Displaying & Reading Trouble Codes
DISPLAYING FAULTS AND READING FAULTS - ATC SYSTEMUse a scan tool to display DTCs stored in the A/C-heater control of the ATC system.
DISPLAYING FAULTS AND READING FAULTS - MTC SYSTEM
Use the A/C-heater control to display DTCs stored in the A/C-heater control of the MTC system. Begin testing the MTC system with the Lamp Test Mode, which checks for failed LED circuits that could prevent the system from correctly displaying DTCs. Once the Lamp Test Mode is completed and the LEDs of the MTC A/C-heater control illuminate correctly, enter the Display DTC Mode.
ENTERING LAMP TEST MODE - MTC SYSTEM
To enter the MTC system's Lamp Test Mode, perform the following:
NOTE: An active DTC 33 will prevent the control from entering diagnostic mode and performing certain diagnostic functions. It will also prevent proper A/C mode switch and status indicator function. If this occurs, refer to A/C HEATER CONTROL WILL NOT ENTER DIAGNOSTIC MODE (MTC) for the diagnostic test procedure.
1. Turn the ignition to the On position.
2. Turn the blower motor control (1) to the On position.
3. Press the A/C mode switch (2) down and turn the blower motor control to the Off position. Do not release the A/C mode switch until all of the LEDs
3. illuminate. If all LED indicators do not illuminate, repeat the entire procedure a second time to confirm indicator operation. If any LED fails to function as specified, replace the A/C-heater control.
4. To exit Lamp Test Mode, release the A/C mode switch.
ENTERING DISPLAY DTC MODE - MTC SYSTEM
To enter the MTC system's Display DTC Mode, perform the following:
NOTE: An active DTC 33 will prevent the control from entering diagnostic mode and performing certain diagnostic functions. It will also prevent proper A/C mode switch and status indicator function. If this occurs, refer to A/C HEATER CONTROL WILL NOT ENTER DIAGNOSTIC MODE (MTC) for the diagnostic test procedure.
1. Turn the ignition to the On position.
2. Turn the blower motor control (1) to the On position.
3. Press the A/C mode switch (2) down, turn the blower motor control to the Off position, wait three seconds and then release the A/C switch. The MTC system automatically switches from Lamp Test Mode to Display DTC Mode. If there are active or stored DTCs to display, the A/C status indicator (3) will begin to flash. If there are no active or stored DTCs to display, the LEDs on the A/C-heater control (4) will turn off and the system will automatically exit the mode of operation.
4. To manually exit Display DTC Mode, either turn the blower motor control to any speed setting, or turn the ignition off, or disconnect the negative battery cable from the battery.
DISPLAY SEQUENCING - MTC SYSTEM
MTC system DTCs will display in ascending numerical order but not in chronological order. Active DTCs will display before stored DTCs. If there are active and stored DTCs for the same parameter, the A/C-heater control will NOT display the stored DTC for that parameter. The EBL status indicator will illuminate and remain illuminated while the A/C-heater control is displaying stored DTCs. After displaying all active and stored, DTCs the A/C-heater control restarts at the beginning, displaying all DTCs again. To restart the sequence from the beginning while the A/Cheater control is displaying DTCs, press the EBL mode switch down, and then release it. This will cause the A/Cheater control to quit displaying the present code, turn off all LEDs for 2.0 seconds, and then it will begin flashing all DTCs again from the beginning.
READING DIAGNOSTIC TROUBLE CODES - MTC SYSTEM
Reading Diagnostic Trouble Codes - MTC System:
All active and stored DTCs for the MTC system have an assigned code number. The A/C status indicator flashes in a series of pulses to display the code numbers. The tens unit value (which is indicated with a long pulse) (1) is flashed first followed by the ones unit value (which is indicated with a short pulse) (2). The long pulse has an indicator on time of 0.80 seconds and the short pulse has an indicator on time of 0.2 seconds, with a 0.5 second indicator off-time between long and short pulses. When displaying multiple DTCs, the A/C status indicator will go off for two seconds (3) before displaying the next DTC. To indicate that the A/C-heater control has completed displaying all DTCs, the A/C status indicator will illuminate for two seconds and then go off for two seconds (4) before beginning to flash the DTCs over again.
STORED DTCs - ATC AND MTC SYSTEMS
The HVAC System Test provides a means for diagnosing stored DTCs.
The HVAC System Test consists of multiple diagnostic procedures which cover:
- A/C System Performance
- System Controls
- Air-door Functionality
Either perform the entire diagnostic procedure for a complete system test or perform an individual procedure if diagnosing a specific symptom.