a generic mechanic shop. Find a good trans shop somewhere near you when dealing with trans problems.

Maybe some help from @THEFERMANATOR
Thanks alot for the tip and where would the tps be on this vehicle I've checked the pedal it's only hooked to the throttle linkage. And how would I test the internal harness I plan on replacing it regardless it's 35$ on Amazon...also I have a little fluid in the plug not leaking out to tell ground but there's definitely atf in the harness plug and in all the holes of the plug could this cause a situation like this?
 
Welcome!

Full Stop on operation of it till it's fixed! Limp mode and your description is NOT locking the TCC. The extra heat from this will burn the trans down.

Paper Clip... Make sure you have correct pins. If you look close enough the letters are on the ALDL. Molded in black . You will be measuring voltage on it next and then correcting the ECM ground or 2 power feeds next. The ECM will not go into diagnostic mode if the voltages are too far out or bad high resistance open wires to the ALDL.

Simply put the paper clip had better work or you are wasting time on other things. Pissed off ECM from bad volts needs to be made happy before its fixed.
 
Welcome!

Full Stop on operation of it till it's fixed! Limp mode and your description is NOT locking the TCC. The extra heat from this will burn the trans down.

Paper Clip... Make sure you have correct pins. If you look close enough the letters are on the ALDL. Molded in black . You will be measuring voltage on it next and then correcting the ECM ground or 2 power feeds next. The ECM will not go into diagnostic mode if the voltages are too far out or bad high resistance open wires to the ALDL.

Simply put the paper clip had better work or you are wasting time on other things. Pissed off ECM from bad volts needs to be made happy before its fixed.
I'll remove the port tomorrow to see the letters on the back of the unit and make sure I'm in the proper holes... And what voltage should I see at the obd1 port? I can't get a test light to come on no matter what part of the port I check and I've heard that they may or may not have a positive feed(12v) so I'm a little confused there and as for the ecm I can't find it ...I want to check the wires and plug but I can't seem to find it even with the passenger dash taken off...would this truck maybe just have a tcm since it's manual injection or is it for sure I have a computer? Aside from wiring could the tcc solenoid be out causing this? Thanks so much for this info I'm making up my checklist for tomorrow and I won't drive it anywhere
 
See if the engine code in the vin is Y . If so , this is not OBD but a TCM only for the trans . I took some parts of a 95 G van and it sounds like what you have . Before that I thought everything after 93 was OBD but this was not the case .
 
See if the engine code in the vin is Y . If so , this is not OBD but a TCM only for the trans . I took some parts of a 95 G van and it sounds like what you have . Before that I thought everything after 93 was OBD but this was not the case .
It is for sure a Y Vin code. Thank you for clearing that up for me so could that be why the ses light won't flash codes? Where can I find the tcm? So without the obd can it still be diagnosed for codes?
 
TCM should be where the ECM is , they both look the same , behind the glovebox . I would check the fuses first , see if you have any blown . The 95 van manual I'm using ( don't have a truck manual ) has 3 fuses : ECM-Bat , ECM-CRANK and ALT Fuse . The ALT powers the MIL light . There should be 3 connectors in the ALDL , looking in 2 on the top right and one below on the right . The top 2 should be connected for codes but the MIL light has to come on when the key is on . Otherwise I would think a scanner should work .
 
TCM should be where the ECM is , they both look the same , behind the glovebox . I would check the fuses first , see if you have any blown . The 95 van manual I'm using ( don't have a truck manual ) has 3 fuses : ECM-Bat , ECM-CRANK and ALT Fuse . The ALT powers the MIL light . There should be 3 connectors in the ALDL , looking in 2 on the top right and one below on the right . The top 2 should be connected for codes but the MIL light has to come on when the key is on . Otherwise I would think a scanner should work .
I've checked all fuses and everything looked good there.....so I do have an ecm then? Or just the tcm? And I've jumped the 2 upper right terminals on the 12 pin and nothing flashed unfortunately..if it's possible I'd love to have a pic of the wiring diagram to the transmission to the tcm and I'll pull the dash tomorrow and look for the tcm..thanks again for your help
 
Take some pictures and post. I suspect you do not have a ecm. only tcm which would be somewhere under the dash area not it engine compartment.

I suspect you still have obd - being obd1 take a picture where you are jumping the pins. take a picture of your injection pump and water pump please. I think he misspoke when saying you don't have obd.

be ready to take a picture of the dash gauges and turn the key to the on position. snap the pic when everything lights up in the test mode.

take a pic of the passenger side front of engine below the exhaust manifold- this is to see if mechanical of electric fuel pump- yours could be either. if not familiar with where- ask and we can post pic of where the mechanical lift pump would be.
 
Take some pictures and post. I suspect you do not have a ecm. only tcm which would be somewhere under the dash area not it engine compartment.

I suspect you still have obd - being obd1 take a picture where you are jumping the pins. take a picture of your injection pump and water pump please. I think he misspoke when saying you don't have obd.

be ready to take a picture of the dash gauges and turn the key to the on position. snap the pic when everything lights up in the test mode.

take a pic of the passenger side front of engine below the exhaust manifold- this is to see if mechanical of electric fuel pump- yours could be either. if not familiar with where- ask and we can post pic of where the mechanical lift pump would be.
Okay I'll get all those photos on here for y'all soon and thanks for all the input guys this is helping me out major and I'm not familiar with where the lift pump may be but I'll get pics of everything else. So how can I have an obd1 and no computer so the obd1 may only run the tcm? Thanks again and I'll post back with photos
 
I should backup a minute . When I said you don't have OBD , I was referring to a DS4 pump . You should have a DB2 pump so very little sensors . The TCM does have OBD and you can pull codes . I would be looking for a blown bulb in the dash or maybe a TRANS light for the codes .
 
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The rest of it
 

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Just found this under the drivers seat of all places tcm? And reman with just 44000 miles I don't like that... What is this thing?
 

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