HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE POINTS


CONTENTS OF TROUBLESHOOTING


caution During diagnosis, a diagnosis code associated with other system may be set when the ignition switch is turned on with connector(s) disconnected. On completion, confirm all systems for diagnosis code(s). If diagnosis code(s) are set, erase them all.
Troubleshooting of electronic control systems for which the M.U.T.-III can be used follows the basic outline described below. Even in systems for which the M.U.T.-III cannot be used, some of these systems still follow this outline.

1. STANDARD FLOW OF DIAGNOSIS TROUBLESHOOTING


Troubleshooting sections are based on the diagnostic flow as below. If the diagnostic flow is different from that given below, or if additional explanation is required, the details of such differences or additions will also be listed.
Diagnosis method


2. SYSTEM OPERATION AND SYMPTOM VERIFICATION TESTS


If verification of the symptom(s) is difficult, procedures for checking operation and verifying symptoms are shown.

3. DIAGNOSIS FUNCTION


Details which are different from those in the "Diagnosis Function " section are described.

4. DIAGNOSIS CODE CHART


Diagnosis codes and diagnostic items are shown.

5. DIAGNOSIS CODE PROCEDURES


Indicates the inspection procedures corresponding to each diagnosis code (Refer to How to Use Inspection Procedures ).

6. TROUBLE SYMPTOM CHART


If there are trouble symptoms even though the M.U.T.-III does not find any diagnosis codes, Inspection procedures for each trouble symptom will be found by means of this chart.

7. SYMPTOM PROCEDURES


Indicates the inspection procedures corresponding to each symptoms classified in the Symptom Chart (Refer to How to Use Inspection Procedures ).

8. SERVICE DATA REFERENCE TABLE


Inspection items and normal judgment values have been provided in this chart as reference information.

9. ACTUATOR TEST TABLE


The Actuator Test item numbers, inspection items, and judgment values have been provided in this chart as reference information.

10. CHECK AT ECU TERMINALS


Terminal numbers for the ECU connectors, inspection items, and judgment values have been provided in this chart as reference information.

11. INSPECTION PROCEDURE BY USING AN OSCILLOSCOPE


When there are inspection procedures using an oscilloscope, these are described here.

DIAGNOSIS FUNCTION


1. HOW TO READ DIAGNOSIS CODE


caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.

Connect the M.U.T.-III to the 16-pin diagnosis connector, and read the diagnosis code.
note For details on how to use the M.U.T.-III, refer to the "M.U.T.-III operation manual."
1.Ensure that the ignition switch is at the "LOCK" (OFF).
2.Start up the personal computer.
3.Connect M.U.T.-III USB cable MB991827 to special tool Vehicle Communication Interface (V.C.I.) MB991824 and the personal computer.
4.Connect M.U.T.-III main harness A MB991910 to the V.C.I.
5.Connect the M.U.T.-III main harness A to the diagnosis connector.
6.Turn the V.C.I. power switch to the "ON" position.
note When the V.C.I. is energized, the V.C.I. indicator lamp will be illuminated in a green colour.
7.Start the M.U.T.-III system on the personal computer and turn the ignition switch to the "ON" position.
8.Read the diagnosis code.
9.Disconnecting the M.U.T.-III is the reverse of the connecting sequence, making sure that the ignition switch is at the "LOCK" (OFF).

2. ERASING DIAGNOSIS CODE
caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.

Connect the M.U.T.-III to the diagnosis connector, and erase the diagnosis code. The procedure is the same as "How to Read Diagnosis Code ."

3. INPUT SIGNAL CHECK (WHEN USING THE M.U.T.-III) <SWS>
caution Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.

1.Connect the M.U.T.-III to the diagnosis connector, and erase the diagnosis code.
2.If the M.U.T.-III buzzer sounds once when each switch is operated (ON/OFF), the input signal for that switch circuit system is normal.

3. INPUT SIGNAL CHECK (WHEN USING A VOLTMETER) <SWS>

1.Use the special tool diagnosis code check harness (MB991529) to connect the ETACS terminal (terminal 9) and the earth terminals (terminals 4 and 5) of the diagnosis connector to the voltage meter.
2.If the needle of the voltage meter flickers once when each switch is operated (ON/OFF), the input signal for that switch circuit system is normal.

HOW TO USE THE INSPECTION PROCEDURES


The causes of many of the problems occurring in electric circuitry are generally the connectors, components, the ECU, the wiring harnesses between connectors, in that order. These inspection procedures follow this order. They first try to discover a problem with a connector or a defective component.



CURRENT TROUBLE


Indicates that the trouble is currently present. Carry out troubleshooting as described in the applicable inspection procedure.

PAST TROUBLE


Indicates that the status is "Stored" and the trouble is historic. Since the trouble may still be present, set the vehicle to the diagnosis code detection condition and check that the status changes to "Active". If the status does not change from "Stored", observe the applicable inspection procedure with particular emphasis on connector(s) and wiring harness.

HARNESS CHECK


Check for an open or short circuit in the harness between the terminals which were faulty according to the connector measurements. Carry out this inspection while referring to the Electrical Wiring Manual. Here, "Check the wiring harness between the power supply and terminal xx" also includes checking for blown fuse. For inspection service points when there is a blown fuse, refer to "Inspection Service Points for a Blown Fuse ."

MEASURES TO TAKE AFTER REPLACING THE ECU


If the trouble symptoms have not disappeared even after replacing the ECU, repeat the inspection procedure from the beginning.

CONNECTOR MEASUREMENT SERVICE POINTS
caution During diagnosis, a diagnosis code associated with other system may be set when the ignition switch is turned on with connector(s) disconnected. On completion, confirm all systems for diagnosis code(s). If diagnosis code(s) are set, erase them all.
Turn the ignition switch to the "LOCK" (OFF) position when connecting and disconnecting the connectors. Turn the ignition switch to "ON" when measuring, unless there are instructions to the contrary.

IF INSPECTING WITH THE CONNECTOR CONNECTED <WATERPROOF CONNECTORS>
caution Never insert a test probe from the harness side, as this will reduce the waterproof performance and result in corrosion.

Use the special tools such as test harness, harness connector or check harness.

IF INSPECTING WITH THE CONNECTOR CONNECTED <ORDINARY (NON-WATERPROOF) CONNECTORS>

Inspect by inserting a test probe from the harness side. If the connector is too small to insert a test probe (e.g. control unit connector), do not insert it forcibly. Use special tool MB992006 (extra fine probe).

IF INSPECTING WITH THE CONNECTOR DISCONNECTED <WHEN INSPECTING A FEMALE PIN>
caution
  • Use the special tool Check Harness (MB991219). If the test bar is inserted forcibly, it will cause a poor contact.
  • If the connector is disconnected, a diagnosis code may be stored for the system to be checked or other systems.

Use the Check Harness (MB991219) of the special tool Harness Set (MB991223).

IF INSPECTING WITH THE CONNECTOR DISCONNECTED <WHEN INSPECTING A MALE PIN>
caution
  • Be careful not to short the connector pins with the test bars. To do so may damage the circuits inside the ECU.
  • If the connector is disconnected, a diagnosis code may be stored for the system to be checked or other systems.

Touch the pin directly with the test bar.

CONNECTOR INSPECTION SERVICE POINTS


VISUAL INSPECTION


  • Connector is disconnected or improperly connected
  • Connector pins are pulled out
  • Due to harness tension at terminal section
  • Low contact pressure between male and female terminals
  • Low connection pressure due to rusted terminals or foreign matter lodged in terminals

CONNECTOR PIN INSPECTION

If the connector pin stopper is damaged, the terminal connections (male and female pins) will not be perfect even if the connector body is connected, and the pins may pull out of the reverse side of the connector. Therefore, gently pull the harnesses one by one to make sure that no pins pull out of the connector.

CONNECTOR ENGAGEMENT INSPECTION

Use special tool inspection harness (MB991219) (connector pin connection pressure inspection harness of the inspection harness set) to inspect the engagement of the male pins and female pins. (Pin drawing force: 1 N or more)

INSPECTION SERVICE POINTS FOR A BLOWN FUSE
caution A diagnosis code may be stored due to a blown fuse.

Remove the blown fuse and measure the resistance between the load side of the blown fuse and the earth. Close the switches of all circuits which are connected to this fuse. If the resistance is almost 0 Ω at this time, there is a short somewhere between these switches and the load. If the resistance is not 0 Ω, there is no short at the present time, but a momentary short has probably caused the fuse to blow.
The main causes of a short circuit are the following.

  • Harness being clamped by the vehicle body
  • Damage to the outer casing of the harness due to wear or heat
  • Water getting into the connector or circuitry
  • Human error (mistakenly shorting a circuit, etc.)

HOW TO COPE WITH INTERMITTENT MALFUNCTIONS

Intermittent malfunctions often occur under certain conditions, and if these conditions can be ascertained, determining the cause becomes simple. In order to ascertain the conditions under which an intermittent malfunction occurs, first ask the customer for details about the driving conditions, weather conditions, frequency of occurrence and trouble symptoms, and then try to recreate the trouble symptoms. Next, ascertain whether the reason why the trouble symptom occurred under these conditions is due to vibration, temperature or some other factor. If vibration is thought to be the cause, carry out the following checks with the connectors and components to confirm whether the trouble symptom occurs. The objects to be checked are connectors and components which are indicated by inspection procedures or given as probable causes (which generates diagnosis codes or trouble symptoms).

  • Gently shake the connector up, down and to the left and right.
  • Gently shake the wiring harness up, down and to the left and right.
  • Gently rock each sensor and relay, etc. by hand.
  • Gently shake the wiring harness at suspensions and other moving parts.
note If determining the cause is difficult, the drive recorder function of the M.U.T.-III can also be used. (For details on how to use the M.U.T.-III, refer to the "M.U.T.-III operation manual).

HOW TO TREAT PAST TROUBLE


Since the trouble may still be present even the status is "Stored", set the vehicle to the diagnosis code detection condition and check that the status changes to "Active". If the status does not change from "Stored", carry out the following procedure.
1.Establish from the customer whether a fuse or connector has been replaced or disconnected.
2.If yes, erase the diagnosis code, and then check that no diagnostic code is reset. If no diagnosis code is reset, the diagnosis is complete.
3.If no, follow the applicable Diagnostic Trouble Code Chart. Then check the wiring harness and connector, and refer to "How to Cope with Intermittent Malfunction ."