Codes

[TheBac]

Truck went into limp mode on Tuesday last week at work (oh fun driving 25mph all the way home), and I hadnt driven it since. Weather has been cold/snow and when I looked under the truck that evening, the NSBU/T-case area was packed with snow and ice. Shift selector would blink and click in R and D, so I figured it was the NSBU. I went and replaced that, but the codes wont clear.


These are the codes.

P0840 "Transmission Fluid Pressure (TFP) Sensor A Circuit"
P0841 "Transmission Fluid Pressure (TFP) Sensor A Performance"
P0846 "Transmission Fluid Pressure (TFP) Sensor B Performance"
P0847 "Transmission Fluid Pressure (TFP) Sensor B Circuit Low Voltage"
P1711 "Pressure Switch E Circuit Low / Stuck Closed"
P1713 "Pressure Switch Reverse Circuit"



Truck seems to drive and shift fine now, but the CEL stays, even when the trans warms up.

Would weak batteries cause this? Ideas?

 

[ripmf666]

When you replaced the nsbu did they sell or have you ever switch out the 2 pig tails that plug into it they have all the same color wires hard to tell mybe the harness is bad. I replaced it after replacing the switch the 3rd time.

 

[TheBac]

No, did not, and have not replaced the harness leads. There was water in the plugs, though, which I dried out first, and used plenty of di-electric grease when I put it all back together.

BTW, 4wd does work, too. Trans fluid level is good, too.

Im going to head out in a bit for a drive to see if anything strange happens.

 

[TheBac]

Just got back, truck drove out same as usual. Shifts nicely as always. Odd.

I'll hav eto get under the truck again tomorrow night after work and check the Trans/Tcase plugs/wiring.

 

[Mike L.]

Sounds like you turned the ignition switch on while a connector was disconnected or an act of God.Those codes indicated a short in every solenoid you have. The fact that it works fine now tells me I'm right. The light will go away after a while.

 

[TheBac]

Thanks Mike.

 

[TheBac]

Trans did it again to us a couple times since the 19th. I figured out that if I shifted into gear before letting the trans warm up a bit, it would set the codes.

Called Merchant for advice. He said he was getting quite a few calls/service concerning limping/odd behaviors lately, and the common denominator seemed to be the trans low on fluid. When I had checked it before, the level looked fine to me. I do have a DS dipstick now...do they read a bit "off"?? Anyway, I added fluid (about 1/2-3/4 qt) and trans has finally started acting normally. Havent had an issue since. I guess we'll see.

 

[TheBac]

Trans just keeps doing it when temps get below 32*. Tonight, it acted like a manual with a stall speed of 2000rpm when leaving a light. Im taking it to Merchant tomorrow, and Im not looking forward to what we find. I think its hurt, but have no idea how it happened.

 

[Chevmeister]

You might just have water in a connector somewhere. "Trans just keeps doing it when temps get below 32*. " as you know im no allison tech, but electrical is one of my strong points. Ice while it is just water does not conduct good. If there is water that is freezing it will break the connection just enough to cause an intermitant problem. Dielectric also can cause problems. I do not use dielectric on our plow plugs any more because at about 20* it pushes conectors apart.

 

[TheBac]

Forgot to update...

It was low on fluid again. Almost 3qt low. Eric thought I may have a trans line seeping, even though I havent seen any spots on the driveway. Iill have to keep an eye on fluid levels until spring when I can replace the trans lines.



Henry, do you happen to know the proper trans line part numbers for a 2003 LB7? I looked on gmpartsgiant, and they show two different partial part numbers for each line. I am confused on which ones to order. Also, which one of our vendors would sell these lines?


1 **170217 HOSE TRANS FLUID AUX CLR INL,(INCLS 2),(CODE UCX) CK2,3 (LB7, M74, KNP) 03 1 $51.26 $36.17
*
1 **767598 HOSE TRANS FLUID AUX CLR INL,(INCLS 2),(CODE KTZ,KXJ) CK2,3 (LB7, M74, KNP) 01-03 1 $52.12 $36.78

---------------------------------------------------------------------


4 **170215 PIPE TRANS FLUID CLR LWR,(INCLS 2),(INLET)(CODE UCU) CK2,3 (LB7, M74, KNP) 03 1 $59.04 $41.65

4 **767596 PIPE TRANS FLUID CLR LWR,(INLET)(CODE KXH,KTY),(INCLS 2) CK2,3 (LB7, M74, KNP) 03 1 $66.86 $47.17


--------------------------------------------------------------------
5 **170219 PIPE TRANS FLUID CLR UPR,(OTLT),(INCLS 2),(CODE UCZ) CK2,3 (LB7, M74, KNP) 03 1 $66.79 $47.12

5 **767600 PIPE TRANS FLUID CLR UPR,(OTLT),(INCLS 2),(CODE KTW,KXK) CK2,3 (LB7, M74, KNP) 01-03 1 $81.26 $57.33

 

[JoshH]

Called Merchant for advice. He said he was getting quite a few calls/service concerning limping/odd behaviors lately, and the common denominator seemed to be the trans low on fluid. When I had checked it before, the level looked fine to me. I do have a DS dipstick now...do they read a bit "off"?? Anyway, I added fluid (about 1/2-3/4 qt) and trans has finally started acting normally. Havent had an issue since. I guess we'll see.

Forgot to update...

It was low on fluid again. Almost 3qt low. Eric thought I may have a trans line seeping, even though I havent seen any spots on the driveway. Iill have to keep an eye on fluid levels until spring when I can replace the trans lines.

So does the dip stick read wrong or what is the deal?

Henry, do you happen to know the proper trans line part numbers for a 2003 LB7? I looked on gmpartsgiant, and they show two different partial part numbers for each line. I am confused on which ones to order. Also, which one of our vendors would sell these lines?

Henry can get parts from GM.

 

[TheBac]

I have no idea, Josh. I doubt it. Mike would have never let a part with his name on it be wrong.

I think what happened the first time is that my driveway has a slight slant....not a lot, but probably enough to skew the reading so I read it wrong. Wouldnt be the first time I made a mistake, nor the last. That doesnt explain where the fluid went in the first place, though. Makes enough sense to me that the lines would leak at the crimps when the outside temps got low enough. The lines do have 163,000 miles on them now, so that may play into it.