Troubleshooting Poor Shifting in Your Grand Cherokee

overdrive light
The Overdrive light will flash and provide your transmissions Fault Code. Getty

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 in the morning (or any of time of day for that matter, but when 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 only be 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. Is this an electronic or mechanical issue? We received the letter printed below recently, and I feel it sums of the Grand Cherokee transmission issue pretty well. I also provide some discussion after the letter to elaborate and help troubleshoot this reader's problem. Check it out, and hopefully be enlightened!

Marc writes:

I have a maintenance question on my 1995 Jeep Grand Cherokee's transmission. The problem started after a recent engine clean, water pump replacement, and a leaking transmission fluid cooling line was replaced. The problem is this: when I start the engine in the morning, the automatic transmission doesn't work, starts in third gear and no OD.

 

Manually selecting First or Second then Drive works okay, but still no OD. After the car has been sitting in the sun all day, the transmission works fine. I can tell if the problem is going to occur without even putting the car in gear by just watching the dash mounted "OD Off" light and/or pushing the OD Off button and seeing if the light toggles.

Under normal operation, the light turns on briefly upon starting the engine then extinguishes. When the problem occurs, the light randomly sticks on or off and won't toggle when the button is pressed.

Note that I live in Southern California, so it doesn't get very cold over night, maybe 60° F. The transmission fluid level is okay, so I'm guessing that there's moisture trapped in a connector somewhere in the engine bay. Would appreciate your advice.

  • 1995 Jeep Grand Cherokee Laredo
  • 4.0 liter
  • Automatic Transmission
  • 74,000 Miles
  • Fuel Injection
  • ABS brakes
  • P/S, A/C, Cruise control

Thanks,
Marc

Marc's description, and the helpful information he provides about the conditions both before and during the actual experience of the non-shifting problem, provide all the clues we need to troubleshoot this auto trans issue. Thankfully, since this is a '95 model, it's possible to retrieve DTCs (Diagnostic Trouble Codes) from the electronics that monitor the transmission.

The first thing we have to do is get the codes out of the Transmission Control Module. (Also, have you checked your transmission fluid level?) Diagnostic trouble flash codes are provided for diagnostic purposes. The lamp in the Overdrive Off Switch is used to signal the various flash codes.To view flash codes, proceed as follows:

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. 

  3. Flash codes will correspond to Powertrain Control Module codes in duration and spacing. 

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

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

Flashing Fault Codes for 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