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Home >> Mazda >> 2016 >> CX-9 Sport, AWD >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Symptom Troubleshooting - Climate Control System >> No Temperature Control With Rear Climate Control Unit >> Diagnostic Procedure

Diagnostic Procedure

Step Inspection Action
1 INSPECT COOLANT TEMPERATURE 
  • Is the coolant sufficiently warmed up?
 Yes Go to the next step.
No Warm up the engine, then go to Step 24.
2* INSPECT FUSE 
 Yes Go to the next step.
No If the fuse is blown: 
  • Refer to the wiring diagram and verify whether or not there is a common connector between ROOM 25 A fuse and front climate control unit terminal/rear climate control unit terminal.

    If there is a common connector: 

    • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.
    • Repair or replace the malfunctioning part.

      If there is no common connector: 

    • Repair or replace the wiring harness which has a short to ground.
    • Replace the fuse.

    If the fuse is damaged: 

  • Replace the fuse.

Then go to Step 24.
3* INSPECT TO SEE WHETHER MALFUNCTION (OPEN CIRCUIT) IS IN B+ SIGNAL WIRING HARNESS (BETWEEN FUSE BLOCK AND REAR CLIMATE CONTROL UNIT) OR ELSEWHERE 
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between fuse block terminal and rear climate control unit terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness which has an open circuit.

Go to Step 24.
4* INSPECT TO SEE WHETHER MALFUNCTION IS IN REAR A/C UNIT OR REAR AIR MIX ACTUATOR 
 Yes Go to Step 22.
No Go to the next step.
5* INSPECT TO SEE WHETHER MALFUNCTION IS IN POSITION SENSOR OR ELSEWHERE 
  • Measure voltage at the following terminal (wiring harness-side) when rear airflow mode at VENT and HEAT.
    • Rear climate control unit terminal Q
  • Is voltage normal?
 Yes Go to Step 8.
No Go to the next step.
6* INSPECT TO SEE WHETHER MALFUNCTION (SHORT TO BATTERY POWER OR GROUND) IS IN POSITION SENSOR POWER SUPPLY OR ELSEWHERE 
  • Measure voltage at the following terminal (wiring harness-side).
    • Rear climate control unit terminal W
  • Is voltage approx. 5 V  ?
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between rear climate control unit terminal and rear air mix actuator/rear airflow mode actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness.

Go to Step 24.
7* INSPECT TO SEE WHETHER MALFUNCTION (SHORT TO POWER SUPPLY) IS IN POSITION SENSOR GROUND OR ELSEWHERE 
  • Measure voltage at the following terminal (wiring harness-side).
    • Rear climate control unit terminal O
  • Is the voltage below 1.0 V  ?
 Yes Refer to wiring diagram and inspect for open circuit following.
  • Between rear air mix actuator terminal A and junction point to rear airflow mode actuator (position sensor power supply).
  • Between rear air mix actuator terminal C and junction point to rear airflow mode actuator (position sensor ground).

Repair or replace the malfunctioning part or wiring harness.
Go to Step 24.
No Refer to the wiring diagram and verify whether or not there is a common connector between rear climate control unit terminal and rear air mix actuator/rear airflow mode actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness.

Go to Step 24.
8 INSPECT TO SEE WHETHER MALFUNCTION (SHORT TO POWER SUPPLY) IS IN WIRING HARNESS (REAR AIR MIX POSITION SIGNAL) OR ELSEWHERE 
  • Is the voltage B+  , at Step 4?
 Yes Refer to the wiring diagram and verify whether or not there is a common connector between rear climate control unit terminal and rear air mix actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to power supply.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness which has a short to power supply.

Go to Step 24.
No Go to the next step.
9 INSPECT REAR CLIMATE CONTROL UNIT CONNECTOR CONNECTION CONDITION 
 Yes Go to the next step.
No Reconnect the rear climate control unit connector properly.
Go to Step 24.
10 INSPECT REAR CLIMATE CONTROL UNIT CONNECTOR TERMINAL CONDITION 
 Yes Go to the next step.
No Repair/replace the connector or terminal.
Go to Step 24.
11 INSPECT REAR AIR MIX ACTUATOR CONNECTOR CONNECTION CONDITION 
 Yes Go to the next step.
No Reconnect the rear air mix actuator connector properly.
Go to Step 24.
12 INSPECT REAR AIR MIX ACTUATOR CONNECTOR TERMINAL CONDITION 
  • Disconnect the rear air mix actuator connector.

    Refer to REAR AIR MIX ACTUATOR REMOVAL/INSTALLATION .)

  • Inspect the connector and terminals (corrosion, damage, pin disconnection).
  • Are the connector and terminals normal?
 Yes Go to the next step.
No Repair/replace the connector or terminal.
Go to Step 24.
13* INSPECT TO SEE WHETHER MALFUNCTION (LACK OF CONTINUITY) IS IN WIRING HARNESS (REAR AIR MIX POSITION SIGNAL) OR ELSEWHERE 
  • Inspect continuity between the following terminals (wiring harness-side):
    • Rear climate control unit terminal S-rear air mix actuator terminal B
  • Is there continuity?
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between rear climate control unit terminal and rear air mix actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness.

Go to Step 24.
14* INSPECT TO SEE WHETHER MALFUNCTION (SHORT TO GROUND) IS IN WIRING HARNESS (REAR AIR MIX POSITION SIGNAL) OR ELSEWHERE 
  • Inspect for continuity between the following terminals (wiring harness-side) and body ground:
    • Rear climate control unit terminal S
  • Is there continuity?
 Yes Refer to the wiring diagram and verify whether or not there is a common connector between rear climate control unit terminal and rear air mix actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness.

Go to Step 24.
No Go to the next step.
15* INSPECT TO SEE WHETHER MALFUNCTION (OPEN CIRCUIT) IS IN POSITION SENSOR POWER SUPPLY OR ELSEWHERE 
  • Inspect for continuity between the following terminals (wiring harness-side) and junction point to rear airflow mode actuator (position sensor power supply).
    • Rear air mix actuator terminal A
  • Is there continuity?
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between rear air mix actuator terminal and junction point to rear airflow mode actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness which has an open circuit.

Go to Step 24.
16* INSPECT TO SEE WHETHER MALFUNCTION (OPEN CIRCUIT) IS IN POSITION SENSOR GROUND OR ELSEWHERE 
  • Inspect for continuity between the following terminals (wiring harness-side) and junction point to rear airflow mode actuator (position sensor ground).
    • Rear air mix actuator terminal C
  • Is there continuity?
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between rear air mix actuator terminal and junction point to rear airflow mode actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness which has an open circuit.

Go to Step 24.
17* INSPECT TO SEE WHETHER MALFUNCTION IS IN REAR AIR MIX ACTUATOR OR WIRING HARNESS (LACK OF CONTINUITY BETWEEN REAR CLIMATE CONTROL UNIT AND REAR AIR MIX ACTUATOR) 
 Yes Go to Step 21.
No Go to the next step.
18* INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (LACK OF CONTINUITY OR OPEN BETWEEN REAR CLIMATE CONTROL UNIT AND REAR AIR MIX ACTUATOR) OR ELSEWHERE 
  • Switch the ignition off.
  • Disconnect the negative battery terminal.

    Refer to NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)

  • Disconnect the rear climate control unit connector.

    Refer to REAR CLIMATE CONTROL UNIT REMOVAL/INSTALLATION .)

  • Inspect for continuity between the following terminals (wiring harness-side).
    • Rear climate control unit terminal G-rear air mix actuator terminal D (HOT motor drive signal)
    • Rear climate control unit terminal E-rear air mix actuator terminal E (COLD motor drive signal)
  • Is there continuity?
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between rear climate control unit terminal and rear air mix actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness.

Go to Step 24.
19* INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (SHORT TO B+ BETWEEN REAR CLIMATE CONTROL UNIT AND REAR AIR MIX ACTUATOR) OR ELSEWHERE 
  • Rear climate control unit and rear air mix actuator connectors are disconnected.
  • Connect the negative battery terminal.

    Refer to REAR CLIMATE CONTROL UNIT REMOVAL/INSTALLATION .)

  • Switch the ignition ON (engine off or on).
  • Measure voltage at the following terminals (wiring harness-side).
    • Rear climate control unit terminal G (HOT motor drive signal)
    • Rear climate control unit terminal E (COLD motor drive signal)
  • Are voltages approx. 0 V  ?
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between rear climate control unit terminal and rear air mix actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to power supply.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness which has a short to power supply.

Go to Step 24.
20* INSPECT TO SEE WHETHER MALFUNCTION IS IN WIRING HARNESS (SHORT TO GROUND BETWEEN REAR CLIMATE CONTROL UNIT AND REAR AIR MIX ACTUATOR) OR ELSEWHERE 
  • Switch the ignition off.
  • Rear climate control unit and rear air mix actuator connectors disconnected.
  • Inspect for continuity between the following terminals (wiring harness-side) and body ground.
    • Rear climate control unit terminal G (HOT motor drive signal)
    • Rear climate control unit terminal E (COLD motor drive signal)
  • Is there continuity?
 Yes Refer to the wiring diagram and verify whether or not there is a common connector between rear climate control unit terminal and rear air mix actuator terminal.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.
  • Repair or replace the malfunctioning part.

    If there is no common connector: 

  • Repair or replace the wiring harness which has a short to ground.

Go to Step 24.
No Go to the next step.
21 INSPECT REAR AIR MIX ACTUATOR 
 Yes Replace the rear climate control unit.
Refer to REAR CLIMATE CONTROL UNIT REMOVAL/INSTALLATION .)
Go to Step 24.
No Replace the rear air mix actuator.
Then go to Step 24.
Refer to REAR AIR MIX ACTUATOR REMOVAL/INSTALLATION .)
22 INSPECT REAR AIR MIX LINK 
  • Inspect the rear air mix links.

    Refer to REAR A/C UNIT REMOVAL/INSTALLATION .)

    • Is grease on link?
    • Are links securely and properly installed?
    • Are links free of obstructions and hindrances?
  • Are the above items normal?
 Yes Go to the next step.
No Apply grease to links.
If any links are damaged. Replace malfunctioning part.
Refer to REAR A/C UNIT DISASSEMBLY/ASSEMBLY .)
Then go to Step 24.
23 INSPECT REAR A/C UNIT AND REAR AIR MIX DOOR 
  • Inspect the rear A/C unit and rear air mix door.

    Refer to REAR A/C UNIT REMOVAL/INSTALLATION .)

    • Is door free of obstructions and damage?
    • Are doors securely and properly installed?
  • Are the above items normal?
 Yes Inspect the heater hoses.
  • If the heater hoses are not free of damage and cracks, repair or replace the heater hoses.
  • If the heater hose connections are loose, install securely in correct position.

Go to the next step.
No Remove the obstruction, or install door in proper position.
If any doors are cracked, replace them.
Refer to REAR A/C UNIT DISASSEMBLY/ASSEMBLY .)
Then go to the next step.
24 VERIFY THAT MALFUNCTION SYMPTOM DOES NOT RECUR AFTER REPAIR 
  • Does the unit operate at every temperature setting?
 Yes Troubleshooting completed.
Explain repairs to customer.
No Recheck malfunction symptoms, then repeat from Step1 if the malfunction recurs.
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