Diagnosing Shifting Problems on a Jeep Grand Cherokee

Jeep 4X4 on dirt road at dusk, Canada
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There is a common issue with shifting on a number of Jeep Grand Cherokee models as they get older and their mileage gets high. The shifting problems usually surface when the vehicle is first started and the engine and transmission are cold.  Often, you'll still be able to drive the vehicle, but it will only operate in one or two of the gears. For example, you may find that you're only able to drive the car in the automatic transmission's 3rd gear, only being able to select the other two gears when you shift the transmission manually.

The most common cause of transmission problems is the easiest to fix: check the fluid level in the transmission and restore it to the proper levels. Very often, this will solve the problem. But Jeep Grand Cherokees seem especially prone to more serious transmission problems, and some owners are quite perplexed at their inability to determine the causes. 

On models with OBD (onboard diagnostics) systems, a code scanner plugged into the diagnostic port will give you a reading that helps identify the problem. There is also an easier way to do this if you don't have a code reader, described below. 

How to view Transmission Diagnostic Flash Codes 

  1. Turn ignition key ON and OFF three times, finally leaving the key in the ON position. Leave the Overdrive Off Switch in the normal overdrive (ON) position. 

  2. Immediately begin counting the number of flashes displayed by the Overdrive Off Switch indicator lamp. There will be two sets of flashes, separated by a pause. The number of flashes in each group indicates the first and second digit in the flash codes.

  1. A code 55 identifies the end of flash code transmission.

How to Interpret Transmission Diagnostic Flash Codes 

Below, you'll find the list of Transmission Fault Codes for Jeep Automatic Transmissions.

Code 11 - No Engine Speed Sensor Signal
Code 12 - No Output Shaft Sensor Signal
Code 13 - No Vehicle Speed Sensor Signal
Code 14 - Governor Pressure Sensor Signal
Code 15 - Throttle Position Signal
Code 16 - Transmission Temperature Sensor
Code 17 - Overdrive Off Switch Circuit
Code 18 - System Voltage Out of Limits
Code 19 - Standby Voltage Out of Limits
Code 21 - Governor Pressure Solenoid Circuit
Code 22 - 3-4 Solenoid Circuit
Code 23 - Torque Converter Clutch Circuit
Code 24 - Overdrive Off Lamp Circuit
Code 25 - EEPROM Checksum Error
Code 26 - Governor Pressure Sensor Offset Drift
Code 55 - End of Message

You may or may not be skilled enough to actually fix the problems indicated by the flash codes, but you will now have an understanding of where the issue lies in order to seek help from a mechanic.