Engine light codes along with mystery --more opinions needed.

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Baylee Brown

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P0102- Mass or Volume Airflow "A" Circuit Low Input
P0340- Camshaft Position Sensor "A" Circuit (Bank 1 or Single Sensor
P0440- Evaporative Emission System

* mass air flow sensor has been replaced
* camshaft position sensor has been replaced
* 2 new catalytic converters

I have reset the codes after installing this and the light still comes back on. more recently, the service 4X4 lights on and off but I believe its just the switch in the dash because 4wd works fine.

This just started too, when accelerating from a stop there are 3 to 4 jolts almost like the transmission is slipping or the engine is skipping. when coming to a stop it does the same thing. the power steering comes and goes mainly while stopped or turning into a parking spot is when I have this problem. I have a friend that works on transmissions and is going to call me back to see if the power steering has anything to do with the solenoids. these started two days ago and it's been raining on and off.

my gauges on the dash are fine, not overheating, voltage is fine, oil pressure is fine.
 

Big Mama

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For the p0440 it may be much simpler. Check your gas cap charcoal canister and purge valve I just fixed an evap code it was gas cap. The ps seems unrelated but hints at the pump when at low rpm. The jerking sounds tranny related as the check 4wd code could be.
 
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Baylee Brown

Baylee Brown

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For the p0440 it may be much simpler. Check your gas cap charcoal canister and purge valve I just fixed an evap code it was gas cap. The ps seems unrelated but hints at the pump when at low rpm. The jerking sounds tranny related as the check 4wd code could be.

Replaced the purge valve last year.
 
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Baylee Brown

Baylee Brown

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Update the Tahoe somehow switched to 4x4 by itself and that is what caused the power steering to seem like it was not working.
 

Sean James

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My local autozone had the 2hi, 4hi, auto, and 4low switch for $30. Snapped out the old one, snapped in the new one in 5 minutes. My '99 tahoe was randomly going from 4hi to 2hi to auto, freaked me out. Thank God it didn't go into 4low on the highway. Took a chance and that stupid switch fixed everything. Guess I got lucky.
 

Big Mama

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Yes, yes you did but good job checking the easy stuff first.
 
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Baylee Brown

Baylee Brown

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Here are the diagnostics for the P0102. The MAF is on the same circuit as the Evap, the issues may be related.

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Checked new maf with computer and the pcm wasn’t getting any information from it. Maf was at 0 g/s all the time. Replaced the fuse and now the pcm has information from the maf now. 100% better, no more hesitation when accelerating or under a load. While I had the computer, I was looking at the misfires it was having while idling and the computer barely picked up on it but the misfire had a distinct feeling. I’ll be replacing the injectors, already tried a whole bottle of chevron complete fuel system cleaner 32oz at a quarter of a tank. Still have the feeling after the cleaner. I’ll update after the spyder injector replacement.
 

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