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Cherokee flash details

by David Zatz on

Chrysler has issued a service bulletin that clarifies the “flash” upgrade, which updates the transmission control software on Jeep Cherokees built before May 5, 2014.

Bulletin number 21-018-14 points out that the software helps overall shift quality and throttle response, with specific improvements to:

  • Shifting out of park
  • Automatic downshifts while coasting
  • Prevention of “busy shifting”
  • Prevention of “transmission confusion” when drivers go into heavy acceleration, then suddenly lift their foot “change mind shift”

ZF 9-speed automatic

In addition, it can address conditions that cause the computer to record these errors:

  • P072F (stuck in fourth gear)
  • P076F (incorrect ration in seventh)
  • P0810 (clutch position control error)
  • P1CC9 (unable to engage gear)
  • P0734 (fourth gear incorrect ratio)
  • P071B (torque calculation performance error)

Sometimes, powertrain computers have been known to falsely record errors, and we do not know whether the issues above were caused by actual problems, solved by the software, or by false alarms.

The correct procedure should take around two hours, nearly all of which is a drive designed to train and test the transmission. Actually updating the flash should take around five to ten minutes, but the “adaptive drive learn,” which must be done by a skilled employee, takes much more time, and customers may want to observe the process to make sure this part is being done.

Customers are to be informed when the update is fully prepared, reportedly sometime in mid to late May.

Firmware updates for powertrain computers are not unusual, and can be issued long after a car is on the road.  As transmissions have become more complex and have gained additional gears — from four to nine in less than a decade — programming has become an ever-greater challenge for automakers. The ZF transmissions have the ability to handle dozens of shift maps, depending on conditions; for Cherokee, the situation is complicated by the addition of all wheel drive, as well.

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