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Pinpoint Test O: Temperature Control is Inoperative/Does Not Operate Correctly

WARNING: This page is about a different car, the 2005 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. O1 CHECK THE FEEDBACK POTENTIOMETER TOTAL RESISTANCE 
    • Disconnect: EATC Module C228a or EMTC Module C294a
    • Measure the resistance between EATC module C228A Pin 5 or EMTC module C294A Pin 5, circuit 243 (LG/OG) and EATC module C228A Pin 15 or EMTC module C294A Pin 15, circuit 247 (WH/YE).
      G04697314Courtesy of FORD MOTOR CO.
    • Is the resistance greater than 500 ohms? 
    1. YES  : Go to  O2.
    2. NO  : CARRY OUT the Blend Mode Door Actuator. If the actuator tests OK, REPAIR circuits 243 (LG/OG) and 247 (WH/YE) for a short together. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  2. O2 CHECK THE POTENTIOMETER LOW- AND HIGH-SIDE RESISTANCE 
    NOTE: Due to limited connector accessibility, before carrying out the mode door actuator component test, visually inspect the wiring between the HVAC module and actuator for opens or shorts. If no damage is visually evident, proceed with the test.
      Fig 1: Checking Potentiometer Low-Side Resistance
      GF0041066Courtesy of FORD MOTOR CO.
    • Measure the low-side  resistance between EATC module C228A Pin 15 or EMTC module C294A Pin 15, circuit 247 (WH/YE) and EATC module C228A Pin 18 or EMTC module C294A Pin 18, circuit 246 (VT).
      • Fig 2: Checking Potentiometer High-Side Resistance
      GF0041067Courtesy of FORD MOTOR CO.
    • Measure the high-side  resistance between EATC module C228a-5 or EMTC module C294a-5, circuit 243 (LG/OG) and EATC module C228a-18 or EMTC module C294a-18, circuit 246 (VT).
    • Are the resistances between 187 and 6,563 ohms? 
    1. YES  : Go to  O3.
    2. NO  : CARRY OUT the Blend Mode Door Actuator. If the actuator tests OK and if the low-side  resistance only is greater than 6,563 ohms, REPAIR circuit 247 (WH/YE) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

      If the low-side  resistance only is less than 187 ohms, REPAIR circuits 246 (VT) and 247 (WH/YE) for a short together. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

      If the high-side  resistance only is greater than 6,563 ohms, REPAIR circuit 243 (LG/OG) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

      If the high-side  resistance only is less than 187 ohms, REPAIR circuits 246 (VT) and 243 (LG/OG) for a short together. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

      If both the high-side and low-side  resistance is greater than 6,563 ohms, REPAIR circuit 246 (VT) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.

  3. O3 CHECK CIRCUITS 243 (LG/OG) AND 246 (VT) FOR A SHORT TO GROUND 
    • Disconnect: Blend Door Actuator C2092
      • Fig 3: Checking Circuits 243 (LG/OG) & 246 (VT) For A Short To Ground
      GF0041068Courtesy of FORD MOTOR CO.
    • Measure the resistance between ground and the following:
      • EATC Module C228A Pin 5 or EMTC module C294A Pin 5, circuit 243 (LG/OG).
      • EATC module C228A Pin 18 or EMTC module C294A Pin 18, circuit 246 (VT).
    • Is the resistance greater than 10,000 ohms? 
    1. YES  : Go to  O4.
    2. NO  : REPAIR circuit(s) for a short to ground. TEST the system for normal operation.
  4. O4 CHECK CIRCUITS 247 (WH/YE) AND 246 (VT) FOR A SHORT TO POWER 
    • Key in ON position.
      • Fig 4: Checking Circuits 247 (WH/YE) & 246 (VT) For A Short To Power
      GF0041069Courtesy of FORD MOTOR CO.
    • Measure the voltage between ground and the following:
      • EATC module C228A Pin 15 or EMTC module C294A Pin 15, circuit 247 (WH/YE).
      • EATC module C228A Pin 18 or EMTC module C294A Pin 18, circuit 246 (VT).
    • Is any voltage present? 
    1. YES  : REPAIR circuit(s) for a short to power. TEST the system for normal operation.
    2. NO  : Go to  O5.
  5. O5 CHECK THE DOOR ACTUATOR OPERATION 
    NOTE: If a jumper fuse opens while carrying out this test step, repair the circuit(s) for a short.
    • Connect: Blend Door Actuator C2092
      • Fig 5: Measuring Resistance Between EATC Module C228A-15 Or EMTC Module C294A-15
      GF0041066Courtesy of FORD MOTOR CO.
    • Measure the resistance between EATC module C228A Pin 15 or EMTC module C294A Pin 15, circuit 247 (WH/YE) and EATC module C228A Pin 18 or EMTC module C294A Pin 18, circuit 246 (VT).
      • Fig 6: Connecting Fused Jumper Wire Between EATC Module C228A-26 Or EMTC Module C294A-26
      GF0041070Courtesy of FORD MOTOR CO.
    • Connect a fused jumper wire between EATC module C228A Pin 26 or EMTC module C294A Pin 26, circuit 729 (RD/WH) and EATC module C228A Pin 7 or EMTC module C294A Pin 7, circuit 250 (OG).
      • Fig 7: Connecting Second Fused Jumper Wire Between EATC Module C228A-1 Or EMTC Module C294A-1
      GF0041071Courtesy of FORD MOTOR CO.
    • For no more than 2 seconds  , connect a second fused jumper wire between EATC module C228A Pin 1 or EMTC module C294A Pin 1, circuit 875 (BK/LB) and EATC module C228A Pin 6 or EMTC module C294A Pin 6, circuit 249 (DB/LG).
    • Remove the fused jumpers.
      • Fig 8: Connecting Fused Jumper Wire Between EATC Module C228A-1 Or EMTC Module C294A-1
      GF0041072Courtesy of FORD MOTOR CO.
    • Connect a fused jumper wire between EATC module C228A Pin 1 or EMTC module C294A Pin 1, circuit 875 (BK/LB) and EATC module C228A Pin 7 or EMTC module C294A Pin 7, circuit 250 (OG).
      • Fig 9: Connecting Second Fused Jumper Wire Between EATC Module C228A-26 Or EMTC Module C294A-26
      GF0041073Courtesy of FORD MOTOR CO.
    • For no more than 2 seconds  , connect a second fused jumper wire between EATC module C228A Pin 26 or EMTC module C294A Pin 26, circuit 729 (RD/WH) and EATC module C228A Pin 6 or EMTC module C294A Pin 6, circuit 249 (DB/LG).
    • Does the resistance smoothly increase and/or decrease when the jumpers are connected? 
    1. YES  : INSPECT for broken door and linkage. REPAIR as necessary. If the door and linkage are OK, go to  O7.
    2. NO  : Go to  O6.
  6. O6 CHECK THE ACTUATOR MOTOR DRIVE CIRCUITS FOR AN OPEN 
    • Disconnect: Blend Door Actuator C2092
      • Fig 10: Measuring Resistance Between EATC Module C228A-7 Or EMTC Module C294A-7
      GF0041074Courtesy of FORD MOTOR CO.
    • Measure the resistance between EATC module C228A Pin 7 or EMTC module C294A Pin 7, circuit 250 (OG) and blend door actuator C2092 Pin 6, circuit 250 (OG).
      • Fig 11: Measuring Resistance Between EATC Module C228A-6 Or EMTC Module C294A-6
      GF0041075Courtesy of FORD MOTOR CO.
    • Measure the resistance between EATC module C228A Pin 6 or EMTC module C294A Pin 6, circuit 249 (DB/LG) and blend door actuator C2092 Pin 1, circuit 249 (DB/LG).
    • Are the resistances less than 5 ohms? 
    1. YES  : INSPECT for binding or broken linkage. REPAIR as necessary. If no condition is found, INSTALL a new door actuator. TEST the system for normal operation.
    2. NO  : REPAIR the circuit(s) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
  7. O7 CHECK MODULE CONNECTION 
      NOTE: EATC only.
    • Clear the DTCs.
    • Carry out the HVAC Module Cold Boot Process.
      • NOTE: EATC only.
    • Carry out the HVAC Module - Electronic Automatic Temperature Control (EATC) On-Demand Self Test.
    • Operate the system.
    • Does the concern return? 
    1. YES  : INSTALL a new EATC or EMTC module. REFER to Climate Control System  article. TEST the system for normal operation.
    2. NO  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs.
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