Very Strange issue 2005 tahoe

[FLORIDA1]

2005 2wd Tahoe with a 4.8.
Issue originally started with colling fans running on there own, change temp switch sensor.
Now when Tahoe running & go to turn A/C fan switch on I hear compressor kick on but then as soon as the fans kick on my engine shakes & then dies.
Turn AC fan switch off, start Tahoe runs great. Turn AC or heat fan switch on Tahoe engine will buck then die.
It's almost as if the fans are causing the issue because it doesn't do it until fans kick on.
Can somebody point me in the right direction, I'm lost with this one.
Thanks alot

 

[wjburken]

2005 2wd Tahoe with a 4.8.
Issue originally started with colling fans running on there own, change temp switch sensor.
Now when Tahoe running & go to turn A/C fan switch on I hear compressor kick on but then as soon as the fans kick on my engine shakes & then dies.
Turn AC fan switch off, start Tahoe runs great. Turn AC or heat fan switch on Tahoe engine will buck then die.
It's almost as if the fans are causing the issue because it doesn't do it until fans kick on.
Can somebody point me in the right direction, I'm lost with this one.
Thanks alot

Might we worth taking the A/C belt off and see what happens. You might have a compressor that’s locking up and stalling your motor. Not sure, but I can see where the fans are kicking on due to the state of your A/C system and is purely coincidental.

 

[Rocket Man]

The fans draw a lot of power. Your alternator may be having a hard time keeping up. If you rev it, does it stay running?

 

[FLORIDA1]

If I Rev it, it just misses and stumbles & throws a CKP code

 

[FLORIDA1]

Runs smooth as long as I don't turn AC on or the fans don't kick on

 

[Rocket Man]

If I Rev it, it just misses and stumbles & throws a CKP code

What is a CKP code? What is the actual code #?

 

[Rocket Man]

Try unplugging the fans, and if nothing changes plug them back in and remove the AC compressor belt to see if anything changes. There’s an electrical connector on the fans themselves you can unplug.

 

[Fless]

You may need to do a crankshaft position variation relearn. Some advanced scanners can do this, for sure a Tech 2 would. Or a new sensor.

As @Rocket Man asked, what's the exact code you're getting?

 

[FLORIDA1]

What is a CKP code? What is the actual code #?

I think it was PO336

 

[Rocket Man]

I think it was PO336

I’m thinking that’s a result of the stumbling, shaking that’s going on. It makes no sense that the crank position sensor is causing the issue if it runs fine until the ac fans come on. If the sensor was the cause, then the truck wouldn’t be running right at all imo. Try what I suggested earlier and let us know.

 

[Fless]

See the OP's other thread for the diag. https://www.tahoeyukonforum.com/threads/2005-2wd-tahoe-4-8l-help.131423/

 

[Rocket Man]

See the OP's other thread for the diag. https://www.tahoeyukonforum.com/threads/2005-2wd-tahoe-4-8l-help.131423/

Oh ok, I see he has extremely corroded connectors on the ECM harness. That’s going to cause all sorts of issues. Short circuits of all kinds there. @FLORIDA1 why do you have 2 threads going on?

 

[FLORIDA1]

Oh ok, I see he has extremely corroded connectors on the ECM harness. That’s going to cause all sorts of issues. Short circuits of all kinds there. @FLORIDA1 why do you have 2 threads going on?

Sorry, really my first time posting on the forum.
Really didn't know where to post to start with.

 

[Mudsport96]

Yeah, this is probably a cross issue with the other. The injector pins in the connector are probably getting voltage when they shouldn't and causing problems

 

[RET423]

The A/C fans kick on when the high pressure side of the A/C reaches its maximum designed pressure, if the pressure does not drop quickly enough the system is supposed to cut power to the A/C compressor to save it from locking up and destroying it.

It sounds like your high pressure safety switch is not disengaging the A/C clutch when it should, so your fan comes on but the compressor keeps pumping up the pressure until it starts locking up (and stalling the engine)

The pressure switch is likely bad but it also sounds like you have too much freon or significant moisture in the system if the high pressure lockup is occurring that quickly after the fan kicks on.

 

[Rocket Man]

The A/C fans kick on when the high pressure side of the A/C reaches its maximum designed pressure, if the pressure does not drop quickly enough the system is supposed to cut power to the A/C compressor to save it from locking up and destroying it.

It sounds like your high pressure safety switch is not disengaging the A/C clutch when it should, so your fan comes on but the compressor keeps pumping up the pressure until it starts locking up (and stalling the engine)

The pressure switch is likely bad but it also sounds like you have too much freon or significant moisture in the system if the high pressure lockup is occurring that quickly after the fan kicks on.

See post #2 of the OP’s other thread for the problem. It was extreme corrosion on the ECM harness connector, likely shorting the fan voltage to a couple injectors.

2005 2wd Tahoe 4.8L (HELP)

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