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Service bulletin 21-027-15

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id10150548
Published by NHTSA2018-12-10
Manufacturer's number21-027-15
Manufacturer's date2015-04-21
NHTSA componentELECTRICAL SYSTEM; POWER TRAIN

NHTSA's summary

Flash: Transmission Shift Enhancements This bulletin involves reprogramming of the Transmission Control Module (TCM) with the latest available software. A small number of customers may experience a Malfunction Indicator Lamp (MIL) Illumination. Upon further investigation, the technician may find Diagnostic Trouble Code (DTC) P0734 - Gear 4 Shift Incorrect Ratio stored in the TCM memory. In addition, the following TCM calibration improvements are also available for vehicles equipped with the 845RE 8 speed transmission (sales code DFL). These improvements are listed per engine application. 3.0L gas engine (sales code EHD) ? Improved upshift timing. ? Improved torque converter engagement. ? Improved shift timing during tow mode operation. ? Improved shift points during aggressive driving. ? Calibration improvement to correct bump feel during 2-1 downshift. ? Improved shift timing while in snow, base, and hill modes. 3.6L gas engine (sales code ERB) ? Improved 4-3 and 3-2 downshifts. ? Improved shift timing at higher altitudes. ? Improved shift timing while in sand mode. ? Calibration improvement for multi-gear downshift timing during passing maneuvers. ? Calibration improvement for intermittent delayed upshift.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Electrical system, Transmission and driveline

Trouble codes named

P0734

Vehicles listed
DODGE DURANGO2015
JEEP GRAND CHEROKEE2015

Listing a model year does not mean every vehicle of it is concerned: the document says which.

Recalls for the same vehicles and component
18V3320002018-05-17. ELECTRICAL SYSTEM:SOFTWARE; VEHICLE SPEED CONTROL:CRUISE CONTROL; ELECTRICAL SYSTEM:WIRING
20161842016-04-26. Powertrain
16V2400002016-04-25. POWER TRAIN:AUTOMATIC TRANSMISSION:CONTROL MODULE (TCM/PCM/TECM)

A recall listed here may apply to some of the same vehicles. Only the manufacturer can say whether it applies to one vehicle.

Other bulletins for the same vehicles and component
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S2621000003 REV.A2026-03-18. Service bulletin. The vehicle will exhibit a service transmission/check engine warning indicator for the following transmission models: 845RE, 8HP45, 850RE, 8HP50, 8HP70, 8HP75, 8HP75-PHEV, 8HP75-LCV, 8HP90, 8HP95. Transmissions may exhibit the following diagnostic codes: P07E4, P1DB2, P0716, P1B14, P0733, P1D90, P1DB7, P1B13.
S26080000102026-03-13. Service bulletin. Active Diagnostic Trouble Code (DTC) B1A10-00, B1A11-00, B1A12- 00, B1A13-00-, B1A14-00, B1A15-00, B1A16-00, and B1A17-00 in The Radio Frequency Hub (RFH)
1106032026-03-13. Service bulletin. SPEAKER - NONE
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91006712025-09-24. Service bulletin. Verify "Z" part number availability. Order a "Z" part number for all Exchange Orders: Warranty, Mopar, Customer pay and Service contract. Order "68" part number for New unsold units only.