Detect The Root Cause

Identify the root cause using the created diagnosis sheet.

Identifying the root cause

• Draw a line on the diagnosis sheet to indicate the possible cause. Narrow the search.
  NOTE:

  • Color-code when drawing lines.
  • Do not draw a line onto a existing line.
• Drawing a line is not necessary if the circuit is shorted. Refer to "Present Error - Short Circuit -", "Past Error - Short Circuit -".

Refer to the following for details of the trouble diagnosis procedure.

• "Present Error - Open Circuit -"
• "Present Error - Short Circuit -"
• "Past Error - Open Circuit -"
• "Past Error - Short Circuit -"

Present Error - Open Circuit -

Identify the error circuit using information from the "CAN DIAG SUPPORT MNTR"

1. Check the items indicated in "ALL DTC". Draw a line on the diagnosis sheet to indicate the error circuit.
   NOTE: CAN communication line has no error if units other than Diag on CAN units are not indicated. An error may be on the power supply of the control unit, DDL1 line or DDL2 line.
   1. "TCM" which is Diag on CAN unit, is not indicated on "ALL DTC." This indicates that DLC is not receiving a signal from TCM. Draw a line to indicate an error between DLC and TCM (line 1-a in the figure below).
      NOTE:

      • Diag on CAN units are not indicated on the "ALL DTC" when the CAN line between Diag on CAN unit and the data link connector is open.
      • For a description of Diag on CAN, refer to "DESCRIPTION ".
      Fig 1: Example Of Detect Root Cause

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2. CAN DIAG SUPPORT MNTR: Check each item on "CAN DIAG SUPPORT MNTR". Draw a line on the diagnosis sheet to indicate the error circuit. 
   1. Reception item of "ENGINE": On "TCM", "UNKWN" is indicated. This means ECM cannot receive the signal from TCM. Draw a line to indicate an error between ECM and TCM (line 2-a in the figure below).
      NOTE: If "UNKWN" is indicated on "TRANSMIT DIAG", then the control unit cannot transmit CAN communication signal to each unit. Draw a line between the control unit and the splice.
   2. Reception item of "ADAPTIVE LIGHT": On "TCM", "UNKWN" is indicated. This means AFS cannot receive the signal from TCM. Draw a line to indicate an error between AFS and TCM (line 2-b in the figure below).
   3. Reception item of "MULTI AV": "UNKWN" is not indicated. This indicates normal communication between AV and its receiving units. Do not draw any line.
      Fig 2: Example Of CAN DIAG Support MNTR

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   4. Reception item of "BCM": On "TCM", "UNKWN" is indicated. This means BCM cannot receive the signal from TCM. Draw a line to indicate an error between BCM and TCM (line 2-d in the figure below).
   5. Reception item of "EPS" and "INTELLIGENT KEY": "UNKWN" is not indicated. This indicates normal communication between EPS and I-KEY and their receiving units. Do not draw any line.
      NOTE: On CAN DIAG SUPPORT MNTR (without PAST), "UNKWN" is indicated even though the item is not used in the trouble diagnosis. For the details of each item on CAN diagnostic support monitor, refer to "CAN DIAGNOSTIC SUPPORT MONITOR ".
      Fig 3: Example Of On CAN DIAG Support MNTR (Without Past)

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   6. Reception item of "METER/M&A": On "TCM", "UNKWN" is indicated. This means M&A cannot receive the signal from TCM. Draw a line to indicate an error between M&A and TCM (line 2-f in the figure below).
   7. Reception item of "AUTO DRIVE POS.": On "TCM", "UNKWN" is indicated. This means ADP cannot receive the signal from TCM. Draw a line to indicate an error between ADP and TCM (line 2-g in the figure below).
   8. Reception item of "ABS": "UNKWN" is not indicated. This indicates normal communication between ABS and its receiving units. Do not draw any line.
      Fig 4: Example Of Reception Item Of "ABS": "Unkwn"

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   9. Reception item of "IPDM E/R": "UNKWN" is not indicated. This indicates normal communication between IPDM-E and its receiving units. Do not draw any line.
3. Based on information received from "CAN DIAG SUPPORT MNTR", place a check mark on the known good CAN communication line between ECM and IPDM-E.
   1. Through the previous procedure, the circuit between ADP splice and TCM has the most amount of lines (shade 3-a in the figure below).
   2. Place a check mark on the known good lines to establish the error circuit.

   Reception item of "IPDM E/R": On "ECM", "OK" is indicated. IPDM-E communicates normally with ECM. Put a check mark on the normal circuit between ECM and IPDM-E (check mark 3-b in the figure below).

   Fig 5: Example Of Reception Item Of "IPDM E/R" On "ECM", "Ok"

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4. Through the above procedure, the error is detected in the TCM branch line (shaded in the figure below).
   NOTE: For abbreviations, refer to "ABBREVIATION LIST ".
5. Perform the inspection for the detected error circuit. For the inspection procedure, refer to "MALFUNCTION AREA CHART".
   Fig 6: Example Of Malfunction Area Chart

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Present Error - Short Circuit -

When the symptoms listed below exist, a short circuit of the CAN communication line is a possible cause.

Error symptom 

• Most the units connected to the CAN communication system go into fail-safe mode or are deactivated.

Inspection procedure 

• Refer to "MALFUNCTION AREA CHART".
  Fig 7: Example Of Malfunction Area Chart

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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 SELF-DIAG RESULTS and CAN DIAG SUPPORT MNTR.

1. SELF-DIAG RESULTS: Inspect the control units indicating "U1000" or "U1001" on SELF-DIAG RESULTS.
   Fig 8: Display - Self-DIAG Results

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2. CAN DIAG SUPPORT MNTR (with PAST): Check the CAN DIAG SUPPORT MNTR (with PAST) of units indicating "U1000" or "U1001" on SELF-DIAG RESULTS. Draw a line on the diagnosis sheet to indicate the possible error circuit. 
   NOTE: For the details of each indication on CAN DIAG SUPPORT MNTR, refer to "CAN DIAGNOSTIC SUPPORT MONITOR ".
   1. Reception item of "ENGINE": "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 "METER/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 "TRANSMISSION": "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 9: Example Of Reception Item Of "Transmission": "VDC/TCS/ABS", "3"

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3. CAN DIAG SUPPORT MNTR (without PAST): Check the CAN DIAG SUPPORT MNTR (without PAST) of units indicating "U1000" or "U1001" on SELF-DIAG RESULTS. Draw a line on the diagnosis sheet to indicate the possible error circuit. 
   NOTE:

   • While an error occurred in the past according to SELF-DIAG RESULTS, 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 CAN DIAG SUPPORT MNTR (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 10: Example Of Reception Item Of "ABS"

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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 11: Example Of 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 12: Example Of Circuit Between ECM And M&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 "ABBREVIATION LIST ".
7. Perform the inspection procedure for the possible cause. Refer to "MALFUNCTION AREA CHART".
   Fig 13: Example Of Malfunction Area Chart

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Past Error - Short Circuit -

When the symptoms listed below exist, a short circuit of the CAN communication line is a possible cause.

Fig 14: Example Of CAN Communication Line Short Circuit Symptoms

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