LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2017 >> Prius Prime Plus >> Repair and Diagnosis (Single Page) >> Restraints >> Restraints Control Systems >> Pre-Collision System - Diagnostic Codes & Circuit Tests >> Pre-Collision System >> DTC U1002: Lost Communication with Gateway Module [12/2018 - 07/2020] >> Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC U1002: Lost Communication with Gateway Module [12/2018 - 07/2020]: Procedure

  1. CHECK CAN BUS LINE (MALFUNCTION CONFIRMATION) 
    1. Turn the power switch off.
    2. Disconnect the cable from the negative (-) auxiliary battery terminal.
    3. Measure the resistance according to the value(s) in the table below.
      GTY718502Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Driving Support ECU Assembly)

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      I41-8 (CA1P) - I41-9 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal 54 to 69 Ω Below 54 Ω:
      Short circuit between bus lines
      70 Ω or more:
      Open circuit in a main bus line or driving support ECU assembly branch line
      I41-8 (CA1P) - I41-28 (GND) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Below 200 Ω:
      CANH ground short
      I41-9 (CA1N) - I41-28 (GND) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Below 200 Ω:
      CANH ground short
      I41-8 (CA1P) - I41-7 (B) Cable disconnected from negative (-) auxiliary battery terminal 6 kΩ or higher Below 6 kΩ:
      CANH +B short
      I41-9 (CA1N) - I41-7 (B) Cable disconnected from negative (-) auxiliary battery terminal 6 kΩ or higher Below 6 kΩ:
      CANH +B short

      Result

      Result Proceed to
      OK A
      NG (Open circuit in main line or Driving support ECU assembly branch line) B
      NG (Short circuit between main lines) C
      NG (Short to +B or ground) D

    Result: 

    B 

    See step  3

    Result: 

    C 

    See step  8

    Result: 

    D 

    See step  12

    Result: 

    A 

    See step  2

  2. CHECK FOR DTCs (PRE-COLLISION SYSTEM) 
    1. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [09/2016 - 07/2020]

      Body Electrical > Pre-Collision 2 > Clear DTCs 

    2. Perform the following procedure.

      HINT: 

      If the following procedure is not performed, the previously output DTC cannot be detected.

      1. Turn the power switch on (IG) and wait 2 seconds or more.
    3. Check for DTCs.

      Refer to DTC CHECK / CLEAR [09/2016 - 07/2020]

      Body Electrical > Pre-Collision 2 > Trouble Codes 

      Result

      Result Proceed to
      DTC U1002 is not output A
      DTC U1002 is output B

    Result: 

    A 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [09/2016 - 05/2019]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [05/2019 - 07/2020] 

    Result: 

    B 

    REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  COMPONENTS [09/2016 - 07/2020] 

  3. CHECK FOR OPEN IN CAN BUS BRANCH LINES (DRIVING SUPPORT ECU ASSEMBLY) 
    1. Disconnect the I41 driving support ECU assembly connector.
      GTY727760Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Driving Support ECU Assembly)
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      I41-8 (CA1P) - I41-9 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω

      HINT: 

      If the resistance is between 108 and 132 Ω, there may be an open in a CAN bus main line. If the value is 132 Ω or more, there may be an open in a CAN bus branch line between the No. 4 CAN junction connector and the driving support ECU or a connector may be disconnected.

    3. Connect the I41 driving support ECU assembly connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  7

    Result: 

    OK 

    See step  4

  4. CHECK FOR OPEN IN CAN BUS MAIN LINES (NO. 4 CAN JUNCTION CONNECTOR) 
    1. Disconnect the I77 No. 4 CAN junction connector.
      GTY704394Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 4 CAN Junction Connector)
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Connected to
      I77-11 (CANH) - I77-22 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω Forward Recognition Camera
      I77-9 (CA1P) - I77-20 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω Millimeter Wave Radar Sensor Assembly
    3. Connect the I77 No. 4 CAN junction connector.

      Result

      Result Proceed to
      OK A
      NG (Forward Recognition Camera Main Line) B
      NG (Millimeter Wave Radar Sensor Assembly Main Line) C

    Result: 

    A 

    REPLACE NO. 4 CAN JUNCTION CONNECTOR 

    Result: 

    C 

    See step  6

    Result: 

    B 

    See step  5

  5. CHECK FOR OPEN IN CAN BUS MAIN LINES (FORWARD RECOGNITION CAMERA) 
    1. Disconnect the O6 forward recognition camera connector.
      GTY736338Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Forward Recognition Camera)
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      O6-6 (CANH) - O6-12 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω
    3. Connect the O6 forward recognition camera connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FORWARD RECOGNITION CAMERA. Refer to  COMPONENTS [09/2016 - 07/2020] 

    Result: 

    NG 

    REPAIR OR REPLACE CAN BUS MAIN LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - FORWARD RECOGNITION CAMERA) 

  6. CHECK FOR OPEN IN CAN BUS MAIN LINES (MILLIMETER WAVE RADAR SENSOR ASSEMBLY) 
    1. Disconnect the A2 millimeter wave radar sensor assembly connector.
      GTY586191Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Millimeter Wave Radar Sensor Assembly)
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A2-5 (CA1P) - A2-6 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω
    3. Connect the A2 millimeter wave radar sensor assembly connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE MILLIMETER WAVE RADAR SENSOR ASSEMBLY. Refer to  COMPONENTS [09/2016 - 07/2020] 

    Result: 

    NG 

    REPAIR OR REPLACE CAN BUS MAIN LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - MILLIMETER WAVE RADAR SENSOR ASSEMBLY) 

  7. CHECK FOR OPEN IN CAN BUS BRANCH LINES (DRIVING SUPPORT ECU ASSEMBLY) 
    1. Disconnect the I41 driving support ECU assembly connector.
      GTY727760Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Driving Support ECU Assembly)
    2. Disconnect the I77 No. 4 CAN junction connector.
      GTY704395Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 4 CAN Junction Connector)
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      I77-10 (CA1P) - I41-8 (CA1P) Cable disconnected from negative (-) auxiliary battery terminal Below 1 Ω
      I77-21 (CA1N) - I41-9 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal Below 1 Ω
    4. Connect the I77 No. 4 CAN junction connector.
    5. Connect the I41 driving support ECU assembly connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE NO. 4 CAN JUNCTION CONNECTOR 

    Result: 

    NG 

    REPAIR OR REPLACE CAN BUS BRANCH WIRE (NO. 4 CAN JUNCTION CONNECTOR - DRIVING SUPPORT ECU ASSEMBLY) 

  8. CHECK FOR SHORT BETWEEN CAN BUS LINES (FORWARD RECOGNITION CAMERA) 
    1. Disconnect the O6 forward recognition camera connector.
      GTY736338Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Forward Recognition Camera)
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      O6-6 (CANH) - O6-12 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω
    3. Connect the O6 forward recognition camera connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FORWARD RECOGNITION CAMERA. Refer to  COMPONENTS [09/2016 - 07/2020] 

    Result: 

    NG 

    See step  9

  9. CHECK FOR SHORT BETWEEN CAN BUS LINES (NO. 4 CAN JUNCTION CONNECTOR) 
    1. Disconnect the I77 No. 4 CAN junction connector.
      GTY704392Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to No. 4 CAN junction connector)
      *b to Forward Recognition Camera
      *c to Millimeter Wave Radar Sensor Assembly
      *d to Driving Support ECU Assembly
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Connected to
      I77-11 (CANH) - I77-22 (CANL) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω Forward Recognition Camera
      I77-9 (CA1P) - I77-20 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω Millimeter Wave Radar Sensor Assembly
      I77-10 (CA1P) - I77-21 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Driving Support ECU Assembly
    3. Connect the I77 No. 4 CAN junction connector.

      Result

      Result Proceed to
      OK A
      NG (Forward Recognition Camera Main Line) B
      NG (Millimeter Wave Radar Sensor Assembly Main Line) C
      NG (Driving Support ECU Assembly Branch Line) D

    Result: 

    A 

    REPLACE NO. 4 CAN JUNCTION CONNECTOR 

    Result: 

    B 

    REPAIR OR REPLACE CAN BUS MAIN LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - FORWARD RECOGNITION CAMERA) 

    Result: 

    D 

    See step  11

    Result: 

    C 

    See step  10

  10. CHECK FOR SHORT BETWEEN CAN BUS LINES (MILLIMETER WAVE RADAR SENSOR ASSEMBLY) 
    1. Disconnect the A2 millimeter wave radar sensor assembly connector.
      GTY586191Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Millimeter Wave Radar Sensor Assembly)
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A2-5 (CA1P) - A2-6 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal 108 to 132 Ω
    3. Connect the A2 millimeter wave radar sensor assembly connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE MILLIMETER WAVE RADAR SENSOR ASSEMBLY. Refer to  COMPONENTS [09/2016 - 07/2020] 

    Result: 

    NG 

    REPAIR OR REPLACE CAN BUS MAIN LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - MILLIMETER WAVE RADAR SENSOR ASSEMBLY) 

  11. CHECK FOR SHORT BETWEEN CAN BUS LINES (DRIVING SUPPORT ECU ASSEMBLY) 
    1. Disconnect the I41 driving support ECU assembly connector.
      GTY727760Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Front view of wire harness connector
      (to Driving Support ECU Assembly)
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      I41-8 (CA1P) - I41-9 (CA1N) Cable disconnected from negative (-) auxiliary battery terminal 54 to 69 Ω
    3. Connect the I41 driving support ECU assembly connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  COMPONENTS [09/2016 - 07/2020] 

    Result: 

    NG 

    REPAIR OR REPLACE CAN BUS BRANCH LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - DRIVING SUPPORT ECU ASSEMBLY) 

  12. CHECK FOR SHORT IN CAN BUS LINE (FORWARD RECOGNITION CAMERA) 
    1. Disconnect the O6 forward recognition camera connector.
      GTY918232Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 DLC3 - -
      *a Front view of wire harness connector
      (to Forward Recognition Camera)      		 - -
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      O6-6 (CANH) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      O6-12 (CANL) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      O6-6 (CANH) - I96-16 (BAT) Cable disconnected from negative (-) auxiliary battery terminal 6 kΩ or higher
      O6-12 (CANL) - I96-16 (BAT) Cable disconnected from negative (-) auxiliary battery terminal 6 kΩ or higher
    3. Connect the O6 forward recognition camera connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FORWARD RECOGNITION CAMERA. Refer to  COMPONENTS [09/2016 - 07/2020] 

    Result: 

    NG 

    See step  13

  13. CHECK FOR SHORT IN CAN BUS LINE (NO. 4 CAN JUNCTION CONNECTOR) 
    1. Disconnect the I77 No. 4 CAN junction connector.
      GTY928909Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 DLC3 - -
      *a Front view of wire harness connector
      (to No. 4 CAN junction connector)      		 *b to Forward Recognition Camera
      *c to Millimeter Wave Radar Sensor Assembly *d to Driving Support ECU Assembly
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Connected to
      I77-11 (CANH) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Forward Recognition Camera
      I77-22 (CANL) - I96-4 (CG)
      I77-11 (CANH) - I96-16 (BAT) 6 kΩ or higher
      I77-22 (CANL) - I96-16 (BAT)
      I77-9 (CA1P) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Millimeter Wave Radar Sensor Assembly
      I77-20 (CA1N) - I96-4 (CG)
      I77-9 (CA1P) - I96-16 (BAT) 6 kΩ or higher
      I77-20 (CA1N) - I96-16 (BAT)
      I77-10 (CA1P) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher Driving Support ECU Assembly
      I77-21 (CA1N) - I96-4 (CG)
      I77-10 (CA1P) - I96-16 (BAT) 6 kΩ or higher
      I77-21 (CA1N) - I96-16 (BAT)
    3. Connect the I77 No. 4 CAN junction connector.

      Result

      Result Proceed to
      OK A
      NG (Forward Recognition Camera Main Line) B
      NG (Millimeter Wave Radar Sensor Assembly Main Line) C
      NG (Driving Support ECU Assembly Branch Line) D

    Result: 

    A 

    REPLACE NO. 4 CAN JUNCTION CONNECTOR 

    Result: 

    B 

    REPAIR OR REPLACE CAN BUS MAIN LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - FORWARD RECOGNITION CAMERA) 

    Result: 

    D 

    See step  15

    Result: 

    C 

    See step  14

  14. CHECK FOR SHORT IN CAN BUS LINE (MILLIMETER WAVE RADAR SENSOR ASSEMBLY) 
    1. Disconnect the A2 millimeter wave radar sensor assembly connector.
      GTY921942Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 DLC3 - -
      *a Front view of wire harness connector
      (to Millimeter Wave Radar Sensor Assembly)      		 - -
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A2-5 (CA1P) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      A2-6 (CA1N) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      A2-5 (CA1P) - I96-16 (BAT) Cable disconnected from negative (-) auxiliary battery terminal 6 kΩ or higher
      A2-6 (CA1N) - I96-16 (BAT) Cable disconnected from negative (-) auxiliary battery terminal 6 kΩ or higher
    3. Connect the A2 millimeter wave radar sensor assembly connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE MILLIMETER WAVE RADAR SENSOR ASSEMBLY. Refer to  COMPONENTS [09/2016 - 07/2020] 

    Result: 

    NG 

    REPAIR OR REPLACE CAN BUS MAIN LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - MILLIMETER WAVE RADAR SENSOR ASSEMBLY) 

  15. CHECK FOR SHORT IN CAN BUS LINE (DRIVING SUPPORT ECU ASSEMBLY) 
    1. Disconnect the I41 driving support ECU assembly connector.
      GTY840430Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *1 DLC3 - -
      *a Front view of wire harness connector
      (to Driving Support ECU Assembly)      		 - -
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      I41-8 (CA1P) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      I41-9 (CA1N) - I96-4 (CG) Cable disconnected from negative (-) auxiliary battery terminal 200 Ω or higher
      I41-8 (CA1P) - I96-16 (BAT) Cable disconnected from negative (-) auxiliary battery terminal 6 kΩ or higher
      I41-9 (CA1N) - I96-16 (BAT) Cable disconnected from negative (-) auxiliary battery terminal 6 kΩ or higher
    3. Connect the I41 driving support ECU assembly connector.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  COMPONENTS [09/2016 - 07/2020] 

    Result: 

    NG 

    REPAIR OR REPLACE CAN BUS BRANCH LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - DRIVING SUPPORT ECU ASSEMBLY) 

scientia non olet · About LEMON Manuals