Grounding the A and G will show codes from the ccm as well as the ecm, and will show the codes in the LCD display. If you only ground the A and B pins the check engine light will blink codes from the ecm but this will not tell you the codes from the ccm. The ccm is the computer that would flash the "sys" in the LCD.

To navigate through the ccm codes use the buttons "Trip/Odo" to go to the next diagnostic test(1.1, 1.2, 1.3, 1.4, 1.7, 4.0, 4.1, and 4.7), use "Range" to go to the previous test, use the "eng/met" to show the next value within each test(for example if there are more than one code stored in the system)use the "Inst/Aver" to go back within the test.

To display codes use tests 1.1 for ccm and 4.1 for ecm. Cycle through the tests with the "Trip/Odo" until the LCD displays the test you want, then cycle through the codes until you retreive them all. If in 1.1 it shows a c12 all codes are clear in the ccm. For other codes post the numbers. Tests 1.7 and 4.7 are used for clearing codes. 1.7 for the ccm and 4.7 for the ecm. after you are finished go to the code clearing tests and press and hold the Eng/Met until "---" is in the display. Good luck