almost complete EATC How to...

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There is more info to this than posted....of which you would need special tools to accomplish along with the rest of the procedures in the Maint Manual...but this should give you some pointers on Diagnosing problems with the EATC...Electronic Automatic Temperature Control Module


Electronic Automatic Temperature Control Module Self-Test
• The EATC module self-test will not detect concerns associated with data link messages like engine coolant temperature or vehicle speed signals. A scan tool must be used to retrieve these concerns.
• The EATC module self-test will detect concerns in the system control functions and will display hard diagnostic trouble codes (DTCs) in addition to intermittent diagnostic trouble codes for concerns that occur during system operation. The vehicle interior temperature should be between 4°-32°C (40°-90°F) when performing the self-test. If the temperatures are not within the specified ranges, false in-car temperature sensor DTCs will be displayed.
• The self-test can be initiated at any time. Normal operation of the system stops when the self-test is activated.
• To enter the self-test, press the OFF and FLOOR buttons simultaneously and then press the AUTOMATIC button within two seconds. The display will show a pulse tracer going around the center of the display window. The test may run as long as 30 seconds. Record all DTCs displayed.
• If any DTCs appear during the self-test, follow the diagnostics procedure given under ACTION for each DTC given.
• If a condition exists but no DTCs appear during the self-test, refer to the Symptom Chart Condition: The EATC System Is Inoperative, Intermittent or Improper Operation.
• To exit self-test and retain all intermittent DTCs, push the blue (cooler temperature) button. The control will exit self-test, retain all intermittent DTCs and then turn OFF (display blank).
• To exit self-test and clear all DTCs, press the DEFROST button. The vacuum fluorescent display window will show 888 and all function symbols for one second. Then, the EATC control assembly will turn OFF (display blank) and all DTCs will be cleared.
• Always exit the self-test before powering the system down (system turned OFF).
• Intermittent DTCs will be deleted after 80 ignition switch ON cycles after the intermittent condition occurs.

Powertrain Control Module Diagnostic Trouble Code (DTC) Index
DTC Description Action to Take
P1460 Wide open throttle A/C primary circuit malfunction Refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual ( OBDII Early release , OBDII-Bi-Fuel ).

P1464 A/C demand out of self-test range Refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual ( OBDII Early release , OBDII-Bi-Fuel ).

P1469 Low A/C cycling period Refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual ( OBDII Early release , OBDII-Bi-Fuel ).



Electronic Automatic Temperature Control (EATC) Module Diagnostic Trouble Code (DTC) Index
DTC EATC (Hard) Self-Test Faults EATC (Intermittent) Run-Time Faults Description Action to Take
B1249 024 022/25 Blend door failure or short Go To Pinpoint Test A .

B1251 031 N/A A/C in-car temperature sensor (19D888) open circuit Go To Pinpoint Test B .

B1253 030 N/A A/C in-car temperature sensor (19D888) short to ground Go To Pinpoint Test B .

B1255 041 043 A/C ambient temperature (19E702) sensor open circuit Go To Pinpoint Test C .

B1257 040 042 A/C ambient temperature sensor (19E702) short to ground Go To Pinpoint Test C .

B1261 050 052 A/C solar radiation sensor (19E663) circuit short to ground Go To Pinpoint Test D .

U1073 N/A — Standard Corporate Protocol (SCP) invalid or missing data for engine coolant Refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual ( OBDII Early release , OBDII-Bi-Fuel ).

U1341 N/A N/A Standard Corporate Protocol (SCP) invalid data for vehicle speed Refer to the Powertrain Control/Emissions Diagnosis (PC/ED) manual ( OBDII Early release , OBDII-Bi-Fuel ).




Symptom Chart

Condition Possible Sources Action
• No communication with the electronic automatic temperature control (EATC) module (19980) • Circuitry short/open. EATC module communication network. • Go To Pinpoint Test E .

• The EATC system is inoperative, intermittent or incorrect operation • Circuitry short/open. Input sensor(s)/erratic input signals. Charging system. Automatic temperature control sensor hose and elbow (19D888). • Go To Pinpoint Test F .

• Incorrect/erratic direction of airflow from outlet — manual climate control • No vacuum to the A/C control (19980). Function selector switch (19B888). Vacuum hose/kinked/pinched. Airflow door binding/stuck. Vacuum control motor (18A318). A/C vacuum check valve (19A563). A/C vacuum reservoir tank and bracket (19A566). Vacuum actuator arm not connected to the door crank. Heater control valve (18495) leaks vacuum. • Go To Pinpoint Test G .

• Incorrect/erratic direction of airflow from outlet — EATC • No vacuum to the A/C control (19980). Function selector switch (19B888). Vacuum hose/kinked/pinched. Airflow door binding/stuck. Vacuum control motor (18A318). A/C vacuum check valve (19A563). A/C vacuum reservoir tank and bracket (19A566). Vacuum actuator arm not connected to the door crank. Heater control valve (18495) leaks vacuum. Go To Pinpoint Test H .

• Insufficient, erratic, or no heat • Low engine coolant level. Engine overheating. Plugged or partially plugged heater core (18476). Temperature blend door binding/stuck. Temperature blend door actuator (19E616). Incorrect heater control valve (18495) operation. • Go To Pinpoint Test I .

• The air conditioning (A/C) is inoperative/does not operate correctly • Fuse(s). Circuitry short/open. A/C cycling switch (19E561). A/C system discharged/low charge. A/C pressure cutoff switch (19D594). A/C control (19980). • Go To Pinpoint Test J .

• The air conditioning (A/C) is always on • Circuitry short/open. A/C cycling switch (19E561). Function control switch (19B888). • Go To Pinpoint Test K .

• Insufficient air conditioning (A/C) cooling • Restricted A/C evaporator core orifice (19D990). Low refrigerant level. A/C cycling switch (19E561). Temperature blend door actuator control (19D816). A/C pressure cutoff switch (19D594). Incorrect heater control valve (18495) operation. • Go To Pinpoint Test L .

• No operation in all the temperature settings — manual climate control • Temperature blend door actuator control (19D816). Temperature blend door. Temperature blend door actuator motor (19E616). Circuitry open/shorted. • Go To Pinpoint Test M .

• The blower motor is inoperative — manual climate control • Circuitry open/shorted. A/C blower motor switch (19986). A/C blower motor resistor (19A706). A/C blower motor (19805). • Go To Pinpoint Test N .

• The blower motor is inoperative — EATC • Circuitry short/open. Blower motor relay (14N089). A/C blower motor (19805). A/C blower motor speed control (19E624). • Go To Pinpoint Test O .

• No operation in high blower setting — manual climate control • A/C blower motor resistor (19A706). A/C blower motor switch (19986). Go To Pinpoint Test P .

• No operation in lower speeds — manual climate control • Circuitry short/open. A/C blower motor resistor (19A706). A/C blower motor switch (19986). Blower motor relay (14N089). • Go To Pinpoint Test Q .

• The blower motor operates continuously in high speed — manual climate control • Circuitry short. A/C blower motor resistor (19A706). A/C blower motor switch (19986). Blower motor relay (14N089). • Go To Pinpoint Test R .

• The blower motor operates continuously in high speed — EATC • Circuitry short/open. A/C blower motor speed control (19E624). EATC module (19980). • Go To Pinpoint Test S .

• No operation in some blower speeds — EATC • A/C blower motor speed control (19E624). A/C blower motor (19805). EATC module (19980). • Go To Pinpoint Test T .

• The temperature set point does not repeat after turning the ignition switch OFF — EATC • Fuse(s). Circuitry short/open. EATC module (19980).CHECK circuit 729 (RD/WH) for a short or open and repair as necessary. If okay, INSTALL a new EATC module.

• The temperature display will not switch between Celsius and Fahrenheit — EATC • EATC module. PRESS the MAX A/C and DEFROST buttons simultaneously for at least 0.75 second. If the temperature display does not switch between Celsius and Fahrenheit, INSTALL a new EATC module.