| Torque management request, input signal A - malfunction ·
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|Wiring, ECM, TCM
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Table of Contents
- What Does Code P2544 Mean?
- What are the common causes of code P2544?
- What are the symptoms of code P2544?
- How do you troubleshoot code P2544?
- Codes Related to P2544
- Get Help with P2544
What Does Code P2544 Mean?
SPECIAL NOTES: Non-professional mechanics should note that code P2544 only indicates the fact that a torque management request has failed. It does not identify any particular system, component, or wiring harness in which a failure had prevented the torque management request from being received, confirmed and acted upon. In practice, this means that if the cause of the failure is not obvious, it might be necessary to interrogate the entire CAN bus system, which is something that requires professional grade diagnostic equipment, above average diagnostic skills, and very often, expert-level knowledge of the affected application.
For this reason, the information presented here is intended for general informational purposes only, and it should therefore NOT be used in any diagnostic procedure for code P2544 without making proper reference to the repair manual for the application. If the few generic diagnostic/repair steps outlined here do not resolve the issue, the better option is to refer the application to the dealer or other competent repair shop for professional diagnosis and repair.
Be aware that ill-considered or incorrect diagnostic methods can, and almost certainly will, cause extensive, if not fatal damage to the applications’ electrical system as well as to one or more control modules. END OF SPECIAL NOTES.
OBD II fault code P2544 is a generic code that is defined as “Torque management request, input signal A”, or sometimes as “Torque management request, input – malfunction A”. Regardless of the actual wording, the presence of code P2544 indicates that a torque management request has failed for a period of time set by the manufacturer.
Almost all manufacturers use a strategy known as “torque management” on automatic transmissions to reduce harshness during shifting, as well as to extend the life of the transmission’s internal components. This strategy is particularly useful on powerful, high-end applications in which hard acceleration can cause serious mechanical damage to a transmission.
In simple terms, the system uses input data from various engine sensors and control modules such as the fuel control module, ignition timing control module, transmission control module and others (depending on the application), to momentarily retard the base ignition timing just before and during a gear shift event. In a fully functional system this effectively reduces the engine torque, which has the effect of improving the “feel” of the shift pattern; in fact, on some applications, this system is so refined that gear shifts happen virtually seamlessly.
In terms of practicalities, the TCM (Transmission Control Module) sends a torque management request to the PCM (Power Control Module) via the CAN (Controller Area Network) bus system when driving conditions require it, such as during aggressive acceleration. When the PCM receives the request, it retards the base ignition timing sufficiently to make the gear shift happen smoothly. At the same time, the PCM communicates with the TCM to confirm that it had received the torque management request.
However, if any fault, defect, or malfunction in any part of the engine/fuel management system(s) is present at the time the request is made and the PCM cannot execute the request because of such a fault, defect, or malfunction, it will let the TCM know that the request had failed. Note that the number of failure cycles required before this code sets and a warning light is illuminated, varies between manufacturers. In some cases, code P2544 will set on the first failure, while on others as many as eight or more fault cycles need to occur before the code will be set and a warning light is illuminated.
NOTE: While failures of the CAN bus system can cause a torque management request to fail, CAN bus related failures will generally not set code P2544. Failures of the CAN bus system are almost invariably indicated by a series of dedicated codes, and one or more of these codes may therefore be present along with P2544. Note though that cheap, generic code readers can generally not access the CAN bus system, which means that a code readers’ inability to display CAN bus system related faults must NOT be taken as evidence that such faults are not present.
The image below shows a hugely simplified schematic of the circuits and control modules that are involved in generating and managing torque management requests. Not that due to the complexity of the circuitry involved, it is often more cost effective to refer the application for professional diagnosis and repair of code P2544.
What are the common causes of code P2544?
Some common causes of code P2544 could include the following-
- Unlike most other codes, the failure of a system driver circuit in the PCM or other control module is a relatively common cause of this code. However, unless the PCM had been reprogrammed for any reason in the recent past, look for the fault elsewhere before the PCM is replaced or reprogrammed.
- Some types of PCM reprogramming, such as installing performance settings, can damage or corrupt drivers and other circuits in the PCM and/or other controllers. If all other repair attempts have failed, reprogram the PCM to stock settings, and/or remove/disable/disconnect piggy-back performance chips (if such chips are present) before replacing the PCM
- Defective, or corrupted software in the TCM (Transmission Control Module)
- Damaged, burnt, shorted, disconnected, or corroded wiring and connectors
- Bad electrical connections almost anywhere in the engine/fuel management system(s)
- Bad or poor electrical connection(s) almost anywhere in the CAN (Controller Area Network) bus system
What are the symptoms of code P2544?
Some common symptoms of code P2544 could include the following, but take note that the severity of especially driveability related symptoms can vary dramatically between applications-
- Stored trouble code and an illuminated warning light. Note that in cases where no warning light is illuminated, the code may be stored as “pending”.
- Some applications will display harsh, or even erratic shifting
- Fuel consumption may increase
- Engine may stall during idling, or at low engine speeds
- Idling quality may deteriorate, or the engine may not idle at all
- Overall performance may decrease over the engines’ full operating range
NOTE: Severe mechanical damage to the transmission could result if code P2544 is not repaired in a timely manner.
How do you troubleshoot code P2544?
SPECIAL NOTES: While it is sometimes possible to resolve code P2544 on a DIY basis, non-professional mechanics should take note that it is generally not possible to access the CAN bus system with cheap, generic code readers. For this reason, is NOT recommended that the diagnostic procedure for this code be taken beyond the few generic steps outlined here. Also bear in mind that disconnecting the battery in an attempt to “clear” the code is NOT recommended, as this could result in other codes being set, as well as cause the PCM and other control modules to lose vital programming and functionalities, which requires extensive reprogramming to remedy. END OF SPECIAL NOTES.
Record all fault codes present, including “pending” codes, as well as all available freeze frame data. This information could be of use should an intermittent fault be diagnosed later on.
Since one of the most common causes of this code is bad or degraded ground connections, consult the manual for the application to locate all electrical ground points.
Locate, inspect, and repair all ground connections, including the main grounds between the battery, engine, and chassis. However, before disconnecting the battery ground, make sure to install an approved memory saving device as per the instructions provided in the manual to keep critical systems in the PCM and other control modules powered up when battery power is removed.
TIP: One good way to check for ground issues is to connect a jumper cable between the battery negative terminal and a suitable grounding point on the engine. If connected properly, this additional ground replaces the original ground cable/strap so if the fault does not show when the vehicle is operated with the additional ground in place, inspect and repair the original battery ground connections. If this test does not produce positive results, repeat it between the negative battery terminal and all other ground points by using wire of the appropriate gauge, but make sure that all connections are made with suitable clips or clamps to ensure proper connectivity.
NOTE: A poor or degraded battery ground can cause a wide variety of electrical issues and codes to be set. Bear in mind therefore that unless random issues with especially the security/anti theft system, central locking, or other body components are present, do not disconnect the battery ground before all other ground connections have been inspected and repaired. In fact, do not disconnect any battery terminal(s) unless it is absolutely necessary to prevent the possible loss of programming and/or functionality of the PCM or other controllers.
Clear all codes after repairs are complete, and operate the vehicle normally for about 15 miles or so to see if the code returns.
If the code persists, and there are other codes present along with P2544 that relate to engine/fuel management issues, consult the manual to identify the reference voltage circuit(s) that emanate from the PCM. On many applications, several sensors and circuits share one, or both reference voltage circuits, which means that any fault, defect, or malfunction in either a sensor or a sensors’ control circuit directly affects the operation of all other sensors and circuits that share that particular reference voltage circuit.
Set the scanner to monitor each reference voltage circuit, and disconnect all sensors that share that circuit, but do not disconnect them all at once. Disconnect each in turn; if a sensor or circuit is defective, the scanner readout will usually (but not always) change from showing a fault, to “OK” when the defective sensor or circuit is disconnected.
If the scanner display does not change to “OK” after having disconnected all the sensors and circuits on one reference voltage circuit, repeat this test on the other reference voltage circuit. If a fault is identified in this way, perform resistance, ground, and continuity tests on all relevant wiring and components. Make repairs as required, clear all codes after repairs are complete, and operate the vehicle normally for about 15 miles or so to see if the code returns.
NOTE: Be sure to disconnect the circuit/system being tested from the PCM and other control modules to prevent damage to the controller(s).
If all ground connections, reference voltage circuits, and all sensors check out perform a thorough visual inspection of all wiring between all relevant control modules. Look for obvious signs of damage to wiring, disconnected wiring, shorted wiring, or wiring and/or connectors that are corroded. Make repairs, or replace wiring as required.
NOTE: Be aware that this inspection usually requires that all wiring harnesses associated with the engine and fuel management systems be opened to check for damage or issues that may be hidden by the harnesses’ insulation. This is a major undertaking on any application, and it may require the removal of carpets, the dashboard (or parts of the dashboard), trim panels, and consoles to gain access to all wiring. Moreover, there is no guarantee that visible damage will be found, but bear in mind that absence of visible evidence should not be taken as evidence of the absence of faults.
The steps outlined above may or may not resolve code P2455. If they do not, remember that continuing the procedure beyond Step 4 requires the use of sophisticated professional grade diagnostic equipment, expert-level diagnostic skills, color-coded wiring diagrams, unambiguous pin out charts, and reference data in the form of pressure-to-Hertz (or OHM) charts, temperature-to Hertz (or OHM) charts, and possibly an oscilloscope and waveform libraries with which to interpret waveforms obtained with the oscilloscope.
Since few, if any non-professional mechanics possess the above-mentioned skills, equipment, and reference data, the better option at this point would be to refer the application for professional diagnosis and repair.
Codes Related to P2544
- P2545 – Relates to “Torque Management Request Input Signal “A” Range/Performance”
- P2546 – Relates to “Torque Management Request Input Signal “A” Low”
- P2547 – Relates to “Torque Management Request Input Signal “A” High”
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