The Rpm on my LS swap (04 5.3) is dropping crazy when I when am coming to a stop or slowing down.
At time it drop so low the engine would die.
This started just last week.

 

Does your engine also have an extended cranking time as compared to original? If yes, I predict that your PCM has lost its "memory keep alive power" wire. This helps the PCM to retain a few learned parameters such as what it takes to establish and hold a good idle.

Rick

 

Vac leak frrom a rotted hose would do the same, check some stuff under the hood.

 

what do you mean by extended cranking time? I usually have to crank it twice before it start.
where is this memory keep alive power wire?

 

No vac leak, but will check again

 

Hello,

Do you have a PCM with a red and blue set of connectors? Or blue and green? My suspicion is blue / green. If yes:

Blue connector, pin 20, an orange wire. Should have 12 volts all the time. Even during cranking.

Blue connector, pin 57, another orange wire. The same. Twelve volts all the time.

There are no twelve-volt memory wires on the green connector.

2004 Vortec PCM Pinouts

Rick

 

I do have the blue and green connectors. I will check those wires.

 

I am reading 12v on both 20 and 57 wires

 

Actually am reading about 10.5v when cranking.

 

That is a quite low battery voltage when cranking. Most of the tuning people mention not going below about 12.0 volts at any time. Where are you measuring that 10.1 volts value? What is the source of power for pin 20 and pin 57?

Rick

 

Red voltage meter lead to pin 20/57, black lead to battery negative.

 

Not sure if this is related, but after doing that 12v check on those two wires, 20 and 57 at blue connector, I started to get code P0200, and truck runs bad. Checked the fuse box and found a melted injector fuse. Replaced it, seing 12v at that fuse, but P0200 won't go away.

 

You've got a wire shorted to ground.

Is this an aftermarket wiring harness, and if so, which brand is it?

 

Weird how this just happen right after testing pin 20 and 57 above.

Its an aftermarket harness.

https://highperformanceinjectors.com...RaUIHmw_OoxxlG

 

You need a new Fuse Box that thing is wasted. Whenever you see that you don't put a new Fuse in, that's melted because the wire is grounded out, as mentioned.

Whatever Bank that is, that power wire from that Fuse is pinched in something and now it's grounded out. Since the problem started recently that's what I'm thinking.

Time to strip wiring down and find the problem.

You get what you pay for when you buy that cheap bullshit. Saves you $50 so you can buy a fire extinguisher when it smokes the car.

 

I check continuity between injectors pink wires and pink wire at the fuse box, nothing on both banks
Checked 12v at the injectors, nothing. Checked continuity between pink wire at the main connector on each bank to the pink wire at fuse box, it checks out good and this is on both bank.

 

So you have 12V on the Coils but not the Injectors if I'm reading that right?

 

That's correct.

 

Well that Harness is not made to what GM did with theirs, as we said there's a wire grounded out somewhere that shouldn't be.

You need to find that wire and a new Fuse holder.

Buy cheap low quality **** that's what happens.

 

"You get what you pay for when you buy that cheap bullshit. Saves you $50 so you can buy a fire extinguisher when it smokes the car."
We have a winnah!!