Diagnosis and Checking Procedure Using Instruments

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) Ok

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) Ok
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 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.