PCM swap

Good morning,

It must be the exact number of the one you are replacing and you have about a 50-50 chance of it taking the program. Sometimes it works fine and other times it does not.

Roy

It used to work with previous program levels of the diagnostic software, but the last time that I tried doing a PCM swap it didn't work, but some techs keep their own laptops with older versions that might work.

What would you recommend I do?

If you need an ECM, I would get a new one and have it flashed to your VIN.

What makes you think you need an ECM?

Roy

Because when I got the truck the idle would go up and down randomly and I would be driving it and all the sudden it would lose power and then kick back in randomly. Then a couple of months later one day it started running rough and it didn't have any power at all a week. After that I was going down the road and the truck shut off and wouldn't start back up. It would turn over but not even try to start. I plug a code scanner up to it and it just says error. The day after it broke down the battery was dead and it was a new battery. Oh, and it seemed like it took a long time to shift gears.

Okay, got it.

That would be an expensive guess if you are wrong.

https://www.2carpros.com/articles/engine-has-low-power-output

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Does it run at this present time?

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Roy

No, it will turn over but wont even try to start.

Okay, you need fuel pressure, spark and compression.

https://www.2carpros.com/articles/car-cranks-but-wont-start

Can you hear the fuel pump run with the key on?

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

When you crank the engine, does it show RPM on the tachometer on the dash? That will tell me if the crank sensor is working.

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Compression would be last.

https://www.2carpros.com/articles/how-to-test-engine-compression

Roy

No, the rpm doesn't move at all. When I turn the key on I hear 2 clicks under the dash it sounds like something is trying to turn on but then it turns back off.

And no I don't hear the fuel pump come on when I turn the key on. I have already changed the fuel pump and filter, because I thought it was going out.

Okay, we need to do some testing. Do you have a voltmeter and a test light?

https://www.2carpros.com/articles/how-to-check-wiring

We need to check some powers at the power relay and the fuel pump relay.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Roy

Yes sir, I have both a voltmeter and a test light, but i'm at work right now I get off at 5:00 so I will be home around 6:30. Can we continue this diagnostic test when I get home?

Tonight will be fine.

Roy

Okay, thank you so much. You don't know how much I appreciate this.

Pop the hood and on the driver side, open the fuse box cover and give this relay a tap. If it starts or stalls when you tap it, try swapping it with it's neighbor. Very very very common!

As he said, that is the power relay that controls all power to the fuel pump relay and a lot of other components that I highlighted in the diagrams I sent you.

Roy

Okay, so I checked all my fuses and I found a couple of them that were blown so I replaced them and my truck started and stayed running but it still has no power. It idles when I have it in park just fine but once I put it in gear it it idles real low and tries to shut off. When i'm driving the engine runs rough like it has a couple of cylinders misfiring and when I give it gas it acts like it has a vacuum leak. I have to barely touch the gas pedal little by little and let it build up speed it takes me about 1 1/2 miles to get up to 35 mph.

Okay, you need to go back to my original suggestions and check the fuel pressure. That is the start.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

https://www.2carpros.com/articles/engine-has-low-power-output

I also suspect the exhaust is clogged from cat converters. You could get a back pressure gauge or you could loosen the head pipes from the manifolds and then drive the truck and see if power returns.

Roy

It's not the catalytic converters. I got some off another truck and swap them out and still the same problem. I found a plug towards the back of the motor on top that is not plugged into anything not sure what it's for. I was wondering if maybe you knew.

Can you post a picture for me of the plug?

Also, did you check the compression in a cylinder or 2 to see if the valve timing jumped?

I would not rule out the exhaust. I would drop the front pipes and start it and drive to be sure the rest of the system is not restricted.

Roy