05 silverado 6.6 urgent help

[AFadhel]

hi
i am a new member , i have had many issues with my silverado for the past 2 months , i finally decided to change the batteries as the batteries that were on might have been the problem for my p0700,p0500 cods . the truck had 2 ac delco batteries 78a72 CCA 650 was told that wernt enough . so today i disconnected booth batteries and after 5 hrs installed new optima 78/34 batteries but the car wouldn't start , it will crank but not start with a new light on the dashboard that indicates the glow plug . thought the new batteries were to blame , returned the ac delcos still wont start just crank any advice on what of might happened and how to resolve it ?? unfortunately i am not in the USA and the dealer dosnt sell or handle diesel trucks here as my truck was a special import .. please any one help .. willing to phone anyone for a live instructions i will take care of the oversees call charges .

[Kennedy]

I'm not sure what to say, but I have heard from callers that after a battery change the ECM was dead. No rhyme or reason to it. I speculate that maybe some are getting arced out somehow? I would first look to see if there are any trouble codes and see if the ECM is communicating with the scan tool.

Also try this:

Key on attempt to start. Important-do not turn off after cranking. When engine fails to start leave key on 10 minutes.

Turn key off for 30 seconds. Repeat 3 full cycles if necessary.

It could be that the anti theft signal somehow got lost. The above procedure should remedy this.

[AFadhel]

thanks for the reply .. cant connect the scan tool obd wont link .. ithink it needs to start the engine first ... new thing i noticed the EDU relay was hot when touched....

[Kennedy]

With key in run position the ECM should communicate normally.

If the code reader does not power up then a fuse is blown.

Also a good idea to check the ECM fuse etc in the underhood panel.

Curious, when you disconnected both batteries did you do both negatives first? This standard procedure seems to be getting lost these days and a lot of my calls are from guys with toasted ECM's and TCM's that got arced out by a live positive cable floating around.

[More Power]

John is correct. The negative terminals of both batteries must be the first to be disconnected when doing battery service, and the negative terminals must be the last to be re-connected when completing the battery service. Expect a relatively small amount of arcing to occur when re-connecting the negative battery terminals (kinda disturbing when you first experience this, but it is harmless).

Not doing this can create a situation where a live/hot battery cable end could make contact with the metal case of a computer (ECM/TCM) module. According to GM, the usual result from this mistake is for one of the black ground wires (pretty small) in the ECM/TCM connector bundle to burn out. So... check the wiring harness that connects to each of these modules, looking for burned wiring. You will have to examine the wiring that connects to the module and all the way to the underhood electrical center (a couple of feet of wiring). If you locate a burned wire, you (or someone else with the expertise) can replace that wire. If you're lucky, this could solve the problem.

In addition, check all fuses, both in the underhood electrical center and the fuse block on the driver's side end of the dash.

Good luck...

Jim

[Kennedy]

One thing that I will add is that I have had guys attach a ground wire from the ECM or TCM case to ground and it did run after doing this.

The cautionary note is that this is NOT a permanent fix and will almost undoubtedly bite you in the ass when you least expect it as this typically fails down the road.