How to Troubleshoot the Heating
How to Check for DTCs with the HDS
  1. Make sure the ignition switch to LOCK (0).
  1. Connect the HDS to the data link connector (DLC) (A) located under the driver's side of the dashboard.
  1. Turn the ignition switch to ON (II).
  1. Make sure the HDS communicates with the vehicle and the climate control unit. If it doesn't, troubleshoot the DLC circuit, R20A3 engine model, or K24Z3 engine model.
  1. Select HVAC/CLIMATE CONTROL in the BODY ELECTRICAL menu.
  1. Select DTCs in the HVAC/CLIMATE CONTROL menu.
  1. Check for DTCs. If any DTCs are indicated, write down the DTCs, then go to the indicated DTC troubleshooting. If no DTCs are indicated, refer to symptom troubleshooting.
    NOTE:
    • After troubleshooting, clear the DTCs with the HDS.
    • For specific operations, refer to the user's manual that came with the HDS.
How to Use the Self-diagnostic Function with the HDS
  1. Make sure the ignition switch to LOCK (0).
  1. Connect the HDS to the data link connector (DLC).
  1. Turn the ignition switch to ON (II).
  1. Make sure the HDS communicates with the vehicle and the climate control unit. If it doesn't, troubleshoot the DLC circuit, R20A3 engine model, or K24Z3 engine model.
  1. Select HVAC/CLIMATE CONTROL in the BODY ELECTRICAL menu.
  1. Select INSPECTION in the HVAC/CLIMATE CONTROL menu.
  1. Select CLIMATE CONTROL SELF TEST in the INSPECTION menu.
  1. Check for DTCs. If any DTCs are indicated, write down the DTCs, then go to the indicated DTC troubleshooting.
    NOTE:
    • After troubleshooting, clear the DTCs with the HDS.
    • For specific operations, refer to the user's manual that came with the HDS.
How to Use the Self-diagnostic Function without the HDS
The heater control unit has a self-diagnostic function. To run the self-diagnostic function, do the following:
  1. Turn the ignition switch to LOCK (0) and then to ON (II).
  1. Press and hold the OFF button, then within 10 seconds press and release the REAR WINDOW DEFOGGER/MIRROR DEFOGGER button five times. Release the OFF button; then the self-diagnostic begins.
    NOTE:
    • The blower motor will run at various speeds regardless of what the panel is displaying.
    • If there is a problem with the system, it will flash 88 and AUTO, 88 and A/C ON, or 88 AUTO and 88 A/C ON, and one or more of the 14 indicator segments (A through P). Refer to checking for DTCs.
    • If there is more than one DTC, they are displayed one at a time in sequence followed by a pause (all the display indicator segments illuminate) between the DTCs.
    • If there are no problems detected, the segments will not illuminate, and the system will appear to be turned off.

Canceling the Self-diagnostic Function

  1. Turn the ignition switch to LOCK (0) to cancel the self-diagnostic function. After completing repair work, run the self-diagnostic function again to make sure that there are no other DTCs.
Checking for DTCs
The temperature display indicates single or multiple DTCs. If no DTCs are present, the indicator remains blank.
NOTE: If indicator segments A, C, D, E, K, with the AUTO indicator, or the A/C ON indicator are on at the same time, there may be an open in the common ground wire.
DTC (Driver's Temperature Indicator Segment, AUTO, and A/C Indicator)
Detection Item
A and AUTO
B and AUTO
C and AUTO
D and AUTO
E and AUTO
F and AUTO
A and A/C ON
B and A/C ON
C and A/C ON
D and A/C ON
E and A/C ON
F and A/C ON
G and A/C ON
H and A/C ON
J and A/C ON
K and A/C ON
L and A/C ON
M and A/C ON
N and A/C ON
A
B
Output shaft (countershaft) speed sensor signal error. Check for DTCs in the A/T system and go to the indicated DTC's troubleshooting. If no DTCs are found, replace the heater control unit
C
Engine coolant temperature (ECT) sensor signal error. Check for DTCs in the PGM-FI system and go to the indicated DTC's troubleshooting. If no DTCs are found, replace the heater control unit
D
Communication bus line error (bus-off)


Displaying Sensor Inputs at the Heater Control Unit
The heater control unit has a mode that displays sensor inputs it receives. This mode shows you what the heater control unit is receiving from each of the sensors, one at a time, and it can help you determine if a sensor is faulty.
Check these items before using the sensor input display mode
  1. Turn the ignition switch to ON (II), and check the recirculation door function; press the recirculation button to switch from FRESH to RECIRC. The air volume and sound should change slightly.
  1. Set the temperature using the driver's control switch to the desired test temperature:
    • Press AUTO button on, the LED turns on.
    • Press DUAL button off, the LED turns off.
    When selecting the test temperature, note these items:
    • ‘‘Lo'' temperature setting will default to MAX COOL, VENT, and RECIRC.
    • ‘‘Hi'' temperature setting will default to MAX HOT, HEAT, and FRESH.
    • 16 through 28 °C settings will use the automatic heater control logic. (Except KQ model)
    • 19 through 31 °C settings will use the automatic heater control logic. (KQ model)
  1. Turn the ignition switch to LOCK (0).
To run the sensor input display mode, follow these steps
  1. Turn the ignition switch to LOCK (0).
  1. Press and hold both the AUTO and RECIRCULATION CONTROL buttons, then start the engine.
  1. After the engine starts, release both buttons. The display panel control unit will flash the sensor number and then the value for that sensor. Record the value displayed.
  1. To advance to the next sensor, press the REAR WINDOW DEFOGGER button.
    Sensor
    Item
    Displayed Value
    1
    Mode Positioning
    %
    2
    In-car Temperature
    °C
    3
    Outside Air Temperature
    °C
    4
    Solar Radiation Sensor Value: Dark = 00, Flashlight = 04, Cloudy = 10, Sunny = 65
    10 kcal/m 2 ·h
    6
    Driver's Air Mix Opening (Low value indicates cooler air distribution, higher value indicates warmer air distribution)
    % of opening
    7
    Passenger's Air Mix Opening (Low value indicates cooler air distribution, higher value indicates warmer air distribution)
    % of opening
    8
    Recirculation Control Opening
    % of opening
    9
    Vehicle Speed (Vehicle must be driven to display speed)
    10 km/h
    A
    Engine Coolant Temperature
    °C
    b
    Vent Temperature Air Out (TAO)
    °C

    NOTE:
    • The sensor values will be displayed in degrees Celsius (°C) or an alphanumeric code. Use the chart to convert the value to degrees Fahrenheit (°F).
    • If the sensor value displays ‘‘Er'' this indicates there is an open or short in the circuit or sensor. Check for DTCs using the HDS, or refer to checking DTCs by DTC indication.
    • If necessary, compare the sensor input display to a known-good vehicle under the same test conditions.
    • If the sensor is out of the normal range, refer to the sensor test or substitute a known-good sensor, and recheck.
  1. To cancel the sensor input display mode, press the AUTO button or turn the ignition switch to LOCK (0).