After searching around for an answer to your MKX’s problem, I found it. The problem lies in the powertrain control module or PCM. The powertrain control module is the computer that controls the powertrain or the interaction between the engine and transmission, collectively known as the powertrain. Believe it or not, there are also individual control modules that take care of the transmission, or the transmission control module and the engine, the engine control module. In other words, one system in your car is controlled by three computer systems. In fact, in today’s cars there may be as many as 18 individual computer systems taking care of things under the hood. Is it any wonder that diagnosing problems has become a game of electronics?
With that said, in all my researching, I kept on finding references to the PCM and keeping its software updated. Granted, the PCM does control the entire powertrain so that while it may look like it is playing a minor role in the transmission’s action, it isn’t. Instead, it is handling more than you would think.
Indeed, it may be trying to take over from the TCM when the engine management module or EMM — the master computer — determines that there is a transmission problem but it cannot “understand” it. The EMM seems to poll the PCM first and then stores the result of the error before acting on it. When it does act on the information, it is quite likely that the transmission will buck and skip and act as you describe.
Here are my suggestions for handling this problem:
- Write down exactly what your MKX is doing and when it is doing it (mileage)
- Contact your dealer’s service department
- Bring your car into the service department
- Give the information you recorded to the service writer
- Make sure that a complete diagnostic is run with the latest software and proper OBD-II scanner
That’s a good starting point. Here’s what I think will be found. The PCM module needs an urgent update. Make sure that the technician obtains the latest upgrade software for the PCM from the Ford library. This should solve the problem.
If not, the problem may be in the valve body as one of the check valve may be lazy. The valve body sits on the outside of the transaxle. It is the device that initially sets up the gear choice you have made by directing the flow of transmission fluid to the proper clutches/bands and then gearing. The valve body contains a series of runners (channels) through which the transmission fluid is directed. Each runner in the valve body contains two check valves, one that energizes when the gear is chosen and the second which is energized when it is time for the fluid to flow.
The actual check valve is just a spring with a lightweight ball bearing held in place by a light spring. Each valve has its own control hardware that forces the check valve to open at the right time and then close, also at the proper time.
The most vulnerable part of the check valve is the spring. Though the springs are engineered to last there are times when the spring becomes compressed and its action is lazy. Indeed, there are times, in this situation, where the check valve may remain closed, suddenly spring open and work and then close again. This describes your MKX’s problem. It is an intermittent problem that is hard to diagnose on quick test drives that a service manager may make. It takes several days of constant driving, I’ll bet, before the problem appears and disappears and reappears again. Your best move here is simple, remove the valve body and replace all of the springs and ball bearings. This may seem like a big chore, but it is one of the easiest ones in the transmission because the device is on the outside of the transmission case.
The issue here is time. It is rather labor-intensive as there are several spring/ballbearing clusters that have to be replaced and that does take time and expertise. You are looking at about a $600 bill for this move.
If you have the check valve and software issues taken care of, the next move — and only move — is to get a rebuilt transmission and replace your current device. This will cost in the vicinity of $4,000.
