WJdiag Pro is made for diagnosing issues of Jeep Grand Cherokee 2002-2004 year, WJ/WG models with 2.7 CRD engine. WJdiag is working with Bluetooth ELM327 device through OBD2. Supported functions of WJdiag Pro are listed on our website tutorial page at https://jeepswj.com/wjdiag-tutorial We highly recommend to use good ELM327 and avoid fake Chinese devices. Most of 10 EUR Chinese ELM327 devices do not support ISO 9141-2 and J1850 data protocols that are needed for Jeep WJ diagnostic and will display connection error even if some other generic diagnostic app can connect to some module. WJdiag is customized app for Jeep WJ/WG, it can not connect with your car if your ELM327 can not handle data that Jeep needs. There are no problems with good ELM327 devices and they can connect to car correctly. Your ELM327 compatibility can be checked with WJdiag Free. WJdiag has all options of professional car diagnostic - Fault Codes, Sensor Live Data, Tests and Coding. All electronic modules that 2.7 CRD Jeep has are supported. All electronic modules except Engine, Transmission and Shifter are supported on gasoline and 3.1 diesel model. In addition WJdiag Pro can access to many Chrysler Group cars made between 1998 and 2005. Electronic modules that WJdiag can access: Engine (2.7 CRD only), Transmission (2.7 CRD only), ABS, Airbag, Shifter Lever (2.7 CRD only), SKIM, Body Computer, Automatic Temp control, Driver Door, Passenger Door, Electro Mech Cluster, Overhead Console, Navigation System, Radio, CD Changer, Park Assist, Rain Sensor, Adjustable Pedal Module, Satellite Audio Receiver, Hands Free. Engine support for 2.7 CRD models: Fault codes reading with ID code and code explanation, Freeze Frame. Fault codes clearing Live Data (51 values, it is every value that 2.7 CRD engine has). Logging with options Input / Output (26 values - switches, EGR, relays, Steering Wheel etc.) Injector Test and Coding Transmission support for 2.7 CRD models: Fault codes reading with ID code and code explanation, Freeze Frame Fault codes clearing Live Data (22 values), Logging with options. Input / Output (23 values - solenoids, gears, Shifter signals, Transfer Case switch etc.) ABS support, all WJ/WG models: Fault codes reading and clearing Live Data, Logging with options Input/Output values Pinion Factor coding (Speedometer correction) Other control units randomly have Fault Codes, Live Data, Input/Output and tests. Before you buy our WJdiag Pro application, please try our WJdiag Free to confirm that your ELM327 diagnostic device can read data from your car.