Join Date: Sep 2003
Location: Northern VA, USA
Extracting Fault Codes:
Turn the ignition switch ON, OFF, ON, OFF, ON and observe the CHECK ENGINE LIGHT. The CHECK ENGINE LIGHT should begin to flash a series of codes. The flashes will be separated by short and long pauses. The long pauses separate the "ones" and "tens" positions, and each code from the next. A code 55 will be displayed at the end of the test.
Here is another method that I found on the web
Extracting Fault Codes OBDII
Newer (OBDII) models - Put the key into the ignition, push down the odometer reset button, then turn the key to RUN with your finger on the button - and then release the button. The odometer will go through 1111111 through 999999, and then display the car's serial number. It will then show the error codes (it might show them starting with P). If this method does not work, try the OBDI method.
94 Black Laredo 4-Liter with QuadraTrac (42RE trans & NP249 TC) 200,000 + miles purchased new
88 Cherokee 2-door with 5speed manual 139K miles(deceased) purchased new