Tundra Flex Fuel 5.7 Engine Cranks then loses power

Hello everyone,

So a few months ago I started getting an issue where A/T fluid warning light, engine light, and battery light comes on and truck wont start at all.
I took it to a mechanic shop and they said that the issue was with the fuel pump driver module and costed $830 to replace it with OEM. After they replaced it, truck started fine.

No more issues until a month later. Same error lights on the dash, no crank no start. I took to Toyota and they said that the issue was the starter and it needed to be replaced, so I paid to have that fixed

Then I had no more issues until a few weeks ago I drove to Lowes and came back and started the truck and heard a concerning rattling sound from the engine, and also experienced loss of power. I turned it off, and tried again a few times and then those same error lights came on the dash and the engine was steadily losing power.

I got it towed to a different small town mechanic shop, and they said that there is an issue in the fuel lines somewhere because no fuel is reaching the engine. I explained to him the history of this issue, and he says that there is either a faulty fuel pump driver module installed or some kind of electrical problem. I asked him to check the fuel injectors, and he says theres no issue there. After diagnosing, he says the issue is a bad fuel pump and wanted to replace it.

Right now the truck is at Toyota again, but the truck is again starting fine so they can't figure out the issue. They're saying theres no codes coming up.

I have been dedicating hours researching what this could be. I don't think a bad fuel pump would be an intermittent issue because the issue only happens when I am trying to start the truck. Once I have it running, the engine runs perfectly fine.

My question is what could this be. I've seen a forum regarding the 5.7 Flex Fuel tundras and that they need to have the ECM re-programmed with a new updated fuel pump, also some other ideas are possibly a secondary air injector issue, or bad coil pack.

I know it's difficult because there are no codes coming up, but I have to get this figured out otherwise I will have to sell the truck because no one can figure it out and I can't have a vehicle that is always breaking down.

 

Update: I went back on the Tech notes I received from Toyota, they did manage to find a code. The code is P0230 - which is a generic code for the Fuel Pump Primary Circuit Malfunction. Did quite a bit of research and this indicates there is low voltage in the main power circuit of the fuel pump relay. So it's an electrical issue. Some ideas of what it could be is an issue with the ECM, FP relay, the driver module or an electrical short in the pump. Going to have to bring it to the shop again to have it diagnosed further

 

I also purchased a OBD II connector so I can download techstream and connect to the ECM. I am considering re-flashing the ECM and erasing the alcohol density to see if that fixes the issue also - right now the alcohol density is at 9%

 

Hopefully someone will be along soon to help you diagnose the problem. Electrical problems can be maddening.

 

Just a mini update. Yesterday while I was driving home, about 5 minutes into the drive I stop at a light. When going to accelerate, I barley push down the pedal and the engine sputters and RPM shoots up and it sounds almost like its drowning. Driving down the road, I try to push the gas pedal even more and then the engine would lose power and would not speed up as normal. Shortly after, the "4LO" orange light starts flashing, and I pull over. After 5 minutes of idling in park, the flashing "4lo" goes away and then it drives normally. (By the way I haven't touched 4WD in about a year, so I doubt it has anything to do with the drivetrain.) Unsure if this has anything to do with the limp mode issues as I have noted in this thread, but it seems like its correlated. This specific issue is pointing more to a secondary air injection issue. I have not tried to run it for any codes yet.