Volvo fh12 ishift problem

The first thing I would recommend is that you take your Volvo over to either your dealer or a good independent transmission shop and have them run a complete diagnostic with an OBD-II scanner. The scan will show the general areas where there are problem and, if you are lucky, one of the scan codes that is stored in memory will show the exact problem.

You may wonder why the diagnostic results don’t provide you with the exact information you need, which is a good question. The answer is simply that the scanner isn’t designed to work with the transmission control module specifically. It is designed to work with the engine control module which is the master computer for the engine. Essentially, it is a master library that not only stores trouble codes that may be generated, but it also holds the software libraries that your engine needs to function correctly. The transmission’s control software is stored in and handled by the transmission control module. The module also generates error codes that are stored in the engine control module’s memory.

Because there are so many potential variables and possible problems involved it is nearly impossible to generate an exact error code to match a problem. The codes give you a range of problems that may be occurring. The point here is that the codes also will tell you generally where the problem is originating.

With that said, it is quite possible that your transmission is hanging somewhere so that computer messages aren’t getting through. In this condition, your tranny can easily go into limp-home. That’s why you need the diagnostic scan and error codes. There are so many possibilities that the scan will point you in the direction you need to go.

In your case, I would also suggest having the engine control module checked along with the transmission control module as they may be either failing or in the process of failing and generating the limp-home code. And, while you are at it, have the technician check all of the sensors that may be interacting with the control modules. In 2005, your Volvo was manufactured by Ford and so the tranny would likely have interacted with about a dozen or so sensors (the Mass Air Flow, the Manifold Air Pressure or the Throttle Positioner Sensor, for example) so it also makes sense to have them checked out.

Next, have the solenoid packs in the valve body checked. There may be as many as three solenoids in your transimission. They control the selection of the proper gearing for a given range of speed and engine rpm. If one or more of the solenoids has failed your transmission will automatically go into limp-home mode.

If nothing turns up in those checks, it’s time to start thinking about replacing the transmission as the piecemeal cost of repairs that might be needed will rapidly build up and past the cost of a rebuilt transmission.

Let me know what you find, I am interested in finding out.