Technically Speaking
- Subject: Harsh or erratic upshifts/downshifts; DTC P2544 stored
- Unit: AWF21 (TF-81SC)
- Vehicle Applications: Ford Five Hundred, Mercury Montego
- Essential Reading: Rebuilder, Diagnostician
- Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor
This article is a complement to this month’s Shift Pointers article titled “Which Came First, the Chicken or the Egg?” If you have yet to read it, after you’re finished reading here you may want to flip over to page 60 and give it a read.
The Ford Five Hundred and Mercury Montego for a short time used a six-speed front-wheel-drive transmission (Figure 1) called the AWF21, also referred to as the TF-81SC (Figure 2).
Ford’s Technical Service Bulletin 05-1-6 refers to this transmission having harsh or erratic upshifts/downshifts accompanied by the wrench light illuminated and DTC P2544 stored in memory in vehicles built prior to 1/7/2005.
The bulletin does not provide a definition for code P2544 but does go on to explain that there may be PCM and TCM calibration issues that can be resolved with a reprogram procedure.
But then it says: If other DTCs are present in addition to the P2544, address the other DTCs first through normal diagnostics, then reprogram the PCM and TCM.
Although reprogramming vehicles built prior to 1/7/2005 with this new calibration is suggested, this statement also implies that other codes may be the reason for the setting of code P2544. Trying to correct this code prior to any other may put egg on your face.
So what is P2544? Code P2544 is a torque-management-request input signal A that may set when data received from the PCM or engine components are not correct for the vehicle conditions. Incorrect engine-torque calculations may result. The manufacturer describes symptoms of this code as follows: The transmission may enable limp-home strategies or increase pressure. Engine components may set additional DTCs. P2544, fuel-monitor error, ECT-sensor failure and MAF failures may be present.
Recently here in Miami, José Garcia of ATSG was called out by a friend of his who had a 2005 Ford Five Hundred (Figure 3) with the complaint of erratic and harsh upshifts and downshifts followed by intermittent failsafe. He told José that there were two codes stored, the P2544 and P0106: MAP/BARO Sensor Range Malfunction.
The technician was not sure whether these two codes would cause the transmission to go to limp. José was able to locate this TSB before going to see the vehicle but did not know what P2544 meant, nor did he have knowledge of the symptoms associated with P2544. What he did know was that P0106 needed to be addressed.
When he arrived, it took some time to find the MAP sensor, as it is buried between the firewall and engine (Figure 4).
When José located it he found a loose vacuum hose, as it was saturated in engine oil (Figure 5). Once a new end to the vacuum line was installed with a secure fit to the MAP sensor, the codes were erased and the transmission operated correctly. This may have indicated that the new calibration could have taken place previously.
Of course, the engine-oil leak is another problem that will need to be addressed, but this incident is an example of the far-reaching effects powertrain systems have. It’s not just engines, it’s not just transmissions and it’s not just ABS. It’s a complete package. For this reason we can see how one code sets another, and in this instance an engine-related sensor (MAP) produced a fault code affecting torque load. This in turn caused a torque-management-request code, as the torque reduction could not be performed. The effects were a transmission with erratic and harsh shifts, as both line-pressure and shift-scheduling strategies are affected by engine load. Eventually the problem was severe enough for long enough to place the transmission into failsafe to protect itself. The reason there were no related transmission codes is that there were no transmission malfunctions! The transmission was just fine.
A final point regarding engine-torque reduction is that it is a strategy being used on several fronts. The most-obvious purpose is fuel economy, but it is also used for various shift strategies eliminating tail-end bumps on a shift. And yet another use of engine-torque reduction is in traction-control systems helping the driver to maintain control of the vehicle during wheel-slip conditions.
As a result, several modules in a vehicle system can be communicating with the PCM to reduce engine torque under various conditions. If there is a reason one of these modules cannot perform that task, a code will set in that module, disabling the function while alerting a repair technician of its state. Most of these torque-request codes do not inform you that other codes stored elsewhere in the network could be the reason for the torque-request code being stored. So it becomes a question of which came first, the chicken or the egg? If there are other codes related to fuel, temperature, engine load or converter clutch, chances are they are the reason for your torque-request code.
