IORCET

The other day my mostly stock 99 Silverado set off code P0174. There were no noticable changes in the way it drove and it is not idling rough. I cleared the codes to see if it would come back and the SES light came back on today. This time I got P0171 and P0174. I hooked up my fuel pressure guage and key on engine off it read 53 psi. I know that is a couple psi low from where it should be. With the engine running the fuel pressure dropped to 50 psi. After shutting the engine off it maintained pressure at about 45 for well beyond 5 minutes. I had originally read that a dirty MAF could cause this issue, but with the fuel pressure reading being lower than it should be I was thinking fuel filter or pressure regulator. Any thoughts? Thanks for any help.

adam86107

Here's a thread about the same codes from a Camaro forum. Hope it helps.


http://camaroforums.com/forum/showthread.php?t=46599

jk11blueboi

I had the same codes p0171 and p0174. After replacing both my 02 sensors (first i had po1133 and p01153 and p0101) cleaned the maf and got new o2 sensors and p0171 and p0174 were the only codes that would be pending and stick around. i went to autozone and baught the fuel filter for 10 dollars and it fixed the problem.

but it could also be a vacuum leak at your intake gasket. get carb cleaner while the engine is running and spray near the intake. if the idle changes, then u have a vacuum leak. goodluck

ChankSon

I am having these same issues with my 99... I cleaned the MAF... No change... starting to notice that sometimes when i prss the gas it doesnt want to go... like hestitation. Then it gradually will get going.... I can here the fuel pump running at idle... Not out of the normal on these though... Gonna try and replace the fuel filter to see what happens there....

99ChevyZ71

Do you have the 5.3L engine? Are there really only two O2 sensors on the engine? I've gotten codes, though I forget the exact numbers, but one says front bank and the other says rear bank. I'm not certain what the front and rear bank are.

s34n

bank 1 sensor 1 and bank 2 sensor 1 is before the cat. bank 1 sensor 2 and bank 2 sensor 2 is post cat.

99ChevyZ71

So in otherwords, they don't tell which exact sensor, you just have to buy all of them. Are all the sensors the same?