Retrieving Diagnostic Trouble Codes (DTC)

Retrieving Diagnostic Trouble Codes (DTC)
The diagnostic mode is made up of the three following separate steps:
1. Tone and door ajar lamp test
2. Trouble code test
3. Input test
Step 1 is run immediately upon entry into the diagnostic mode.
Step 2 is run without the key in the ignition.
Step 3 is run with the key in the ignition.
The operator may switch between Steps 2 and 3 indefinitely until the diagnostic mode input is ungrounded.

Step 1 - Tone and Door Alar Lamp Test
When the diagnostic mode is first entered, the CTM will generate a tone and light the door ajar lamp for three seconds. If the key is in the RUN or ACCY position, use the following table to diagnose problems entering the diagnostic mode. After the three-second test, the CTM will pause for one-second and then proceed to either Step 2 or Step 3 depending on whether the key is in the ignition.

The diagnostic mode is used to test the central timer module (CTM) and associated connections while the CTM is in the vehicle. While in this mode, the technician can retrieve and clear the internally stored trouble codes and also individually test each of the CTM inputs. The normal CTM functions are disabled while in the diagnostic mode. The wiper functions are also disabled while in the diagnostic mode. The wiper motor output is operated by the washer switch input during the input test to allow testing of the wiper motor status switch input.

Step 2 - Trouble Code Output
When the CTM is in the normal mode of operation, it is continually monitoring itself. When a fault occurs it is recorded. The trouble code output mode shows these codes, if any, to the technician by flashing the door ajar lamp and simultaneously sounding the chime in a certain order. These codes may then be used to help diagnose potential intermittent failures.

Step 3 - Input Test
The input test allows an operator to individually test the CTM inputs. It is entered when the operator puts the key in the ignition. The inputs may be cycled in any order. As an input is toggled on or off, the door ajar lamp and tone outputs will be activated for one second for confirmation. At any time, if the key is removed from the ignition assembly, the trouble code output will be re-entered.