after a unsuccessful visit to best buy my truck started doing strange things like all of a sudden the trans. would only use second and third,the tach. speedometer and shift indicater light stoped working.the next day things back to normal , that same day it acted up again.best buy was to install remote starter but did not,needed more parts .coincidence ,not sure.can anyone help,THANKS.

Did they actually touch or alter any wiring harnesses?

Scan the vehicle for codes?

the tech said he did not touch anything, the codes are p0740,p0753,p0758,p0785,p1860.THANKS FOR ASKING!!!!!!

Sure sounds like this:

Technical Service Bulletins - Automatic Transmission Stuck in 2nd/3rd Gear/MIL ON/DTC'*

Bulletin No.: 01-07-30-002E
Date: September 23, 2005


TECHNICAL
Subject:
Malfunction Indicator Lamp (MIL) On, Transmission Stuck in Second or Third Gear, Instrument Cluster Inoperative (Verify and Repair Source of Voltage Loss In Transmission Solenoid Power Supply Circuit) Models:
2006 and Prior GM Passenger Cars and Light Duty Trucks
2005-2006 HUMMER H2
2006 HUMMER H3
2005-2006 Saab 9-7X with 4L60-E, 4L65-E, 4L80-E or 4L85-E Automatic Transmission (RPOs M30, M32, M33, MT1, MN


This bulletin is being revised to update model years, add additional models and add additional diagnostic information. Please discard Corporate Bulletin Number 01-07-30-002D (Section 07 - Transmission/Transaxle).

Condition
Some customers may comment on one or more of the following conditions:
The Malfunction Indicator Lamp (MIL) is ON.
The transmission is defaulted to second gear (4L80/85-E).
The transmission is defaulted to third gear (4L60/65-E).
The instrument cluster is inoperative. Upon investigation, one or all of the diagnostic trouble codes (DTCs) P0740, P0753, P0758, P0785, P0787, P0973, P0976, P1860, P2761, P2764 and P2769 may be set depending on the vehicle.

Cause
The most likely cause of this condition may be a loss of voltage to the transmission solenoid power supply circuit. This condition may also be the result of an incorrect installation of an aftermarket electronic device such as a remote starter or alarm system.

Correction
Important: If the vehicle is equipped with an aftermarket electronic device and the DTCs are being set when the device is being used, verify that the appropriate fuse is being supplied battery voltage during operation. If voltage is not present at this fuse, these DTCs will be set due to lack of voltage at the solenoids. This condition is most likely to occur with an incorrectly installed remote starting system. If this is the case, refer the customer to the installer of the system for corrections. ANY REPAIRS DUE TO AFTERMARKET INSTALLATION OF ACCESSORIES IS A NON-WARRANTABLE ITEM.
1. With the ignition switch in the RUN position, test for battery voltage at the circuit fuse in the transmission solenoid power supply circuit. Refer to the appropriate SI Document for the transmission solenoid power supply circuit information.
2. If battery voltage is present at the fuse, inspect the ignition voltage circuit between the fuse and the transmission for possible opens.
3. If battery voltage is not present at the fuse, test for continuity between the fuse and the ignition switch. If NO continuity is between the fuse and the ignition switch, repair the open in that circuit.
4. If you have continuity between the fuse and the ignition switch, the most likely cause is the ignition switch. Replace the ignition switch using the appropriate Ignition Switch Replacement procedure in SI. Refer to group number 2.188 of the parts catalog for part description and usage of the ignition switch.
__________________

sure does sound like it,will need to do some testing,the truck has 270k,maybe ignition,maybe not best buy tech,florida truck,very very clean for 98 but alot of miles.any idea where to go first,THANKS.

Yes, a lot of miles, but unless you are a big believer in coincidences I would pay particular attention to the TSB that Tech II has so kindly posted for you especially the part about remote starters. I'd bet you dollars to donuts the Best Buy "tech" lied to you about not touching anything, think about it, how long did they have your vehicle before they claimed they didn't have the parts? They should have known that right out of the gate when they saw or you advised them what vehicle you had.

2004 Bonne SLE
1971 Chevelle SS

truck will be here tommorow for testing,have to find trans. solenoid fuse to start,under dash inspection all appeared o.k. THANK YOU MEMBERS FOR YOUR HELP,will keep you all posted on results. ? trans fuse location.

further testing i found only 3.3volts at the trans. fuse ,i then temp. put 12v to the fuse and things all better,?ignition switch,any suggestions,THANKS YOU ALL!!!!!!

Follow test in TSB....

best buy revisit tommorrow.we will see what happens with that ,then test,THANKS.