P0148 – High Pressure Common Rail Checksum Error (Dodge/Ram)
If there is no fuel smell, or if your test of the fuel lines and rails indicates no leaks, then the P0148 code is likely indicating a fuel control actuator (FCA) problem, or a problem in the fuel pressure sensor itself.
The FCA is an electronically-controlled valve that the engine control module (ECM) uses to control the amount of fuel entering the high-pressure pumping chambers. When the FCA is opened, the maximum amount of fuel is being supplied to the fuel injection pump. A fuel pressure sensor is located near the FCA to measure the amount of fuel being supplied to it. Either component can be at fault.
The FCA can be removed and tested by a competent mechanic with the correct tools for the testing. On many Dodge models, however, replacement costs are low and those with knowledge of high pressure fuel systems should be able to replace both the FCA and its pressure sensor easily.
Still, it’s worth nothing that you must be very careful when working on a high pressure fuel system. High pressure lines and rails can very dangerous if you are not trained to work with them, so do-it-yourself repairs should only be done by those who understand the system thoroughly. What’s more, it may be illegal to work on your own vehicle’s high pressure fuel system in some jurisdictions, at least if you do not have the proper certifications. Consider yourself warned.