Go directly to: PCM Reprogramming
A total of 14,370 AT (automatic transmission) Miatas from the 2016-2019 model years, along with 8,933 AT 124 Spiders from MY 2017-2019 [U.S. market, through mid-December 2018] are being recalled, because the transmissions could suddenly downshift into 1st gear without warning, resulting in “an unexpected and abrupt deceleration”, which both automakers fear could result in a crash. The problem has been traced to missing conditional programming for potential EMI (electromagnetic interference) conditions in the transmission control module (TCM) firmware, although I’m not sure if a CAN message was perhaps garbled and misinterpreted, or just EMI in general.
Fortunately, no related crashes or injuries are known and the automakers very much want to avoid this ever happening. Assuming that the beta testing of the firmware has been successful, and the distribution to the network of Fiat dealerships is in the works, we should soon receive a notification in the mail asking us to bring our cars into a dealership in late March / early April (at no cost to the vehicle owner), so that a technician can connect their Mopar diagnostic equipment into the OBDII port, to flash (overwrite) the existing firmware within our TCM (part # 05150944) to firmware level AF.
Part 573 Safety Recall Report 19E-008 [edited]
Manufacturer Information :
Manufacturer Name : Aisin World Corp. of America (AW)
Address : 15300 Centennial Drive
Northville, MI 48168
Number of potentially involved : 24,265
Estimated percentage with defect : 1 %
Description of the Defect : Vehicles with automatic transmissions using this TCM with a changed shift range detection system on vehicles manufactured since 2016MY may experience electrical noise in the range signal (such as “Neutral” and “Parking”), which may be detected by the TCM unit while driving in “D” range (including in “Manual” mode). In the Mazda vehicles, this electrical noise’s interaction with the control logic of the clutch control software may result in the vehicle downshifting unexpectedly and an abrupt deceleration of the drive wheels. This report is filed in accordance with 49 CFR 573.3(f) because AW supplies a similar TCM to FCA, but to date, AW is not aware of any reports of this condition manifesting itself in the FCA vehicles.
Description of the Safety Risk : Each affected OEM should evaluate the potential safety risk in its vehicles. An unexpected and abrupt deceleration could potentially increase the risk of an accident under certain conditions.
Description of the Cause : The control logic in the TCM’s internal software does not appropriately account for the electrical noise.
Identification of Any Warning that can Occur : None.
September 2016: AW received a Field Quality Information Report (FQIR) from Mazda reporting a downshifting issue.
November 2016: AW investigated the inhibitor switch and found no failure.
August 1, 2018: AW received a second FQIR from Mazda and commenced an investigation into the issue.
August – December 2018: AW investigated the inhibitor switch, automatic transmission, and Onboard Data Recorder (ODR) data. Analysis of the ODR indicated that a driveline shock occurred along with deceleration of the vehicle, when noise of the range signal was detected while driving in “D” range. Mazda requested to perform a re-creation test by simulator for the TCM. AW replicated the same phenomenon reflected in the ODR data by utilizing a TCM simulator. No failure was found in the inhibitor switch and automatic transmission. AW continued data analysis of the automatic transmission control program. AW reviewed the automatic transmission control program and the internal logic of the TCM and began developing changes to its internal logic.
December 15, 2018: AW began production of TCMs with software modification into the mass production line for Mazda.
January 31, 2019: Mazda informed AW that it had determined this issue presented a safety-related defect in its vehicles.
January 31, 2019: AW’s Regulatory Safety Committee reviewed the information from Mazda and determined that, because AW supplies this TCM to more than one OEM (Mazda and FCA), it would report the issue to NHTSA in accordance with 49 CFR 573.3(f).
AW is aware of two complaints from Mazda and zero complaints from FCA relating to the affected equipment. AW is not aware of any accidents or injuries related to this issue.
[UPDATE 4/3/2019, 5/3/2019]
I just learned that the dealers have now received the updates, and are now installing them to all applicable unsold vehicles on their lots, as well as sold vehicles (by appointment), as they are brought in. Be aware that concurrently, the dealers have apparently also been instructed to flash the PCM (power control module, aka ECU; part # 68231492) to firmware level AK, so that the “customer experience will be improved”…
- AD ~ some of us with MY 2017 Spiders may still be at this “original” firmware version, which already had the T19 recall fix incorporated, that sometimes limited engine speed (to idle) when fully depressing the gas pedal
- AE ~ is the U76 emissions recall, mandatory for California vehicles (may have been “ignored” in other states) to address software calibration that may inadvertently suspend some required OBD monitors, when the P1D7F fault code is set
- AF, AG, and AH ~ unknown change(s)*
- AI ~ consequently, most of the earlier Spiders probably never got this PCM update to alter the engine operating temperature vs. time algorithm, so that the CEL (and the P0128 trouble code) isn’t illuminated for marginal thermostat behavior, especially for North American market thermostats, which are spec’d differently
- AJ ~ unknown change(s)*
- AK ~ improved ambient temperature algorithm, so that the displayed “outside” temperature will more quickly reflect the actual temperature
NOTE: If you have installed a modified aftermarket PCM tune, because the firmware version will have been modified to include the changes listed, you may need to obtain a tune update, prior to attempting to re-flash that tune. Consider asking the dealer to skip this optional update, if you are in this situation (or at least returning your PCM back to stock configuration prior to your dealer visit).
* Other reported differences, that are presumed to have been intentional, include:
- briang reports (and other Miata drivers too) that the annoying difference between the metric Cruise setting (KM/H) and the actual speed, seems to have been corrected in one of these versions.
I have installed digital speedometer tweak, and [now the] Cruise [speed setting] value, digital [GPS] value and standard speedometer [value] all match when cruise is set to 100 km/h now, whereas prior to recall, I needed to set to 105 km/h to get 100 km/h.