Electronic Automatic Temperature Control

- Perform EATC On-Board Diagnostics. Record all error codes displayed during test.

- If error codes appear during EATC On-Board Diagnostics, follow diagnosis procedures outlined for each code recorded.

- If a condition exists but no error codes appear during the On-Board Diagnostics in Step 1, refer to Diagnosis When On-Board Diagnostics Indicates No Errors Found.

- The control assembly will detect electrical concerns occurring during the On-Board Diagnostics.

- Ensure that the engine is warm, at least 49°C (120°F) coolant temperature.

- To display the error codes for condition detection, initiate the On-Board Diagnostics by pushing OFF and FLOOR simultaneously and then AUTO within two seconds. The test may run as long as 20 seconds, during which time the display will be blank. If the display is blank for more than 20 seconds, go to EATC--When On-Board Diagnostics Indicates No Errors Found.

- The On-Board Diagnostics can be initiated at any time with the resulting error codes being displayed. Normal operation of the system stops when On-Board Diagnostics is activated. To exit the On-Board Diagnostics and restart the system, push the BLUE button. The On-Board Diagnostics should be deactivated before powering the system down. Refer to the Symptom Chart for an explanation of error codes.


- NOTE: The in-vehicle temperature should be greater than 50°F (10°C) for all error codes shown to be valid.

EATC CONTROL MODULE ERROR CODES

EATC System Concern

Possible Source(s):
- EATC control module damaged or inoperative.
- A/C air temperature control door damaged or inoperative.
- Sensor damaged or inoperative.

Action(s) to Take:
- Perform the following Diagnostics procedures and On-Board Diagnostics to register codes, then return to Symptom Chart for instructions.

01 (Code displayed during diagnostic procedures)

Possible Source(s):
- Damaged control assembly.

Action(s) to Take:
- Replace EATC Control Assembly.

02 (Code displayed during diagnostic procedures)

Possible Source(s):
- A/C air temperature control door damaged or inoperative.

Action(s) to Take:
- Refer to Pinpoint Test B. B: EATC Blend Door Actuator Functional Test

03 (Code displayed during diagnostic procedures)

Possible Source(s):
- Automatic temperature control sensor open or short.

Action(s) to Take:
- Refer to Automatic Temperature Control Sensor Diagnosis. ATC Sensor Diagnosis

04 (Code displayed during diagnostic procedures)

Possible Source(s):
- A/C ambient air temperature sensor and bracket open or short.

Action(s) to Take:
- Refer to A/C Ambient Air Temperature Sensor Diagnosis. A/C Ambient Air Temperature Sensor Diagnosis

05 (Code displayed during diagnostic procedures)

Possible Source(s):
- A/C sunload sensor short.

Action(s) to Take:
- Refer to A/C Sunload Sensor Diagnosis. A/C Sunload Sensor Diagnosis

888 (Code displayed during diagnostic procedures)

Possible Source(s):
- Temperature control lockout valve and switch inoperative.
- Vacuum System inoperative.
- A/C clutch inoperative or damaged.

Action(s) to Take:
- Refer to Pinpoint Test A. A: EATC System Inoperative, Intermittent, or Improper Operation

EATC DIAGNOSIS WHEN ON-BOARD DIAGNOSTIC INDICATES NO ERRORS FOUND

Cool Discharge Air When System is Set to AUTOMATIC and 90°F (32°C)

Possible Source(s):
- Heater system malfunction.

Action(s) to Take:
- Check coolant level. Check engine thermostat.

Possible Source(s):
- A/C air temperature control door not in max. heat position.

Action(s) to Take:
- Check position of A/C air temperature control door.
- Check A/C air temperature control door shaft attachment.
- Test per A/C Electronic Door Actuator Motor Diagnosis (assume DTC 02 was displayed in the On-Board Diagnostic). Refer to ATC Temperature Control Diagnosis/Pinpoint Tests. B: A/C ELECTRONIC DOOR ACTUATOR DIAGNOSIS

Warm Discharge Air in AUTOMATIC and 6O°F (16°C)

Possible Source(s):
- A/C clutch circuit malfunction.

Action(s) to Take:
- Test A/C clutch circuit per "EATC-- No A/C Clutch Operation Diagnosis." Refer to General System Diagnosis/Pinpoint Tests. F: Magnetic A/C Clutch Does Not Engage

Possible Source(s):
- Check refrigerant.

Action(s) to Take:
- Check Refrigerant System Pressures.

Possible Source(s):
- A/C air temperature control door not in MAX A/C position.

Action(s) to Take:
- Check position of A/C air temperature control door.
- Check A/C air temperature control door shaft attachment.
- Test per Vacuum Leak Diagnosis.
- Test per "EATC--A/C Electronic Door Actuator Motor Functional Diagnosis." (Assume 02 was displayed in the On-Board Diagnostic.) Refer to ATC Temperature Control Diagnosis/Pinpoint Tests. B: A/C ELECTRONIC DOOR ACTUATOR DIAGNOSIS

Cool Air in 85°F (29°C) Max. Heat in 90°F (32°C)

Possible Source(s):
- Sensor shorted.

Action(s) to Take:
- Troubleshoot according to Sensor Diagnosis. ATC Sensor Diagnosis

Heat in 65°F (18°C) Max. Cool in 60°F (16°C)

Possible Source(s):
- Sensor open.

Action(s) to Take:
- Troubleshoot according to Sensor Diagnosis. ATC Sensor Diagnosis

No A/C Blower Motor Operation

Possible Source(s):
- Damaged temperature control lockout valve and switch wiring.
- Damaged A/C blower motor speed control. Damage HI blower relay.
- Damaged control assembly.
- Damaged A/C blower motor.
- Damaged wiring.

Action(s) to Take:
- Test per "No Heater Blower Motor Operation". Refer to General System Diagnosis/Pinpoint Tests. A: Heater Blower Motor Does Not Run at Any Speed

High A/C Blower Motor Operation Only

Possible Source(s):
- Damaged control assembly.
- Damaged A/C blower motor speed control.
- Damaged wiring.

Action(s) to Take:
- Test per "High Heater Blower Motor Only". Refer to General System Diagnosis/Pinpoint Tests. B: Blower Motor In High In All Blower Motor Switch Positions

A/C Clutch is Engaged When System is Off

Possible Source(s):
- Damaged control assembly.
- Damaged wiring or interface components.

Action(s) to Take:
- Test according to EATC "A/C Clutch Does Not Disengage When In OFF Position.". Refer to General System Diagnosis/Pinpoint Tests. G: Magnetic A/C Clutch Does Not Disengage

Control Assembly Digits and VFD Do Not Light Up, A/C Blower Motor Off

Possible Source(s):
- Fuse.

Action(s) to Take:
- Replace fuse.

Possible Source(s):
- Ignition Circuit 298 open.

Action(s) to Take:
- Check Circuit 298.

Possible Source(s):
- Ignition Circuit 797 open.

Action(s) to Take:
- Check Circuit 797.

Possible Source(s):
- Ground Circuit 57A open.

Action(s) to Take:
- Check Circuit 57A.

Possible Source(s):
- Damaged control assembly.

Action(s) to Take:
- Replace control assembly.

Cold Air is Delivered During Heating When Engine is Cold

Possible Source(s):
- Damaged wiring.

Action(s) to Take:
- Place system at 9O°F/AUTOMATIC with ignition switch OFF. (Ignition switch must be OFF when grounding Circuit 244 for valid results). Ground Circuit 244 at temperature control lockout valve and switch. Start engine. If A/C blower motor is off, replace temperature control lockout valve and switch. If A/C blower motor is on, check wiring. If OK, replace control assembly.

Possible Source(s):
- Damaged or inoperative temperature control lockout valve and switch.

Action(s) to Take:
- Replace temperature control lockout valve and switch.

Control Assembly Temperature Display Will Not Switch From Fahrenheit To Celsius When the E/M Trip Computer Button is Pushed

Possible Source(s):
- Inoperative CCA switch module or control assembly.

CAUTION: Accidental shorting of the wrong pin could destroy the control assembly.

Action(s) to Take:
- Short Pin 20 of connector VA (Circuit 506) to ground. Turn ignition switch ON. If the display does not switch from F to C, Circuit 506 is open at the control assembly and the control assembly is damaged. Otherwise check the wiring and the tripminder.

System Does Not Control Temperature

Possible Source(s):
- Automatic temperature control sensor hose and elbow not connected to aspirator or automatic temperature control sensor.

Action(s) to Take:
- Inspect and service.

Possible Source(s):
- Aspirator not secured to A/C evaporator housing.

Action(s) to Take:
- Inspect and service.

Possible Source(s):
- Automatic temperature control sensor seal(s) missing or not installed properly.

Action(s) to Take:
- Inspect and service.

Possible Source(s):
- Aspirator or automatic temperature control sensor hose and elbow blocked with foreign material or kinked.

Action(s) to Take:
- Inspect and service.

Possible Source(s):
- Damaged aspirator hose.

Action(s) to Take:
- Inspect and service.

EATC Control Assembly Turns On and Off Erratically. No Control of System

Possible Source(s):
- Damaged charging system. EATC will not function with too low or too high battery voltage.

Action(s) to Take:
- Check battery voltage. If battery voltage is less than 10 volts or greater than 16 volts, refer to charging system. Do not replace EATC control assembly.