tonyvisone

hi guys. desperate for help here!

99.5 silverado 5.3, 4l60e, np246

i blew the trans. i bought a used trans with transfer case. i was told it was working great. fluid was mint.

i put them in the other day. now my speedo doesnt work and i get a speedo sensor circuit low code P0502.
the truck revs high (like to 3k) before it shifts to 2nd gear, and its a hard shift. it will not shift into 4th gear. i revved up to 3700rpm in 3rd gear on the highway and no shift.
i replaced both of the speed sensors in the back on the transfer case with the ones from my old transfer case, and no change.

i read on a thread that a guys messed up some of the VSS plugs and had the same issue. but i dont think i did.

another side note: the 2 plugs at the shifts cable module there on the left side on the tranny........ those were a bit corroded. we soldered 2 wires. they were also hard to remove from the old tranny, and hard to push into the new tranny. but they are pushed in far enough i believe. anyone know if an issue here could affect the speedo? or shifting? my guess is no.

tech2

the speedo needs the vss signal for obvious reasons...the trans needs to know load and vehicle speed for proper shifting. both problems are related to the p0502. find a p0502 diagnostic. the low code is usually set for a short...ohm the speed sensor.

when you get it resolved...have someone reset the transmission adaptive learning. Its damaging to a replacement trans to follow the shift adapts of a slipping/blown trans.

tonyvisone

a short huh? i have already replaced speed sensor with the previously used one that worked on my truck.

a buddy helping me didnt have any dielectric grease, but convinced me hes never had an issue using regular grease in plugs. i wonder if this is part of the issue? i wanted to have something in there to avoid any future corrosion issues.

tech2

i had a look at the testing. the code is for low vss signal output.
disconnect the connector at the sensor and check the ohms across the sensor pins. it should be 976 to 2354 ohms for a 4wd.
if that is ok put you meter on ac volts and rotate the driveshaft as fast as you can by hand. the reading should be 0.5v or higher.
if that is good...you need to ohm check the wiring from the pcm to the vss connector.
if you are not getting ac output at your meter...something may be bad in the tcase...output reluctor?

kevinkpk

Low voltage on these things (magnetic speed pickup) is a couple thins, either weak magnet, or the tip is not close enough to the gear it is reading. I don't know of anyway to move the probe closer, but the magnet should be able to pick a small pile of screws.

tonyvisone

i swapped both rear sensors in the new-to-me transfer case with the ones from the transfer case i removed from the truck. this case was working great and not blown up. those sensors are what i am calling "known good" sensors. those are in the truck now and i still have the issue.

tech2- when you say "i need to ohm check the wiring from the pcm to the vss connector.", is the PCM up under the hood? or do u mean the box by the shifter cable?
sorry for the dumb question. i am very versed in my powersports- jet skis etc. i just work on my truck enough to keep her running.

that shifter cable box, like i said has 2 questionable plugs. i am going to replace them soon.

tonyvisone

hi again guys... i got another day on the lift and it didnt go as planned.

as i stated, i swapped both rear trans case sensors to the ones from the case i removed. those were working just fine.

the only other thing that really jumped out when swapping the tranny was that the 2 plugs going into the nuetral safety switch werent up to par. they didnt plug in all the way, some wires were repaired, and some wires a bit corroded.
so i found an old harness in my shed, from the last time i swapped the tranny. (it was on one i bought... harness has never been swapped in my truck).
i soldered and shrunk wrapped all the wires of both of those plugs in.
then the truck wouldnt start. i tried the spare nuetral safety switch too. no start no click.
i verified the wires i soldered like 10 times. finally i tried starting it with the bottom (white) plug disconnected. it fired up. after that i plugged that plug back in and never had an issue. its started every time.

but of course, still no speedo.
i then yanked the old harness apart to trade where the speedo sensor wires go. (sensor on back of trans case, drivers side). they go straight up over the top on the trans up under the engine cover, then to the fuse box. they are green with black stripe, and purple with white stripe....... they are the only 2 wires twisted together by the fuse box.
thinking a wire broke near the tranny somewhere from working, i made jumper wires and connected from the rear tranny sensor up to those 2 wires by the fuse box. still no speedo.

im kind of at a loss here.
i still havent tested the sensor, but id find it hard to believe that both sets of sensors are no good. and i wanted to repair the things i deemed suspect either way.

is there a fuse anywhere for the speedo? or anything that couldve got burnt up in the computer or something?

tonyvisone

hey again guys.
i fixed this a few weeks ago and figured id close the thread out.

i had a hunch there was a wire break between the speedo sensor and top of the motor area. so i had tee'd new green/purple wires in up between the motor and fuse box area. i ran them straight to the speedo sensor. but it still didnt work. then i had an epiphany and pulled over to the side of the road. i cut the old wires right up after the "tee". no i had removed the suspected broken wires from the system. hopped back in the truck and the speedo worked and the truck shifted great!

Roy Wagner

The plugs on the neutral safety switch are in there with a glue. Use a heat gun to soften the adhesive to remove the plugs.
The plugs may have that adhesive jammed in the connector holes. The adhesive is there to seal the plug from the elements.

If you don't remove the plug using a heat gun, chunks of adhesive may be left in there. Only to be jammed into your harness when you go to plug it back in.

Just a thought. Maybe plugin and unplugging the connector finally got the obstruction cleared.

ohtwoZ

Having the same problem but don't have nothing to go off of as far as the wiring goes. wires from the sensor to my pcm are good and don't see anything under the dash.