03 GMC Yukon Denali 6.0
 

At my wits end. Vehicle been in shop for 6 weeks, guy still has no clear idea whats wrong. Vehicle is in Reduced Power mode and Service Stability messages are showing. Vehicle will crank and then die with in just a couple of seconds. Throttle body, Fuel pump new ground cables, and a few harnesses not sure which ones have all been replaced to no avail. Guy is now thinking PCM. Is this possible and upon looking for a PCM no major parts stores show this option only ECM. Are these 1 unit. Any help would be greatly appreciated.

It would be helpful if we had any codes that were stored in it. Otherwise, we can play guessing games all day.

Not able to pull codes. saying that he cant communicate with PCM with scan tool

Last time light came on I got cylinder three misfire, that was several months ago. Vehicle ran fine one day, went to crank next day and it went straight into reduced power.

You are not able to communicate with any module? If the network is down you need to start unplugging modules until the network is up. Start with those that flagged last. Stabiltrac

PCM=ECM

Now that that's settled, we need to know more information. Remember, we're on the other side of the keyboard and only have the picture that you paint for us.

1. How many miles on this car?

2. How long have you owned it?

3. How many miles have you owned it?

4. Do you know its history?

5. What region does it live in?

6. Does this region salt their roads when they treat ice/snow?

7. Any recent trauma (crash/flood/fire/fruit juice spilled down the dash/etc.)?

8. Any recent repairs prior to the problem starting?

9. Is this mechanic a dealership or chain or private?

10. Is this mechanic being paid by the hour for all of this six weeks' worth of troubleshooting or are they being decent about it?

11. I know you said it starts and dies. You also said it goes into reduced power. You also said cylinder misfire in #3. From this combination I suspect it runs sometimes. Does it?

12. When the engine off and the ignition in the [Run] position, does it show a check engine light at least temporarily?

13. If it does run, does it show a check engine light while running?

14. What is the fuel pressure with engine cold, engine off, ignition on?

15. What is the fuel pressure with engine cold, engine on and idling?

16. How old is the battery?

17. Has someone checked the to make sure the terminals are tight?

18. Has it ever had catalytic converters replaced?

19. Has someone tried removing the forward Oxygen sensors to see if it will start and idle?

20. How many miles have the current spark plugs been installed?

That's all I can think of for now.