Diagnostic Trouble Codes (DTCs) occur on vehicles when a sensor or component fails to perform its intended function or fails to communicate with the computer. The computer then sends out a Malfunction Indicator Lamp (MIL) and displays a check engine symbol on the instrument panel. To effectively reset the error code, the problem must first be diagnosed and corrected, if applicable, to prevent the MIL from continuing to be sent. Simply clearing the engine error codes on a Jeep Grand Cherokee will not fix the underlying problem. There are two procedures for clearing the error codes.
OBD II 1996 and newer
Open the driver’s door on the Jeep Grand Cherokee and locate the diagnostic link connector under the dash. It’s to the left of the steering wheel, uncovered and trapezoid-shaped.
Plug the OBD II scanner into the connector and then turn the ignition key to the power accessory position. This will illuminate all warning lights on the instrument panel without running the engine.
Check the scanner’s operating manual. Since so many companies make them, the operation of your specific scanner will be detailed in the manual. In general, running these scanners is easy and almost self-explanatory.
Scroll to the “erase codes” option displayed in the on-screen menu. Some scanners also have a delete button option. If so, press erase. If you had to scroll to the option, press the enter or submit button. Some scanners may ask if you are sure you want to erase the codes. If so, select “Yes.
Watch the scanner’s display screen until it reads “Command Sent” and then start the Grand Cherokee’s engine. Check the instrument panel to make sure the error code has been successfully cleared and the MIL is not still on.
OBD I 1993-1995
Open the hood of the Grand Cherokee.
Use a wrench to loosen the negative battery terminal clamp bolt and retaining nut.
Use a pair of channel lock pliers to twist the terminal clamp loose and lift it off the battery terminal.
Turn the headlight switch and ignition key to the auxiliary power position. This will expel any stored charge from the electrical system and clear the computer’s memory. Wait 10 minutes.
Turn the ignition key and headlight switch off, then reconnect the negative battery terminal clamp. Start the engine to make sure the fault code is cleared and the MIL is no longer illuminated.
Tips
While you can erase the codes on the Grand Cherokee OBD II by following Section 2 without using a scanner, it is not recommended on newer models. Most modern vehicles come with theft prevention radios and internal alarm systems. Once the computer’s memory is cleared, the vehicle will enter protection mode and also clear the radio and internal alarm systems, making them both inoperable. While they can be reprogrammed, getting the information will have to come from a Jeep dealer and will include a cost.
Most parts stores will read and offer to erase codes for you; although in some states, they are not allowed to erase codes, but may allow you to press the erase option on the scanner.
Once the error codes are erased, the computer needs to re-diagnose itself. It will relearn and communicate with all the sensors and circuits built into the system. This will take several drive cycles for the computer to communicate with all the sensors and circuits until it is in ready mode. This is when the computer will resend the MIL if it detects that the repair was not done on the Grand Cherokee. Clearing the codes to cheat the emissions tests will not work. The computer attached to the vehicle will be able to tell if the computer is in its ready mode and will fail until it is ready and the MIL stays off.
