DESCRIPTION
Before beginning it is important to have all available information on the system to be tested. Also, get a thorough understanding of system operation. Then you will be able to use the appropriate equipment and follow the correct test procedure.
NOTE:
Refer to GI-36, "How to Check Terminal" to probe or check terminal.
Testing for “opens” in the circuit
Before you begin to diagnose and test the system, you should rough sketch a schematic of the system. This will help you to logically walk through the diagnosis process. Drawing the sketch will also reinforce your working knowledge of the system.
Before you begin to diagnose and test the system, you should rough sketch a schematic of the system. This will help you to logically walk through the diagnosis process. Drawing the sketch will also reinforce your working knowledge of the system.
Continuity Check Method
The continuity check is used to find an open in the circuit. The digital multimeter (DMM) set on the resistance function will indicate an open circuit as over limit (no beep tone or no ohms symbol). Make sure to always start with the DMM at the highest resistance level.
To help in understanding the diagnosis of open circuits, please refer to the previous schematic.
Any circuit can be diagnosed using the approach in the previous example.
Voltage Check Method
To help in understanding the diagnosis of open circuits please refer to the previous schematic.
In any powered circuit, an open can be found by methodically checking the system for the presence of voltage.
This is done by switching the DMM to the voltage function.
voltage; open is further down the circuit than SW1.
no voltage; open is between fuse block and SW1 (point A).
voltage; open is further down the circuit than the relay.
no voltage; open is between SW1 and relay (point B).
voltage; open is further down the circuit than the solenoid.
no voltage; open is between relay and solenoid (point C).
Any powered circuit can be diagnosed using the approach in the previous example.
Testing for “shorts” in the circuit
To simplify the discussion of shorts in the system, please refer to the following schematic.
Resistance Check Method
continuity; short is between fuse terminal and SW1 (point A).
no continuity; short is further down the circuit than SW1.
Then, check for continuity.
continuity; short is between SW1 and the relay (point B).
no continuity; short is further down the circuit than the relay.
continuity; short is between relay and solenoid (point C).
no continuity; check solenoid, retrace steps.
Voltage Check Method
voltage; short is between fuse block and SW1 (point A).
no voltage; short is further down the circuit than SW1
voltage; short is between SW1 and the relay (point B).
no voltage; short is further down the circuit than the relay.
voltage; short is down the circuit of the relay or between the relay and the disconnected solenoid (point C).
no voltage; retrace steps and check power to fuse block.
Ground inspection
Even when the ground connection looks clean, there can be a thin film of rust on the surface.
Voltage drop tests
Measuring Voltage Drop — Accumulated Method
Note in the illustration that there is an excessive 4.1 volt drop between the battery and the bulb.
Measuring Voltage Drop — Step-by-Step
Control unit circuit test
System Description
When the switch is ON, the control unit lights up the lamp.
CASE 1
The voltage value is based on the body ground.
*: If high resistance exists in the switch side circuit (caused by a single strand), terminal 1 does not detect battery voltage. Control unit does not detect the switch is ON even if the switch does not turn ON. Therefore, the control unit does not supply power to light up the lamp.
CASE 2
The voltage value is based on the body ground.
*: If high resistance exists in the switch side circuit (caused by a single strand), terminal 2 does not detect approx. 0V. Control unit does not detect the switch is ON even if the switch does not turn ON. Therefore, the control unit does not control ground to light up the lamp.
Basic inspection
Inspection and adjustment
Additional service when replacing control unit (bcm)
ADDITIONAL SERVICE WHEN REPLACING CONTROL UNIT (BCM) : Description
Before replacement
When replacing bcm, save or print current vehicle specification with consult
configuration before replacement.
Note:
If “B ...
Precaution
Precaution for supplemental restraint system (srs) "air bag" and "seat
belt pre-tensioner"
The supplemental restraint system such as “air bag” and “seat belt pre-tensioner”,
used along
with a front seat belt, helps to reduce the risk or severity of injur ...
Rear window defogger and door mirror defoggers do not operate
Diagnosis procedure
Regarding Wiring Diagram information, refer to DEF-20, "Wiring Diagram".
1. Check rear window defogger switch
Check rear window defogger switch.
Refer to def-30, "component function check".
Is the inspection result normal?
Yes >> go to 2.
No ...