Accessing and Reading Diagnostic Trouble Codes

Harness Connector Faces:

Diagnostic Chart:

The CCR diagnostic system may be actuated by either of two methods. Grounding the Diagnostic Enable circuit at pin C of the [1][2]ALDL connector or by using the Control Module wiring harness connector. To read codes using the Control Module connector, ground pin D2 to pin D16.

Both driver select switch L.E.D.'s will blink in unison to transmit blink code diagnostics. Error codes can be read by counting the number of flashes of the L.E.D.'s. The error code display will start after pin D2 has been grounded for 3 seconds before beginning the blink code sequence. The sequence starts with a 3 second L.E.D. off period. Then code 12 is displayed three times to mark the beginning of the sequence. Next, each stored error code is blinked out in ascending order. Each code is displayed three times before proceeding to the next code. If the ground level signal remains applied to the test input (pins D2 and D16 remain connected), then the entire error code sequence repeats and starts by displaying the code 12 three times. If at any time the ground level signal is removed from the test input (pins D2 and D16 are disconnected), the sequence is aborted.

An example of an error code format is shown in image, (code 23 stored).