2001 Chevrolet Truck

Electrical problem
2001 Chevy Truck V8 Two Wheel Drive Automatic 106000 miles

2001 Chevy 2500 HD 6.0 liter. Battery will go dead after sitting for 2 + days. Battery will charge and engine will start. Engine cranks slow if sits over night, engine will start and run or acellerator needed to keep running at 1,000 rpm for about 1 minute and idle and drive fine. Tow /haul will come on and not turn off at start up or Tow/haul will not activate at all as well. Battery is 1 month old, speced to the vehile. Alternator has been tested and ok, puts out 14.65 volts at start up. All positive and negative connections at the battery, engine, starter, fuse center under the hood, chasis and all other found ground and positive connections have been cleaned and tight. All fuses have checked with meter and all good. AT No Time does the CHECK ENGINE LIGHT come on.
I can drive the truck for a day (10-200 miles) and have no issues at start up or it will crank over slow, start and run fine but in tow/haul or not in tow/haul. Tow Haul mode will not work, it will only only activate at start uip on it's own at times and It will not turn off.
Any suggestions? All I have heard from people is the computer, Chevy dealers say it is not and want 90-100 dollars an hour to diagnose, and we all know how much that will eventually cost.
FYI I am a marine diesel technician for the past 15 years, 9-1100 hp range, mechanicle and common rail fuel systems, not an auto mechanic so I am at al little bit of a disadvantage when it comes to vehicles.
Best regards, Roger

updated 12/1/09
No, I do not have On Star. I also do not have a beacon switch as a dealer suggested.
This will happen with all equipment turned off, radio, fan, etc. I have not used the factory security and it still happens.
I have no after market add ons/ up grades installed. The truck is the same as the day I purchased it new in 2001, stock. Thanks, any other questions, please ask. Roger
Roger Sherman
November 28, 2009.

I can try to help you with your issue, but you are going to have to be patient, I am going to have to turn into Dr. House. I only have one question for you, does your truck have On-Star and is it activated?

Dr Loot
Nov 29, 2009.
No, I do not have On Star.
I do not have any aftermarket accessories installled either, meaning no : stereo system, plow hook up or plow, beacon lights or flasher system, alarm system ( factory installed ), remote start, ect.

Roger Sherman
Dec 5, 2009.
It sounds like you have a circuit in the vehicle that is taking a draw. The way to check that is to remove one of your battery cables, it doesn't matter which one take a test light and put one end on the battery cable and the other end of the battery with everything turned off and the doors closed. If the light stays on (the test light), then you have a circuit that is drawing power. Open up your door, make sure the interior light does not come on if it does take your finger and push the button in on the door and hold it or remove the light bulb, after you have done that, begin to remove your fuses, from the dash one by one and putting them back checking the test light as you remove the fuse and if the test light goes out, that's where your problem is, in that circuit.
Also Iam sending you a diagram of the trans, so you can check out the tow/haul.

Dr Loot
Dec 5, 2009.
Thanks for the advise.
Performedyour suggestion with test light and cable removal. Results no draw found, test light never lit up. I rechecked at night to see if test light was dim and hard to see during the day and no draw.

Load tested the battery, was good, replaced it with a new one anyway. Slow crank, no or hard start, no changes.

Removed the starter, rebuilt it completely, new soleniod, hardware for connections, checked the windings, replaced the brusch assy, tested ok, reinstalled no change.

Checked the alternator again, tested at local electrical shop tested fine, traded it in for a rebuilt on the shelf anyway, installled it, no change.

Replaced the main battery cable to the fuse block and to the starter even though the voltage checks at the battery and starter were within.02 of each other static and 1.0 volts at crancking, no change.

Replaced the ground cable to the block, no change.

No draw found at any time after all work performed by step of each change.
Any other suggestions?

Thanks, Roger

Roger Sherman
Jan 2, 2010.
Sorry Roger I have one more question, did you shim the starter? The starter may be binding due to insufficient clearance. Start with a.020 shim and check the clearance with a wire guage or listen to the starter to make sure it coasts after disengagement.

Dr Loot
Feb 22, 2010.