Need help diagnosing Fuel System codes

[Andy H]

Hello everyone! I recently had a check engine light come on after filling up my truck with gas. It is a 2008 Silverado with a 5.3l LY5 J code with 190,000 miles. The codes I am getting are P069e and P0606, (which have to do with the Fuel Pump Control Module). My truck is running perfectly fine though, no problems at all. I started using my Blue Driver obd2 scanner to log data to help troubleshoot, because the codes would instantly come back as soon as I clear them. I was monitoring my fuel pressure and noticed it was running around 88 to 92 psi range according to my Blue Driver.

 

I kept driving the truck since it was running great and would occasionally monitor the fuel pressure for any changes. I noticed that once my fuel tank got down towards 1/2 a tank, The fuel pressure dropped to around 42 psi. At this point, I was able to clear the codes and the check engine light would stay off. As I continued to drive the truck, the fuel pressure stayed around 42 and the check engine light stayed off. When the fuel level got down to around 1/8 of a tank, I stopped and filled up the fuel tank. As soon as I started the truck up while at the gas station, the check engine light came back on, and the fuel pressure went back up to around 92 psi. Truck still runs good though. Any ideas what would be causing this to happen?

 

Thanks!

Andy

[redvett]

3 hours ago, Andy H said:

 

The P0606 code is a diagnostic trouble code that indicates a problem with the Powertrain Control Module (PCM) in a vehicle. The PCM is the computer that controls and assesses the vehicle's systems and components. The P0606 code is logged when the PCM detects an error, such as when the PCM software is outdated or the PCM is faulty. 

 

 

 

[Andy H]

So, do I need to replace the PCM?

[CamGTP]

No, not really. That code can come up with weird electrical issues or if something gets pissy over the CAN network.

 

Th P069e code is likely also causing the P0606 code. It's hard to say if the FPCM is to blame for the code or if another sensor is tripping the FPCM to send that code to the PCM.

 

These trucks should only run at 3-4 bar pressure or roughly 42-60psi. If it's running at nearly 90psi, something is telling the pump for max output. You don't want it to run at max flow all the time, it's bad for the pump and will also get the fuel pretty hot because it's being cycled through the pump so quickly.

 

Someone with a high dollar scan tool needs to get hooked up to this thing and start watching data logs to see if everything is within spec. I wouldn't want to shotgun a fuel pump or new FPCM at it just yet.