2008 Sierra 5.3 Check Engine Light

[mustangcobra93]

I have a '08 Sierra with the 5.3.  The motor has 231,000 miles on it.  The check engine light has been on for awhile with no drivability issues.  Yesterday it started blinking and the truck starting running rough.  After a few minutes it stopped blinking and the truck ran ok again.  It stumbles at idle now.  I pulled the codes and here is what came up:  P0606, P0300, P0521 & P069E.  Any idea what might cause this concoction of codes? 

 

[richard wysong]

Please  ALWAYS post the code definitions, There are over 18000 possible codes and no one knows them all. PO300 is random misfire and caused the light to blink before setting a hard code. Start with the basics for that 1, check the plugs, wires and coils first then the injectors if all that is a-ok. A scan tool that does live data may show you which cylinder has the misfire

[swathdiver]

On 2/11/2023 at 4:14 PM, mustangcobra93 said:

 I pulled the codes and here is what came up:  P0606, P0300, P0521 & P069E.  Any idea what might cause this concoction of codes? 

 

 

The first and last are related to your fuel pump.  The P0606 says that your fuel pump control module has failed.  A replacement has to be programmed to your truck.  It's above your spare tire.

 

The P0521 is related to your oil pressure sensor.  As long as the wiring is good, the usual culprit for this code is that your ECM has gone bad but it could be the sensor.  

 

I would replace the sensor first if you don't have the proper diagnostic tools and for me, I like to remove the intake and change the sensor.  It takes a little longer but I don't have to do the job blindly and kill my back being a contortionist to get back there.