33–A/C MODE SWITCH STUCK (MTC)





For a complete wiring diagram Refer to Section 8W.

Theory of Operation


The switch input changes when the switch is pushed down. A stored DTC 33 indicates that the A/C mode switch was stuck in a pushed position for more than 10 minutes, but has since returned to its normal state. An active DTC 33 indicates that the A/C mode switch is stuck in a pushed position. 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. For additional information about the A/C Heater Control's on-board diagnostics, refer to 24 - HEATING & AIR CONDITIONING - DIAGNOSIS AND TESTING.


  • When Monitored:

    With the ignition on.

  • Set Condition:

    If the A/C mode switch stays in a pushed position for more than 10 minutes.


Possible Causes
  
OBJECT HOLDING A/C MODE SWITCH IN A PUSHED POSITION
  
SUBSTANCE CAUSING A/C MODE SWITCH TO GET STUCK IN A PUSHED POSITION
  
(C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT SHORTED TO VOLTAGE
  
(C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT SHORTED TO (C121) SENSOR GROUND CIRCUIT
  
(C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT SHORTED TO GROUND
  
(C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT OPEN
  
A/C STATUS INDICATOR INOPERATIVE
  
A/C HEATER CONTROL
  



Diagnostic Test

1.INSPECT THE A/C HEATER CONTROL FOR DAMAGE




Is the A/C Heater Control damaged?

Yes


No
  • Go To 2

2.INSPECT FOR OBJECT OR SUBSTANCE CAUSING THE A/C MODE SWITCH TO STAY OR STICK IN A PUSHED POSITION



Is anything present that would cause the A/C mode switch to stay or stick in a pushed position?

Yes


No
  • Go To 3

3.CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT VOLTAGE







What is the voltage?

Below 4.8 Volts
  • Go To 4


Above 5.2 Volts
  • Go To 7


4.8 Volts To 5.2 Volts
  • Go To 8

4.CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO THE (C121) SENSOR GROUND CIRCUIT







Is the resistance below 10K ohms?

Yes


No
  • Go To 5

5.CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO GROUND





Is the resistance below 10K ohms?

Yes


No
  • Go To 6

6.CHECK (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR AN OPEN





Is the resistance below 5.0 ohms?

Yes


No

7.CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE








Is the voltage above 0.2 volts?

Yes


No

8.CHECK FOR NORMAL A/C MODE SWITCH & STATUS INDICATOR FUNCTION







Does the A/C status indicator turn on and off with respect to the switch position?

Yes
  • Go To 9


No

9.CHECK A/C HEATER CONTROL OPERATION BY ATTEMPTING TO ENTER DIAGNOSTIC MODE


  • Turn the blower control on.
  • Press the A/C mode switch down, turn the blower control to off, wait until both LEDs illuminate (approximately 5 seconds) and then release the A/C mode switch.



Did the A/C Heater Control enter diagnostic mode?

Yes


No