Diagnostic Strategies

- The connector symbols show the pin arrangement as seen when looking at the terminals of the component.

- When the standard value when checking the voltage is recorded as B+, this is an abbreviation for battery positive voltage.





- When checking a waterproof connector with the circuit in a live state, be sure to use the special tool (test harness). Inserting the test probe from the harness side should never be done, as it will adversely affect waterproof performance, which may lead to corrosion.
Furthermore, the test harness is used for each setting, so the appropriate item for the connector should be selected.





- In addition, if there is no test harness for the appropriate connector, the test harness set (MB991348) which can be connected directly between the terminals can be used.

- When checking the terminal voltage, etc., with the connectors disconnected, do not insert the test probe if the check terminal has female pins.

Forcing the test probe into such a terminal can cause poor contact.





- When checking for a open circuit in a harness with both ends of the harness physically separated, use a jumper lead to ground one end and check continuity between the other end and the ground. This enables checking for a open circuit in the harness to be made. If there is no continuity, repair the harness.

However, when checking for a open circuit in the power supply line, check the continuity between both ends directly, without using a jumper lead to ground one end of the harness.





- When checking for a harness short-circuit, open one end of the harness and check for continuity between the other end and ground.

If there is continuity, the harness is short-circuited to ground, so repair the harness.

- As a rule, use an analog type ohmmeter (or circuit tester) to measure the continuity.





- If the harness is normal, but the voltage sent to the sensor is not normal, remove wire from harness and check voltage at engine control module pin. Before replacing engine control module, for improper voltage, verify power supply and grounds are correct. Replace engine control module and recheck.

- As a rule, use a digital type voltmeter (or circuit tester) to measure the voltage.

However, for checking the power transistor drive voltage, use an analog type voltmeter.