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Climate Control: Diagnosis Honda Pilot II

Automatic HVAC System 6 illustrations ~428 words

Symptom Troubleshooting Index

SymptomDiagnostic procedureAlso check for
Rear mode control doors do not change between ceiling vents (cool) and floor vents (hot)See REAR MODE CONTROL MOTOR CIRCUIT TROUBLESHOOTINGClimate control unit DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blown fuse No. 36 (10A) in the under-dash fuse/relay box Poor or loose connections at the terminals
Voice communication does not workSee NAVIGATION COMMUNICATION LINE CIRCUIT TROUBLESHOOTINGClimate control unit DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Cleanliness and tightness of all terminals
Audio-HVAC does not display audio or climate control informationSee AUDIO COMMUNICATION LINE CIRCUIT TROUBLESHOOTINGClimate control unit DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Poor or loose connections at the terminals
Blower, heater controls, and A/C do not workSee CLIMATE CONTROL UNIT POWER, GROUND, AND COMMUNICATION CIRCUIT TROUBLESHOOTINGClimate control unit DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blown fuse No. 36 (10A) in the under-dash fuse/relay box Poor ground at G403 Poor or loose connections at the terminals
Both fans do not run at low speed with the A/C on (but the A/C compressor runs with the A/C on)See RADIATOR AND A/C CONDENSER FAN LOW SPEED CIRCUIT TROUBLESHOOTINGClimate control unit DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blown fuse No. 7 (30 A) in the under-hood fuse/relay box, and No. 36 (10 A) in the under-dash fuse/relay box Poor ground at G202*1,G201*2 Poor or loose connections at the terminals
The A/C condenser fan does not run at high speed (but both fans run at low speed and the A/C compressor operates with the A/C on)See A/C CONDENSER FAN HIGH SPEED CIRCUIT TROUBLESHOOTINGClimate control unit DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blown fuse No. 6 (30A) and No. 15 (7.5A) in the under-hood fuse/relay box Poor or loose connections at the terminals
Both fans do not run at high speed with the A/C on (but both fans run at low speed and the A/C compressor operates with the A/C on)ECT troubleshooting: ECT sensor 2 circuit low voltage (see DTC P2184: ECT SENSOR 2 CIRCUIT LOW VOLTAGE ), ECT sensor 2 circuit high voltage (see DTC P2185: ECT SENSOR 2 CIRCUIT HIGH VOLTAGE )Powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Poor or loose connections at the terminals
The A/C compressor clutch does not engage (but both fans run with the A/C on)See A/C COMPRESSOR CLUTCH CIRCUIT TROUBLESHOOTINGClimate control unit DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blown fuse No. 20 (7.5A) in the under-hood fuse/relay box, and No. 36 (10A) in the under-dash fuse/relay box Blower motor operation Poor or loose connections at the terminals
Blower fan(s) runs slower than expected in cold weatherECT troubleshooting: ECT sensor 2 circuit low voltage (see DTC P2184: ECT SENSOR 2 CIRCUIT LOW VOLTAGE ), ECT sensor 2 circuit high voltage (see DTC P2185: ECT SENSOR 2 CIRCUIT HIGH VOLTAGE ) NOTE: It is normal for the blower(s) to run slowly until the engine coolant temperature begins to rise. If the blower continues to run slowly for an abnormal length of time, continue to troubleshoot the problem.Powertrain DTCs (see GENERAL TROUBLESHOOTING INFORMATION ) Blower motor operation
HDS does not communicate with the climate control unit or the vehicleTroubleshoot the DLC circuit (see DLC CIRCUIT TROUBLESHOOTING )
Insufficient heatingCheck the coolant level (see COOLANT CHECK ) Check the radiator cap (see RADIATOR CAP TEST ) Check the operation of the air mix control motor and door (see FRONT AIR MIX CONTROL MOTOR TEST ) Check the coolant temperature Check the blower motor unit for obstructions Check for air leaks around the ducts and vents Check the inlet hose temperature If it is COLD, check for restrictions in the hose, a damaged or leaking thermostat, and a damaged or leaking water pump. If it is HOT, check for restrictions in the heater core. Back flush the heater core using standard commercially available equipment, or replace the heater core.Damaged cylinder head gasket
NOTE
It is normal for the blower(s) to run slowly until the engine coolant temperature begins to rise. If the blower continues to run slowly for an abnormal length of time, continue to troubleshoot the problem.

SYMPTOM TROUBLESHOOTING TABLE

Humidity Sensor Test

Note. Before testing, check for HVAC DTCs. (see GENERAL TROUBLESHOOTING INFORMATION )

Scheme 6

Scheme 6: Humidity Sensor Test
Scheme 6: Humidity Sensor Test

Scheme 7

Scheme 7
Scheme 7
  1. Remove the humidity/in-car temperature sensor (see «HUMIDITY/IN-CAR TEMPERATURE SENSOR REPLACEMENT»(ref-333598-S27883183462009072100000) ).
  2. Connect the humidity/in-car temperature sensor 4P connector.
  3. Turn the ignition switch to ON (II). Measure the voltage between the terminals with the (+) probe on terminal No. 2 and the (-) probe on terminal No. 3 with the connector connected.
  4. If the voltage is not as specified, replace the humidity/in-car temperature sensor (see «HUMIDITY/IN-CAR TEMPERATURE SENSOR REPLACEMENT»(ref-333598-S27883183462009072100000) ).

In-Car Temperature Sensor Test

Note. Before testing, check for HVAC DTCs. (see GENERAL TROUBLESHOOTING INFORMATION )

Scheme 8

Scheme 8: In-Car Temperature Sensor Test
Scheme 8: In-Car Temperature Sensor Test
  1. Remove the humidity/in-car temperature sensor (see «HUMIDITY/IN-CAR TEMPERATURE SENSOR REPLACEMENT»(ref-333598-S27883183462009072100000) ).
  2. Connect the humidity/in-car temperature sensor 4P connector.
  3. Test the humidity/in-car temperature sensor while holding it in front of the dashboard center vent. Measure the resistance with the system set to Max Cool. Measure the resistance with the system set to Max Hot.
  4. Compare the resistance reading between terminals No. 4 and No. 3 of the humidity/in-car temperature sensor with the specifications shown in the graph; the resistance should be within the specifications.
  5. If the resistance is not as specified, replace the humidity/in-car temperature sensor (see «HUMIDITY/IN-CAR TEMPERATURE SENSOR REPLACEMENT»(ref-333598-S27883183462009072100000) ).

Scheme 9

Scheme 9: Humidity/In-Car Temperature Sensor Replacement
Scheme 9: Humidity/In-Car Temperature Sensor Replacement
  1. Remove the driver's dashboard lower cover (see «DRIVER'S DASHBOARD LOWER COVER REMOVAL/INSTALLATION»(ref-333587-S27385002872009072100000) ).
  2. Remove the humidity/in-car temperature sensor (A) from the dashboard lower cover. If needed, remove the self-tapping screws and adapter (B).
  3. Install the sensor in the reverse order of removal. Be sure to connect the air hose securely.

Sunlight Sensor Test

Note. Before testing, check for HVAC DTCs. (see GENERAL TROUBLESHOOTING INFORMATION )

Scheme 10

Scheme 10: Sunlight Sensor Test
Scheme 10: Sunlight Sensor Test
  1. Remove the sunlight sensor from the dashboard (see «SUNLIGHT SENSOR REPLACEMENT»(ref-333598-S32468842152009072100000) ).
  2. Connect the sunlight sensor 5P connector.
  3. Turn the ignition switch to ON (II). Measure the voltage between the terminals with the (+) probe on No. 4 terminal and the (-) probe on No. 2 terminal with the connector connected. NOTE: The voltage readings will not change under the light of a flashlight or a fluorescent lamp. Voltage should be: 3.6-3.7 V or more with the sensor out of direct sunlight. 3.3-3.5 V or less with the sensor in direct sunlight.
  4. If the voltage is not as specified, replace the sunlight sensor (see «SUNLIGHT SENSOR REPLACEMENT»(ref-333598-S32468842152009072100000) ).

Scheme 11

Scheme 11: Sunlight Sensor Replacement
Scheme 11: Sunlight Sensor Replacement
  1. Remove the sunlight sensor (A) from the dashboard, then disconnect the 5P connector (B). Be careful not to damage the sensor and the dashboard.
  2. Install the sensor in the reverse order of removal.

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