The exhaust back pressure (EBP) sensor going bad is a common problem in the 6.4 especially around 90-100K miles. It can be the sensor or a clogged tube going to the sensor. When this sensor starts malfunctioning, there is a tremendous loss of fuel economy. My truck went from about 18 miles per gallon to about 9.
I have a DashDaq in my truck and don’t use the tuning; I only use it for diagnostics. I have noticed early in the morning when I am warming the truck, I get a P006 code which is the MAP (manifold absolute pressure) sensor and EBP correlation is not matching up. My DashDaq was telling me I had plenty of fuel oil pressure, I could see my boost going up but I wasn’t feeling any thrust when I pressed the pedal, and I was seeing smoke coming out of the tailpipe. When you have smoke coming out of your tailpipe, you have too much fuel and not enough oxygen which means you don’t have enough boost.
The EBP sensor is absolutely crucial to the operation of the 6.4 because it helps the computer to determine how much turbo to add or take away in terms of making power. If the sensor is reading incorrectly, then you are not going to have as much boost. Boost is where the power comes from in these diesels. The sensor is measuring the pressure in between the combustion chamber and the turbo itself. If that reading is incorrect, then nothing else works right. The truck will feel like the fuel pump is going bad because it will have a little bit of power and then will pick up. Often a dealer will throw and bunch of parts at a truck that it doesn’t need and won’t catch this problem.
When I ran the computer diagnostic with the IDS (Integrated Diagnostic System), it revealed that both the MAP sensor and the EBP sensor were working correctly. MAP sensors very seldom go bad. The hose going to the MAP sensor might go bad, but the MAP sensor itself very seldom goes bad. A little piece of carbon buildup down at the exhaust pipe can cause this whole thing to go haywire. Get the EBP sensor and hose out of the way, and use a paper clip and work the hole and get any carbon out of there. Make sure it is clean. Mine had some carbon buildup on the tube but I went ahead and replaced the sensor because I’m going to be on the road a lot and I don’t need this thing screwing up on me. It has already warned me twice that it might be the issue. I am spending a little money proactively.
If you own a 6.4, it is absolutely crucial that you have a monitoring devise like the Spartan, DashDaq or Edge. Even if you don’t use the tuning, it is absolutely crucial 1) to keep an eye on your EGTs, 2) keep an eye on your engine cooling temp, your engine oil temps. If your fuel oil pressure is good and you see that your boost says you’re making it but you’re not (the truck is not going forward as quickly as it should), then you know you have a problem.
6.4s can be temperamental. They can be very difficult to diagnose because they are very complicated vehicles. With a little bit of diligence and data information from a DashDaq, you can find problems in your truck and take care of them before you go to the dealer and get jerked around. ~Bill Hewitt