Wierd MAP reading
 

In diagnosing a driveability concern with my LS swap, I was looking at the data stream on my scanner. The MAP is showing between 11.2" and 12" at 675 rpm. Thought that was a little low for the cam I'm using, so I put my shop vacuum gauge on the nipple on the plenum. It was registering a steady 19" at the same time. Thinking I had a bad sensor, I replaced it. Guess what! The new sensor reads the same. I know the rear of the plenum is a vacuum source for the power brake booster, so I blocked the vacuum line. No change. Any ideas? As a side note, the truck goes instantly into limp mode when trying to drive. All of my peripherals seem to be okay, diadnostically. Would a bad PCM send a bad ref. to the scan reader, or should I be looking elsewhere?. I've got no vacuum leaks that I can find. Thanks

Re: Wierd MAP reading
 

Is the MAP sensor calibrated correctly within the tune?

Re: Wierd MAP reading
 

Can't answer that question. Until I can get some help from someone with HPTune that can read my system, I'm shooting in the dark, here. The initial reflash was to get the truck up and running with a base tune, but the truck can't even do that. It will idle all day long but will go into limp mode as soon as I try to drive it. I have switched voltage to the trans. and I can ground each shift solenoid manually (PCM connectors removed) and hear them operate, point to point wiring is good, with no shorts/opens/grounds on all of the operating devices. And, no DTC's...

I may have someone knowledgeable coming over soon to help, that has Tuner knowledge. Keeping my fingers crossed that this actually happens

Re: Wierd MAP reading
 

I am confident that Mike can fix it using hp tuners, patience

Re: Wierd MAP reading
 

AK, you have NO idea how appreciative I am to have Mike come over. I'm running out of hair to pull out....

Re: Wierd MAP reading
 

It is a very long 5 minute drive for him to travel to see you............

Re: Wierd MAP reading
 

Your MAP sensor readings are very close to your Gauge readings....

Converting your Gauge reading to Absolute pressure reading that the Data Stream is reporting...

29.92-12=17.92