1999 gmc jimmy diagnostic tool hook up wont work

If it is like my 98 Silverado it is replaced with some degree of difficulty. I watched a video on you tube.

Maybe the brushes is worn out ,and you need to replace a new one

may be you should make a diagnostic and you can do it in a garage but if you want to do it by yourself you could buy a diagnostic tool here: spobd2.com

With the emergency - parking brake set ? Anytime the vehicle is running an the parking brake is off the daytime running lamps come on . That or the sensor on top of the dash is bad , or the DRL relay is bad or the BCM - body control module . Could have DTC'S - diagnostic trouble code's stored . Hooking up a factory or professional scanner would make diagnosing this easy . Do you know what wiring diagrams are ? How to use a DMM - digital multi-meter to test electrical circuits ? Free wiring diagrams here http://www.bbbind.com/free_tsb.html
Enter vehicle info. year , make , model an engine . Under system click on lighting then under subsystem click on daytime running lamps . Click the search button then the blue links .

some of these had an ALDL fuse in the fuse panel.check all fuses with a test light.it could be that the ALDL connector is not being fed by the computer also in which case you will have to check powers and grounds at the connector with a volt meter,or the computer has a problem sending to the connector.another problem that some times happens is the diag tool info not entered correctly of wrong chip/card in the tool.just some things that it could be.

The best way to know what is happening there is to drive a GMC dealer and get them to hook in the diagnostic tool and read the computer memory for present faults.
Cheers

this is caused by the reverse clutch pack being worn out. You will need the trans pan removed and a diagnostic run.

When you hook the pressure test guage to shrader valve on fuel rail what it reads is what the pressure is from pump, around 60 p.s.i. all you need to do is hook up the guage and turn on key, you do not have to turn engine over, and if pump is good it will shoot up to 58 or 60 right now.

Service the throttle body system, and injectors.

then remove the negative battery pole, press the brake down for 90 seconds reconnect the battery pole..

Did air charge sensor get unpluged at one time with key on?