01 Silverado backup lites

I've checked the backup lite fuse, all are good. Checked bulbs and they are good. I was told there is a switch some where on my allison tranny. I could use some help.

I've checked the backup lite fuse, all are good. Checked bulbs and they are good. I was told there is a switch some where on my allison tranny. I could use some help.


What size truck and HD or regular and 4 or 2 wheel?
Get a good test light or volt meter and wiring diagram.
First test for voltage to backup light socked and for ground..
If none then check for voltage to and threw both backup light fuses.
If voltage to and threw one and none to other it is not going threw backup light switch.
Go to backup switch and see if backup light voltage to and threw it.

The first backup light fuse feeds backup light switch on transmission and scond fuse is between switch and backup lights.

I have a 2001 Silverado w/8.1L and allison tranny. I have voltage present at the B/U LP fuse but I don't know the wiring color code to (as the garage says) the NSBU switch. Can't find a wiring diagram in the local parts stores. The Veh B/U and TRL B/U fuses are good but no voltage. That is with the tranny in reverse and ign sw on.

More info: I jumpered 12V to fuse going to backup lites. That part of the b/u lite ckt is ok.
b/u lites came on.

More info: I jumpered 12V to fuse going to backup lites. That part of the b/u lite ckt is ok.
b/u lites came on.

There is 5 Silverado 1500-1500 HD. -2500- 2500HD and 3500 and then 2 0r 4WHEEL DRIVES AND THEN AT OR STD. transmissions AND THE WITH TRAILER LIGHT WIRING AND WTHOUT TRALER LIGHT WIRING.

Tell us what one you have and we can give you the wiring colors
Or.
A all Data on line DIY subscription will give you the wiring diagram.

You need to check for 12 volts on the fuse going to back up light switch and the for 12 volts out of switch to back up light fuse to backup lights.

If you jumped the fuse to backup light aaND LIGHTS CAME ON THEN YOU AR NOT GETTING VOLTAGE TO BACKUP LIGHT SWITCH OR THREW IT.

Get a wiring diagram and fire up the test light and see where you are losing voltage.

I have a 2001 Silverado w/8.1L and allison tranny. I have voltage present at the B/U LP fuse but I don't know the wiring color code to (as the garage says) the NSBU switch. Can't find a wiring diagram in the local parts stores. The Veh B/U and TRL B/U fuses are good but no voltage. That is with the tranny in reverse and ign sw on.

You said.
The Veh B/U and TRL B/U fuses are good but no voltage. That is with the tranny in reverse and ign sw on.[/QUOTE]

No voltage at either one right?

I've checked the backup lite fuse, all are good. Checked bulbs and they are good. I was told there is a switch some where on my allison tranny. I could use some help.

the power is supplied to the park / neutral switch at all times. when you place into reverse a switch in this assy puts this 12 volts to the back up fuse which feeds the back up lights. this switch should be on the drivers side of the transmission in the area of the position selector . you will see wires to/from it . the light green wire should be the feed to the back up fuse.

good luck !

MT-2500 and jCat I want to thank you both for trying to help me out of this problem.

MT-2500 wanted more info on the vehicle. It's a 2001 Silverado 2500HD long bed with an
8.1L engine and the 1000 allison transmission. I might add the allison was replaced with
a reman allison 2009.

jCat I'm trying to recapture what has gone down so far. The b/u light cir is as follows:
12V from battery to B/U LP fuse (25A) to the switch on the side of the tranny. With the sw closed (gear shift lever in reverse, key on) the 12V is brought back to the VEH B/U fuse (15Amp) and TRL B/U fuse (10A) then on to the back up lights. I have 12V on the B/U LP fuse but none on the VEH B/U fuse with gear shift in reverse and key on. So far I'v been able to isolate the b/u lites as not being the problem by jumpering 12V to VEH B/U fuse socket and b/u lites worked fine. Now I'm back to the b/u lite switch. So far I'm of the impression it part of the NSBU which has two connectors. If this is correct I need the color code of the b/u 12v going in via the 25A fuse and out to the 15A fuse. I'm sorry about the long drawn out writing but it's the only way this 74 yr old head can get it sorted out, on paper.

Again thank you two for bearing with me.

MT-2500 and jCat I want to thank you both for trying to help me out of this problem.

MT-2500 wanted more info on the vehicle. It's a 2001 Silverado 2500HD long bed with an
8.1L engine and the 1000 allison transmission. I might add the allison was replaced with
a reman allison 2009.

jCat I'm trying to recapture what has gone down so far. The b/u light cir is as follows:
12V from battery to B/U LP fuse (25A) to the switch on the side of the tranny. With the sw closed (gear shift lever in reverse, key on) the 12V is brought back to the VEH B/U fuse (15Amp) and TRL B/U fuse (10A) then on to the back up lights. I have 12V on the B/U LP fuse but none on the VEH B/U fuse with gear shift in reverse and key on. So far I'v been able to isolate the b/u lites as not being the problem by jumpering 12V to VEH B/U fuse socket and b/u lites worked fine. Now I'm back to the b/u lite switch. So far I'm of the impression it part of the NSBU which has two connectors. If this is correct I need the color code of the b/u 12v going in via the 25A fuse and out to the 15A fuse. I'm sorry about the long drawn out writing but it's the only way this 74 yr old head can get it sorted out, on paper.

Again thank you two for bearing with me.

with the transmission replacing I now understand why this is a problem . at the transmission the light green at the switch goes to the back up light fuse. since this is a 2009 tranny well I do not have that info on where the switch would be but on the 2001 it should be on the tranny left side by the shifter and this is where these wires that supply the 12 volts to the transmission would be. still with what you have just stated it appears the switch is the problem or the wire at this switch got damaged/spliced bad /connected half azzed etc...


getting old sucks .

Thanks again for the response jCat. The NEUTRAL SAFETY BACKUP switch is mounted on the drivers side of the tranny. The switch is tan in color. I was laying under the truck today trying to stare the sw down. Didnt do any good. The lower connector has two wires
easily seen. One is light green the other pink. Would these be the two wires I'm looking for?

Tomorrow I going to dive under there again, pull the connecter and fluke it out. Let you know what I find.

Thanks again for the response jCat. The NEUTRAL SAFETY BACKUP switch is mounted on the drivers side of the tranny. The switch is tan in color. I was laying under the truck today trying to stare the sw down. Didnt do any good. The lower connector has two wires
easily seen. One is light green the other pink. Would these be the two wires I'm looking for?


the light green should be the wire .

I would apply power to the backup light fuse then see if the light green wire under the vehicle at the tranny has power with the jumper and the lights on and then remove the jumper and now no voltage lights / off . now you know that is the correct wire.

measure the pink wire that should always have 12volts to it with the key off or on.

jCat, thanks again for the info. I will do what you suggested but probably not till friday.
This mid 90 to 100 degree temp is doing a pretty good job of keeping me out of the garage.
My tranny has been in and out the truck 4 times now. They keep installing bad reman. transmission. Thats why I'm concerned about wiring and or jammed connector before I spend the money for a new switch.

Well jcAT I made it back. Used a hair dryer on the NSBU switch. Got the connectors as hot as the hair dryer would get them and they came right out. Wouldn't recommend a heat guns. Possibly melt wire insulation or connectors. Found the backup lite circuit was routed through the seven pin connector pin c (input from the 25A fuse) PINK wire. Out put to the tail lite fuse was on pin F (output tail lite fuse 15A) LT GRN wire. Jumpered the two together and had tail lites. Bad NSBU switch?? Replaced the NSBU sw. (Got the connectors real hot again and they slid right in. Don't know what kind of glue they used on the connectors, almost like hot glue. Backup lites work fine. Dismanttled the old switch and found when they last replaced the tranny they apparently didn't heat up the switch pins and connector before installing the connectors and jamed in F. It wasn't making connection. Guess everone screws up on occassion. Thaks again jcAT and MT-2500.

Well jcAT I made it back. Used a hair dryer on the NSBU switch. Got the connectors as hot as the hair dryer would get them and they came right out. Wouldn't recommend a heat guns. Possibly melt wire insulation or connectors. Found the backup lite circuit was routed through the seven pin connector pin c (input from the 25A fuse) PINK wire. Out put to the tail lite fuse was on pin F (output tail lite fuse 15A) LT GRN wire. Jumpered the two together and had tail lites. Bad NSBU switch?? Replaced the NSBU sw. (Got the connectors real hot again and they slid right in. Don't know what kind of glue they used on the connectors, almost like hot glue. Backup lites work fine. Dismanttled the old switch and found when they last replaced the tranny they apparently didn't heat up the switch pins and connector before installing the connectors and jamed in F. It wasn't making connection. Guess everone screws up on occassion. Thaks again jcAT and MT-2500.

I want to thank you for that heat tip on removal of the connector . with all that tranny work this is gonna happen. good work on the fix .

you did save quite a bit on this repair ..