Q: My titan recently began to shutter while I was accelerating. When it stopped I couldn't get it to go faster than 40mph.

My first thought is, what code is the TCM (transmission control module) setting? Usually when a vehicle won’t go faster than 40 mph, the vehicle has set itself into limp mode. It does this to protect itself from what it perceives to be greater damage. To begin to figure this out, a scan tool will need to be connected to retrieve codes and to observe the relevant data. Keep in mind, a code reader that is used at your local part store will not be sufficient. If you have access to such a tool and want to learn, connect it to the OBD-II connector and give it a shot.

In my research for the Titan, there is quite a bit of information about TCM reprogramming. Either the TCM’s are failing or they are needing what is called a reflash to fix your problem. Either way the TCM will need to be reprogrammed and this will require Nissan software to make this happen.

If you want to have this looked at by a professional, a certified technician from YourMechanic can come to your car’s location to diagnose your vehicle’s loss of power, scan for any codes, and determine what repairs will be necessary.