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Getting the Facts Straight - Repost
Posted to Technical Theory Forum on 12/12/2012 107 Replies


I have this truck that sets a code p0101 MAF sensor performance. The customer was at another shop for this same code and they replaced the maf but the MIL came on again shortly after.

This truck has an aftermarket ducting for the MAF.

I am using the ESCAN and trying to come up with some solid facts about VE and fuel trims.

Here are the screen shots.

This is long term fuel trims [ECM/Inputs/Outputs Scan Data]

This is short term. [0 , ECM/Inputs/Outputs Scan Data]

This is VE [2003 Chevrolet Silverado 1500 HD LS, ECM/Inputs/Outputs Scan Data]

During the ve test ,there is a definite problem between actual and calculated. Especially at the top where the actual does not reach the calculated.

The Long term fuel trims and short terms are definetely bad. BTW this engine has low power from a dead stop to WOT while doing the VE test.

I am trying to get some facts straight about the proper direction to look . (getting lazy with age). From the escan help menu there are some examples .One example was a truck with a maf system from a toyota.. From what i understood , if the ve is bad and if the fuel trims are within 10 percent + or - , then the problem is restricted exhaust or engine mechanical. In my situation , The VE is bad and the fuel trims are bad as well so then I can rule out exhaust restriction.(correct?) I can then think maybe the problem could be false air ,bad aftermarket MAF or the ad-on tubing for the MAF .Note I have smoke tested the intake gaskets for leaks and did not find a problem.

I would love to hear about facts to rule out componets to get to point to the problem for these systems.

Much apreciated..

Take care.

Mark from Ontario

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car Vehicle Data

2003 Chevrolet Silverado 1500 HD LT 6.0L

Engine6.0 L
Trans4-speed Automatic (Electronic)