Gear indicator not working

[mrjean]

had to change rear axle assembly and transmission (from two different trucks). when i picked it up the gear indicator was working, but now it just randomly stops working and then working again. P R D 3 2 1 are always there in green, but the small line underneath works randomly.

the other day i had it in reverse but the gear indicator was not showing anything and the reverse lights were not on either. other days i reverse and the indicator is on and the lights are on.

what could it be?

 

[The_Roadie]

There is a switch assembly on the side of the tranny where the cable moves the lever. This is usually the problem, or a pinched wiring harness or flaky/broken wires going from the switch to the PCM.

Item #12.

View attachment 32588

 

[mrjean]

can the switch assembly go bad? i hope they still have my old tranny over there...(if it goes mounted with the tranny)

 

[The_Roadie]

can the switch assembly go bad?

ANYTHING can go bad, but as I mentioned, it may be the wiring. It has to be troubleshot or shotgunned or simply taken out and shot. Three choices. :wootwoot:

 

[Texan]

I think that I read on another thread, that there is a difference between
the 2002 and 2003 and later switch. One has one connector, the other has two.

 

[neelskit]

I started having a similar problem to the OP. Intermittently, the indicator on the dash will not show the shifter in P, N, or D. When this occurs, R, and 1-3 are displayed when shifted. The strange thing is, the truck will not start in D, as it shouldn't. Is the neutral safety switch separate from the indicator switch? Also when this occurs, the door locks do not lock and unlock when shifted out/in to P. I've also had an intermittent REP followed by no start issue that started happening at the same time. When the truck decides to re-start, all is fine. Maybe my TB doesn't like all this below 0 weather we've had this winter...

 

[Texan]

I started having a similar problem to the OP. Intermittently, the indicator on the dash will not show the shifter in P, N, or D. When this occurs, R, and 1-3 are displayed when shifted. The strange thing is, the truck will not start in D, as it shouldn't. Is the neutral safety switch separate from the indicator switch? Also when this occurs, the door locks do not lock and unlock when shifted out/in to P. I've also had an intermittent REP followed by no start issue that started happening at the same time. When the truck decides to re-start, all is fine. Maybe my TB doesn't like all this below 0 weather we've had this winter...

Just random thoughts. If the door locks do not function (lock/unlock) they may not be getting the signal
from the switch on the transmission. I do know from experience that the "weather pack" electrical connectors
under the vehicle can corrode and not make good contact. Solution: contact cleaner and dialectic grease.

 

[IllogicTC]

I started having a similar problem to the OP. Intermittently, the indicator on the dash will not show the shifter in P, N, or D. When this occurs, R, and 1-3 are displayed when shifted. The strange thing is, the truck will not start in D, as it shouldn't. Is the neutral safety switch separate from the indicator switch? Also when this occurs, the door locks do not lock and unlock when shifted out/in to P. I've also had an intermittent REP followed by no start issue that started happening at the same time. When the truck decides to re-start, all is fine. Maybe my TB doesn't like all this below 0 weather we've had this winter...

It appears to me there's two circuits in the park/neutral switch.

The first circuit directly relates to starting. There's a pink wire that runs to the PNP switch, that's the hot for this particular circuit. This circuit will only be closed in Park or Neutral, and the output exits through a light-green wire. Literally the only thing that uses this neutral-safety circuit is for starting, everything else like gear display and locks are run from the second circuit.

The second circuit - a gray, yellow, white, and black/white all run into the PNP switch. Each wire runs to a different switch inside the PNP switch case and I believe are actuated in different combinations to ascertain the current transmission selection, acting like a binary system. There's a black wire that exits the PNP, I believe it should be pin D on connector C2, this is the ground for these switches. The ground wire runs up to the underhood fuse block, then comes back out and grounds to the lower-left side of the engine.

My first guess would be to scope out the ground wire and all four colored wires in this second circuit and make sure it's all good and gravy, and the connectors too. It sounds to me like maybe one or more of the colored wires in this circuit may be damaged. If everything checks out, it may be time for a new PNP unless someone has a different idea. Make sure to check continuity and check the wires themselves as fully as you can. These wires terminate at various pins on the PCM, and the PCM transmits your current selection via the Class 2 Serial bus to the instrument cluster to display. If everything else is good and you've replaced the PNP and it's still doing this, you may have some sort of issue in the serial data lines.

 

[mrjean]

mechanic took a look at it, tinkered with it and it works now. he said it might need to be changed in the future tho. has not messed up since.

 

[IllogicTC]

mechanic took a look at it, tinkered with it and it works now. he said it might need to be changed in the future tho. has not messed up since.

The PNP switch? I'd heed his advice, but at least the interim fix will get you up to the parts store or rambling around town a little while while you get prepared to get it repaired. Thanks for the follow-up

 

[mrjean]

the switch now shows an indicator on all gears except drive. when i push the shifter a bit up or down (on drive) it indicates D. however, now my cruise control does not work. im sure its because its not being registered. any ideas? i know i have to switch it out.

can someone help me out on the official part number from GM?

 

[The_Roadie]

You can locate them on eBay, Amazon, or your local parts store just by description. Rockauto is another great resource to see the array of aftermarket alternatives available and the price ranking.

Added:

OK, here's what Rockauto lists:

ACDELCO Part # D2257C GM 24221125 $44.79
STANDARD MOTOR PRODUCTS Part # NS319

 

[mrjean]

awesomeness...im going to mess with it on saturday. i dont think its the sensor per-se but the actual cable on D. all the other gears are being indicated. dont know why drive is having the issue which im assuming is tripping up the cruise control.

 

[IllogicTC]

awesomeness...im going to mess with it on saturday. i dont think its the sensor per-se but the actual cable on D. all the other gears are being indicated. dont know why drive is having the issue which im assuming is tripping up the cruise control.

I wouldn't entirely hedge my money on it being the cable if only D is affected. Typically a stretched cable would make all of it weird, or more toward one end or the other, not just the one spot in the exact middle. One typical effect is say you're in D, it would show you're in 3, or when you're in 3, it'd say you're in 2.

Yes, this may be tripping cruise control as the PCM is expecting a report on transmission gear selection, and may be under a false assumption that the transmission is in neutral or something. One way to test if the cruise control itself is still good is to set the transmission in 3 (if 3 still lights up correctly) and try setting a speed. If it takes and holds, then cruise control checks out.

My money is on the switch itself. If the switch does not cure the issue, time to go through all the wiring

 

[Texan]

I think that I read on another thread, that there is a difference between
the 2002 and 2003 and later switch. One has one connector, the other has two.

Just a suggestion. You might want to check how many connectors are on your switch.

 

[mrjean]

tomorrow we will check it out. see what comes up with it. if its the switch, i think i saw it new for like 35 bucks or something. also #9, should it be changed as well. its a moving mechanism right?

 

[Texan]

tomorrow we will check it out. see what comes up with it. if its the switch, i think i saw it new for like 35 bucks or something. also #9, should it be changed as well. its a moving mechanism right?

#9 is the shift lever with #10 nut to hold it on to shaft that comes out of transmission.
It should be OK, but note that it is connected to the cable #5 with a ball connection that the socket is
made of plastic and can be fragile because of age and heat. The switch itself can be adjusted
to a degree with the bolts #11. That adjustment might solve your problem.