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MaxxForce 7 Running Check Engine Code

This problem was pretty straight forward using the Navistar Engine Software that led us directly to the problem. The engine code was the fuel rail pressure sensor. Most times it’s the sensor but due diligence is in order here just in case there’s a bad wire end or poor connection down the line. This engine (MAXXfORCE 7) is in a 2008 school bus running up and down a long hill every day and keeping up with the daily 2 trips a day.

The routine is good for a diesel engine running at the proper engine temperature keeping those nasty hydrocarbons down to a reasonable level. There is a story behind this particular bus. It’s the one and only 2008 International bus we have in the fleet. The reason for that is it used to be a hybrid that had batteries that unfortunately failed disabling the hybrid system. They fried up one day and there was no follow up from the dealer on replacement batteries. They were removed and that was the end of the hybrid portion of this unit.

We turned this bus in to a regular diesel powered school bus without an engine brake. The hybrid used to be the drive line brake when it was working but no more. This bus got placed on an easy highway run. Fast forward to today and the fuel rail pressure sensor. It was located under the passenger side valve cover which took some work to get to. Once the sensor was located we tested the resistance and the wiring harness. Eventually we decided to replace the sensor and that turned out to be the problem.

This diesel would not start or run mainly because of a bad signal from the FRP. The engine computer reads all of the sensors and acts on the information received. If the fuel rail pressure sensor was sending a low pressure reading I can see the problem with poor performance. This is one occasion where the NED Navistar Engine Software indicated a bad sensor and that was the exact problem. Sometimes an engine code reading will lead you down the garden path causing some frustration.

The only other MaxxForce 7 diesel engines we have in the fleet are 2013 models so the design and specs are not similar due to different emission standards between 2008 and 2013. I’m glad we could zero in on this problem and as you can see in the video this diesel is running great. Another job to check off the “to do list”.