DTC P1777 (P0773): Reduction solenoid valve system <5A/T>: Diagnosis

Required Special Tools: 

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)
  • MB991824: V.C.I.
  • MB991827: M.U.T.-III USB Cable
  • MB991910: M.U.T.-III Main Harness A

1. STEP 1. Using scan tool MB991958, check actuator test item 5: Reduction Solenoid Valve. 
   CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
   1. Connect scan tool MB991958 to the data link connector.
   2. Turn the ignition switch to the "ON" position.
   3. Set scan tool MB991958 to the actuator test mode.
      • Item 5: Reduction Solenoid Valve.
        • An audible clicking or buzzing should be heard when the reduction solenoid valve is energized.
   4. Turn the ignition switch to the "LOCK" (OFF) position.

      Q: Is the solenoid valve operating properly? 

      1. YES:  It can be assumed that this malfunction is intermittent. Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS .
      2. NO:  Go to Step 2.
         Fig 1: Connecting Special Tool MB991910 To Data Link Connector

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2. STEP 2. Using scan tool MB991958, read the A/T diagnostic trouble code. 
   1. Connect scan tool MB991958 to the data link connector.
   2. Turn the ignition switch to the "ON" position.
   3. Check for A/T diagnostic trouble code.
   4. Turn the ignition switch to the "LOCK" (OFF) position.

      Q: Is DTC P1788 (P1751) set? (DTC P1788 (P1751) may be set along with multiple DTCs). 

      1. YES:  Refer to DTC P1788 (P1751): A/T CONTROL RELAY SYSTEM .
      2. NO:  Go to Step 3.
         Fig 2: Connecting Special Tool MB991910 To Data Link Connector

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3. STEP 3. Using scan tool MB991958, read the A/T diagnostic trouble code. 
   1. Connect scan tool MB991958 to the data link connector.
   2. Turn the ignition switch to the "ON" position.
   3. Check for A/T diagnostic trouble code.
   4. Turn the ignition switch to the "LOCK" (OFF) position.

      Q: Are DTC P1778 (P0743) and DTC P1773 (P0753) set? (Multiple DTCs may be set). 

      1. YES:  Go to Step  8.
      2. NO:  Go to Step 4.
         Fig 3: Connecting Special Tool MB991910 To Data Link Connector

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4. STEP 4. Measure the Reduction solenoid valve resistance at A/T control solenoid valve assembly connector B-111. 
   1. Disconnect connector B-111 and measure at the solenoid valve side.
      Fig 4: Locating A/T Control Solenoid Valve Assembly Connector B-111

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   2. Measure the resistance between solenoid valve assembly connector B-111 terminals 8 and 10.

      Resistance value: 2.7-3.4 Ω [at 20°C (68°F)] 

      Q: Is the measured resistance 2.7-3.4 Ω [at 20°C (68°F)]? 

      1. YES:  Go to Step  6.
      2. NO:  Go to Step 5.
         Fig 5: Measuring Resistance Between Solenoid Valve Assembly Connector B-111 Terminals 8 And 10

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5. STEP 5. Measure the solenoid valve resistance at the reduction solenoid valve assembly inside the transaxle. 
   1. Disconnect connector B-111-6 and measure at the solenoid valve side.
      Fig 6: Locating Solenoid Valve Connector B-111-6

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   2. Measure the resistance between Reduction solenoid valve terminals 1 and 2.

      Resistance value: 2.7-3.4 Ω [at 20°C (68°F)] 

      Q: Is the measured resistance 2.7-3.4 Ω [at 20°C (68°F)? 

      1. YES:  Replace the harness wire between A/T control solenoid valve assembly connector B-111 and the solenoid valves.
      2. NO:  Replace the Reduction solenoid valve. Refer to VALVE BODY .
         Fig 7: Measuring Resistance Between Reduction Solenoid Valve Terminals 1 And 2

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6. STEP 6. Check PCM connector B-20 and A/T control solenoid valve assembly connector B-111 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Are the connectors and terminals in good condition? 

   1. YES:  Go to Step 7.
   2. NO:  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
      Fig 8: Locating PCM Connector B-20

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      Fig 9: Locating A/T Control Solenoid Valve Assembly Connector B-111

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7. STEP 7. Check the harness for an open or short circuit to ground between PCM connector B-20 terminal 55 and A/T control solenoid valve assembly connector B-111 terminal 5. 

   Q: Is the harness wire in good condition? 

   1. YES:  Replace the PCM. When the PCM is replaced, register the encrypted code. Refer to ENCRYPTED CODE REGISTRATION CRITERIA TABLE .
   2. NO:  Repair or replace the harness wire.
      Fig 10: Locating PCM Connector B-20

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      Fig 11: Locating A/T Control Solenoid Valve Assembly Connector B-111

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8. STEP 8. Measure the supply voltage at A/T control solenoid valve assembly connector B-111. 
   1. Disconnect solenoid valve assembly harness connector B-111.
   2. Turn the ignition switch to the "ON" position.
      Fig 12: Locating A/T Control Solenoid Valve Assembly Connector B-111

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   3. Measure the voltage between harness connector B-111 terminal 10 and ground.
      • The voltage should equal battery positive voltage.
   4. Turn the ignition switch to the "LOCK" (OFF) position.

      Q: Is the measured voltage battery positive voltage? 

      1. YES:  Go to Step  11.
      2. NO:  Go to Step 9.
         Fig 13: Measuring Voltage Between Harness Connector B-111 Terminal 10 And Ground

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9. STEP 9. Check A/T control relay connector B-15X in the engine component relay box and A/T control solenoid valve assembly connector B-111 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Are the connectors and terminals in good condition? 

   1. YES:  Go to Step 10.
   2. NO:  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
      Fig 14: Locating A/T Control Relay Connector B-15X

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      Fig 15: Locating A/T Control Solenoid Valve Assembly Connector B-111

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10. STEP 10. Check the harness for an open circuit or short circuit to ground between A/T control relay connector B-15X terminal 4 in the engine component relay box and A/T control solenoid valve assembly connector B-111 terminal 10. 

    Q: Is the harness wire in good condition? 

    1. YES:  Go to Step 11.
    2. NO:  Repair or replace the harness wire.
       Fig 16: Locating A/T Control Relay Connector B-15X

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       Fig 17: Locating A/T Control Solenoid Valve Assembly Connector B-111

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11. STEP 11. Check PCM connector B-20 and A/T control solenoid valve assembly connector B-111 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

    Q: Are the connectors and terminals in good condition? 

    1. YES:  Go to Step 12.
    2. NO:  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
       Fig 18: Locating PCM Connector B-20

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       Fig 19: Locating A/T Control Solenoid Valve Assembly Connector B-111

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12. STEP 12. Check the harness for an open or short circuit to ground between PCM connector B-20 (terminals 54, 56 and 53) and A/T control solenoid valve assembly connector B-111 (terminals 7, 6 and 8). 

    Q: Are the harness wires in good condition? 

    1. YES:  Go to Step 13.
    2. NO:  Repair or replace the harness wire.
       Fig 20: Locating PCM Connector B-20

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       Fig 21: Locating A/T Control Solenoid Valve Assembly Connector B-111

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13. STEP 13. Check the harness for an open or short circuit to ground between A/T control solenoid valve assembly connector B-111 (terminals 7, 6, 8, and 10) and solenoid valve connectors B-111-4, B-111-5 and B-111-6. 

    Q: Is the harness wire in good condition? 

    1. YES:  Replace the PCM. When the PCM is replaced, register the encrypted code. Refer to ENCRYPTED CODE REGISTRATION CRITERIA TABLE .
    2. NO:  Replace the harness wire.
       Fig 22: Locating A/T Control Solenoid Valve Assembly Connector B-111

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       Fig 23: Locating Solenoid Valve Connectors B-111-4, B-111-5 And B-111-6

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