What does it mean?
SPECIAL NOTES: Non-professional mechanics should note that diagnosing code P0614 – “Engine control module (ECM)/transmission control module (TCM) –mismatch”, almost always requires the use of advanced, dealer-grade diagnostic equipment.
While this code is frequently caused by the failure of the PCM, it can also be caused by a failure of the TCM (Transmission Control Module, or by wiring faults in the CAN (Controller Area Network) bus system, which cannot be accessed by cheap, generic code readers.
It should also be noted that while it may sometimes be possible to repair code P0614 on a DIY basis if the cause is obvious, attempting to diagnose/repair this code if the cause is not obvious and the required equipment, skills, and reference data are not available could result in extensive, if not always fatal damage to the application’s electrical system.
For this reason, it is important to note that the information provided here is intended for general informational purposes only, and it should therefore NOT be used in any diagnostic/repair procedure for this code without making proper reference to the repair manual for the affected application.
Thus, if the few generic diagnostic steps outlined here do not resolve this code, the better option is to refer the vehicle to the dealer or other competent repair facility for professional diagnosis and repair. END OF SPECIAL NOTES.
OBD II fault code P0614 is a generic code that is defined as “Engine control module (ECM)/transmission control module (TCM) –mismatch”, or sometimes as “Engine control module (ECM)/transmission control module (TCM) – Incompatible”, and is set when a mismatch in communication (or a failure to communicate) between the PCM (Powertrain Control Module) and TCM (Transmission Control Module occurs.
Note that on some applications, the code will be set and a warning light illuminated on the first failure, while on others, up to 8 failures need to occur before a warning light will be illuminated. In the context of code P0614 and its definition, the word “mismatch” refers to a breakdown in the effective communication between the PCM and TCM.
This communication happens in the form of input data that is received from multiple sensors and other control modules that is distributed to all affected control modules via the CAN bus system. Typically, the PCM acts as the “clearing house” for all received input data, but for the PCM to be able to control all engine functions effectively, it requires accurate and valid data from multiple control modules.
We need not delve into the complexities of the CAN bus system here, but it should be noted that for the engine and transmission to work as intended, the communication between the PCM and TCM needs to be in perfect harmony without any “glitches”, interruptions, or mismatches between input data sets.
For instance, based on current operating conditions such as throttle position, road speed, selected shift mode, and the currently selected gear (among others), the PCM might determine that a gearshift is required. This command will be sent to the TCM, which will acknowledge the request, and initiate the gearshift.
However, should a malfunction or fault in either or both the PCM and TCM, or in the CAN bus system wiring exist that prevents effective communication between the various control modules that are affected by the gear shift request, the PCM will interpret the breakdown in communication as a mismatch between itself and the TCM, and set code P0614 as a result.
Depending on the application, a warning light might also be illuminated, but in some cases, the code will be present as “pending” until the required number of failure cycles have occurred. It should also be noted that since control modules other than the PCM and TCM are involved in the effective management of the transmission and hence, gear shifts, the breakdown in communication can occur in one or more other control modules. Typically, control modules such as the ABS Contro