Pinpoint Test I: The Electronic Automatic Temperature Control (EATC) Module Does Not Respond To The Diagnostic Tool

WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Use the correct probe adaptor(s) when making measurements. Failure to use the correct probe adaptor(s) may damage the connector.

I1 CHECK THE EATC MODULE C228B FOR DAMAGE
- Key in OFF position.
- Disconnect: EATC Module C228b.
- Inspect the EATC module C228b for damage.
- Is the EATC module C228b OK?
- Yes : GO to I2.
- No : REPAIR the EATC module C228b. CARRY OUT the diagnostic tool data link test.
I2 CHECK THE EATC MODULE GROUND CIRCUIT FOR AN OPEN
- Measure the resistance between the DATC module C228b-2, circuit 1203 (BK/LB) and ground.
  
  Fig 1: Measuring Resistance Between DATC Module C228b-2, Circuit 1203 (BK/LB) And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : GO to I3.
- No : REPAIR the circuit. CLEAR the diagnostic trouble codes (DTCs). REPEAT the self-test. CARRY OUT the diagnostic tool data link test.
I3 CHECK THE CAN CIRCUITS BETWEEN THE EATC MODULE AND THE DLC FOR AN OPEN
- Measure the resistance between the EATC module C228b-11, circuit 3126 (TN/YE), harness side and the data link connector (DLC) C251-6, circuit 3126 (TN/YE), harness side.
  
  Fig 2: Checking CAN Circuits Between EATC Module And DLC For An Open
  Courtesy of FORD MOTOR CO.
- Measure the resistance between the EATC module C228b-1 circuit 3125 (RD/YE), harness side and the DLC C251-14, circuit 3125 (RD/YE), harness side.
  
  Fig 3: Measuring Resistance Between EATC Module C228b-1 Circuit 3125 (RD/YE) And DLC C251-14
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : GO to I4.
- No : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the diagnostic tool data link test.
I4 CHECK THE EATC MODULE VOLTAGE CIRCUIT 1050 (LG/VT) FOR AN OPEN
- Key in ON position.
- Measure the voltage between the DATC module C228b-3, circuit 1050 (LG/VT) and ground.
  
  Fig 4: Measuring Voltage Between DATC Module C228b-3, Circuit 1050 (LG/VT) And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to I5.
- No : VERIFY the central junction box (CJB) fuses 30 (5A) is OK. If OK, REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the diagnostic tool data link test.
I5 CHECK THE EATC MODULE VOLTAGE CIRCUIT 729 (RD/WH) FOR AN OPEN
- Measure the voltage between the DATC module C228b-13, circuit 729 (RD/WH) and ground.
  
  Fig 5: Measuring Voltage Between DATC Module C228b-13, Circuit 729 (RD/WH) And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to I6.
- No : VERIFY the battery junction box (BJB) fuses 15 (15A) is OK. If OK, REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the diagnostic tool data link test.
I6 CHECK FOR CORRECT EATC MODULE OPERATION
- Disconnect all the EATC module connectors.
- Check for:
  - corrosion
  - push-out pins
- Connect all the EATC module connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
- Yes : INSTALL a new EATC module. REFER to CLIMATE CONTROL SYSTEM-GENERAL INFORMATION . CLEAR the DTCs. REPEAT the self-test. CARRY OUT the diagnostic tool data link test.
- No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. CARRY OUT the diagnostic tool data link test.