2004 silverado issues

**ericevans14** · 08-01-2009, 12:20 AM

I have a 2004 silverado 2500 with the 6.0l v8 with 148000 ecently has started to not crank when you turn the key you can start the truck by bypassing the relay the blower motor is also not working and the trans wont shift out of first. i have had it to the dealership twice and the truck wil start fine and drive ok here for a little while and then the problems will all arise again the abs warning light is on and the service brake system is on and it is throwing the code shift solenoidmalfunction and tcc pressure i figured it must be the pcm so i replaced the pcm and the blower motor worked all warning lights were out and it cranked perfectly until i programed the pass lock to unlock the fuel pump and now its back to the same old thing does anybody have any idea what it could be?

**Jimmiee** · 08-01-2009, 10:25 AM

I'm betting all these problems happen when the voltage drops below the threshold. The pcm is programmed to set codes when the voltage drops below 12 volts. I would start with cleaning the battery cables and testing the battery. The base voltage has to be above 12.4 volts after the headlights are on for 30 seconds. Without running the headlights for 30 seconds you will not see true battery base voltage as a surface charge builds up while the truck sits idle. This is where I would start then report the results.

**bill190** · 08-01-2009, 12:33 PM

Yes I would start by monitoring the voltages INSIDE the vehicle. This is where a lot of different computer modules are.

Perhaps you could rig up a multimeter to measure voltage at the cigarette lighter. See what the voltage is there when this problem occurs.

You don't know for sure what the problem is until you do a bit of testing, but there could be a loose main electrical connection somewhere. This would include main ground wires and be sure the battery terminals are clean and snug.

You might try starting the vehicle and "wiggling" main wires. See if you can cause the problem to happen.

There is a LOT more to it that just this, but this is a good first step. That is to be sure all those electronic modules have a good 12 volts getting to them at all times.

Don't keep the multimeter in the car on hot days as the heat can wreck it.

How to use a multimeter...
http://www.google.com/search?hl=en&s...imeter&aqi=g10

You might want to get a plug to plug into the cigarette lighter, then connect the multimeter to the wires with alligator clip test leads like this...

**Jimmiee** · 08-01-2009, 01:24 PM

Bill,

I beg to differ with you about checking the voltages inside the vehicle. You have to start with the source. If the lake is empty there's no use fooling around with the water faucet. <G>

Jim

**ericevans14** · 08-01-2009, 01:39 PM

The terminals are clean and voltage looks good from the gauge but i will check with a meter this is a fleet vehicle so its been maintained mechanically atleast i just dont understand why the compuer solved all the issues unti
until the passlock unlocked the fuel pump then it was back to not cranking

**Jimmiee** · 08-01-2009, 01:52 PM

I believe you have an intermittent voltage problem. Check the voltage at the battery and go from there. I don't understand what you mean by passlock unlocking the fuel pump. Never heard that before?

**ericevans14** · 08-01-2009, 02:19 PM

Passlock is what you do to teach the computer the motor you turn the key on and attempt to start will crank but not fire you let it sit for 10 minutes on run then turn key completly off for 5 seconds and then repeat for a total of 3 times passlock is the dashlight that looks like a car with a lock going through it

**bill190** · 08-01-2009, 02:39 PM

Originally Posted by Jimmiee

Bill,

I beg to differ with you about checking the voltages inside the vehicle. You have to start with the source. If the lake is empty there's no use fooling around with the water faucet. <G>

Jim

I was thinking that since the starter had enough power to start, that power would be good there and the problem would be somewhere past that point.

But yes, good point. Start with the basics!

**Jimmiee** · 08-01-2009, 03:59 PM

Originally Posted by bill190

I was thinking that since the starter had enough power to start, that power would be good there and the problem would be somewhere past that point.

But yes, good point. Start with the basics!

I have seen plenty of false codes caused by dirty battery cables. The codes set during the cranking just before the engine fires up. The battery voltage will drop enough to set the codes and the engine then starts and everything seems fine except the check engine light comes on. You can sure waste a bunch of time troubleshooting these codes because there's not really a problem in the circuit.