so ive been having some issues with my transmission, power and and MPG, and a good friend of mine who is a diesel mechanic says it may be a MAP sensor issue. is there a way to test it? the problem im having with the transmission is that it seems to be shifting too high, and when cruising at 65mph or higher and you let off the gas, it seems to down shift, almost feeling like an engine brake. im also experiencing a lack of power, which could be attributed to the transmission or the fact that i have 178k miles and an O2 sensor code which im still tracing. he also mentioned using a thicker oil to remedy my lifter knock. any inout on these is GREATLY appreciated.

 

I didn't think our trucks had a MAP sensor? From what I have been learning in school our trucks are ran off the MAF sensor. I could be wrong but I would check that to see if its dirty or the wires there are broken.
Someone correct me if im wrong cause I might be.

 

I wasn't quite sure either, but there is one on eBay listed for this engine and year. This transmission only has about 44k miles on it and im really hoping that it's not already going out. The only thing I can think other than the sensor would be that a servo got shorted out when a bare spot on the wiring harness grounded out and popped the fuse under the hood. In February

 

You have a MAF, not a MAP. Don't buy sensors on Ebay.

What are the exact code numbers?

Is this a stock truck or do you have mods? If you have an oiled type air filter, it can foul the MAF.

 

I do, the trick had an airraid when I bought it. And I posted the codes in a thread a few days ago, P0156
P0161. And the truck has a Diablo tuner, cat-back, CAI, 4R75E transmission, and the rest of the mods are non-mechanical.

 

Clean your MAF.

 

Your two fault codes will not be caused by a MAF sensor, but they will be caused by a defective or disconnected downstream driver's side O2 sensor. This sensor, however, won't affect drivability.

 

so there still may be a fault in the downstream sensors wiring. will that effect the front sensors ability?

 

No. The downstream sensors are used only to monitor the converters.