Tips on Diagnostic Charts and Basic Inspection Procedures

SYMBOLS

Circuit Tester / Voltage Measurement.

Circuit Tester / Resistance Measurement.

The arrow indicates that insertion of the probe or numbering of the connector pins is made from the side.

Oscilloscope.

Oscilloscope Positive Probe.

Oscilloscope Earth Head.

WARNINGS, CAUTIONS, NOTES

WARNING: Indicates the item which must be observed precisely during performance of maintenance services in order to avoid injury to the mechanics and other persons.

CAUTION: Indicates that item which must be followed precisely during performance of maintenance services so as to avoid damage and breakage to the vehicle and its parts and components.

NOTE: Indicates the hints, knacks, etc. which make the maintenance job easier.

BASIC CHECKS
DISCONNECTING CONNECTORS

Always hold the connector itself.

CAUTION: Don't pull the harness.

Insert a connector by pushing it all the way in. If the connector is equipped with a locking device, push it in until a clicking sound is heard.

To disconnect a locking connector, first re-lease the lock, then pull the connector off. Unlock by pulling the locking tab.

Unlock by pushing the locking tab.

INSERTING A PROBE

- Generally, probes are inserted into connectors from the rear.
- Connectors equipped with shock protectors must be checked with a mini probe (thin), or it will be necessary to remove the shock protector.
- When removing the shock protector take care not to deform it; this also applies to waterproof connectors, which can not be tested from the wire side.
- When the connector has a back plate, remove the plate after removing the projection of the plate first. (Be careful not to use excessive force, since the terminals might break off).

CHECKING FOR POOR CONTACT ON PLUG-IN CONNECTORS
Most intermittent problems are caused by poor contact of plug-in connectors. Poor contact is frequently caused by corroded terminals, dirt, foreign substances, weak contact points between male and female connectors, etc. To help prevent the replacement of good component parts, sufficiently check the following points.
- Quite often a plug with poor contact will work perfectly again after it has been pulled off and reconnected.

- Disconnect the two connector halves.
- Check the connector pins for signs of corrosion or foreign material.
- Check the connector for loose and damaged terminals, and make sure they are set correctly in the connector.

NOTE: When the harness is pulled lightly, the terminals should not come out.

- Insert the male pin of the connector into the female pin, then pull it out.

NOTE: If one of the pins pulls out easily, it is a likely source of a malfunction.

- Lightly shake the connector and the harness, and check for sudden changes in voltage or resistance. If harness and connector checks do not reveal any defect, it can be assumed that an intermittent contact in a connector is the source of trouble.

DIAGNOSIS AND CHECKING PROCEDURE USING INSTRUMENTS

USING A CIRCUIT TESTER
- Voltage Check (range set to DC Volts)
Connect the positive probe to the terminal to be tested, and the negative probe to body ground (or the ground terminal of the Engine Control Module (ECM)).

- Checking the Connection (range set to "Ohm")
Measure the resistance and check for open or shorted wire in the harness or the connector.

NOTE: This check must be carried out with both connectors disconnected. (This avoids by-passing the connection through other circuits).

1. Check for open circuit (range: Ohm x 1K).
Measure the resistance between the respective pins in both connectors.

Specified Resistance:
1 M Ohm, or more (No continuity) Open circuit.
10 Ohms, or less (Continuity) O.K.

2. Check for correct insulation value (range: Ohm x 1K).
Measure the resistance between the pins in both connectors, as well as between the suspected pin and the body (body short).

Specified resistance:
1 M Ohm, or more (No continuity) O.K.
10 Ohms, or less (Continuity) Short circuit.

- Resistance Measurement (range set to Ohm)
Measuring the internal resistance of sensors, Solenoid Valves etc. to check the operating condition of components.

NOTE: Select the appropriate range for measuring the internal resistance, or the measurement will result in an incorrect reading. Before changing the measurement range the gauge must be reset to zero.

USING A SUBARU SELECT MONITOR
With this testing procedure the defective component can be determined by directly monitoring input/output signals of the Engine Control Module (ECM) or the Trouble Codes.

- Features
A variety of data can be checked without movements from the drivers seat, passenger's seat or from outside the vehicle. This unit allows the identification of the type of malfunction; for example, whether the cause is an open or shorted wire in the input/output signal line, or whether the breakdown of a component is caused by a lack of maintenance.

- Diagnosis
Refer to the reference values for input/output and control data to determine whether the malfunction is caused by a worn out component, an open wire, a short etc. Perform diagnostics procedure as described in "Check based on trouble codes" by monitoring the trouble codes.

NOTE: It will be easier to determine a malfunction if the vehicle data for normal conditions are available for comparison.

1. Connect Select Monitor.
a. Connect Select Monitor to Data Link Connector located under instrument panel (on driver's side).
b. Insert cartridge into Select Monitor.

c. Turn Ignition Switch and Select Monitor Switch "ON".
d. After display is shown, press slash "[/]" key.
e. After A/T mode is displayed, press function "[O]". (Display returns to A/T mode when slash "[/]" is pressed during on-board diagnostic operation.)

2. Read Trouble Code shown on display.
a. Connect Select Monitor.
b. Designate mode using function key. Press [F] [B] [0] [ENT] in that order.
c. Ensure that trouble code(s) are shown.

3. Previous Trouble Code reading.
a. Connect Select Monitor.
b. Designate mode using function key. Press [F] [B] [1] [ENT] in that order.
c. Ensure displayed trouble code(s).

USING AN OSCILLOSCOPE
A malfunction can be determined by displaying the waveforms of input/output signals on the Oscilloscope.

- Diagnosis
A simple comparison of the waveforms may lead to an incorrect diagnosis. To exactly determine the sources of the malfunction it will be necessary to determine them under consideration about information other than waveforms.

- Applying Input/Output Signals
Connect the probe directly with the terminal of the signal.