Past Error - Open Circuit -

Review CAN communication signal chart based on information received from the interview with the customer and on past error information from DTC check and bus check.

1. DTC check: Inspect the control units indicating "U1000" or "U1001" on DTC check.
   Fig 1: [DTC Check Sheet]

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2. Bus check (with PAST): Check the bus check (with PAST) of units indicating "U1000" or "U1001" on DTC check. Draw a line on the diagnosis sheet to indicate the possible error circuit.
   NOTE: For the details of each indication on bus check, refer to [BUS CHECK ].
   1. Reception item of "ECM": "VDC/TCS/ABS", "3" is indicated in the "PAST". This means ECM could not receive the signal from ABS in the past. Draw a line between ECM and ABS (line 2-a in the figure below).
   2. Reception item of "M&A": "VDC/TCS/ABS", "3" is indicated in the "PAST". This means M&A could not receive the signal from ABS in the past. Draw a line between M&A and ABS (line 2-b in the figure below).
   3. Reception item of "TCM": "VDC/TCS/ABS", "3" is indicated in the "PAST". This means TCM could not receive the signal from ABS in the past. Draw a line between TCM and ABS (line 2-c in the figure below).
      Fig 2: CAN Communication Diagram (ECM And ABS)

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3. Bus check (without PAST): Check the bus check (without PAST) of units indicating "U1000" or "U1001" on DTC check. Draw a line on the diagnosis sheet to indicate the possible error circuit.
   NOTE:

   • While an error occurred in the past according to DTC check, it is unclear which signal is not received. Assume that errors were detected from all reception items.
   • Draw a single line among the unit and all reception items. (Work flow differs from Bus check (with PAST).)
   1. Reception item of "EPS": Assume that the unit could not receive the signals from ECM, ABS, and M&A. Draw a line among EPS, ECM, ABS, and M&A (line 3-a in the figure below).
   2. Reception item of "ABS": Assume that the unit could not receive the signal from ECM. Draw a line between ABS and ECM (line 3-b in the figure below).
      Fig 3: CAN Communication Diagram (ABS And ECM)

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4. Search for the possible cause using CAN communication signal chart using information from the interview with the customer.
   NOTE: For the details of CAN communication signal, refer to [CAN COMMUNICATION SIGNAL CHART ].
   1. ABS warning lamp turned ON and speedometer did not move: This means that "ABS warning lamp signal" and "Vehicle speed signal" could not communicate between M&A and ABS (4-a in the figure below).
   2. The tachometer moved normally: This means that "Engine speed signal" could communicate normally between ECM and M&A (4-b in the figure below).
      Fig 4: CAN Communication Signal Chart

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5. Fill out the diagnosis sheet based on information from step 4.
   1. The ABS warning lamp turned ON and speedometer did not move: Assume that a possible cause is no communication between M&A and ABS. Draw a line between M&A and ABS. (Line 5-a in the figure below).
   2. The tachometer moved normally: Put check marks between ECM and M&A. The circuit between ECM and M&A is functioning properly (check marks 5-b in the figure below).
      Fig 5: CAN Communication Diagram (ECM And M And A)

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6. The circuit which has the most amount of lines are the possible cause. Error is detected from ABS actuator and electric unit (control unit) branch line (shaded in the figure below).
   NOTE: For abbreviations, refer to [HOW TO USE THIS SECTION ].
7. Perform the inspection procedure for the possible cause. Refer to "MALFUNCTION AREA CHART ".
   Fig 6: CAN Communication Diagram (ABS Actuator And Electric Unit (Control Unit) Branch Line)

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