Exam 4: On Board Diagnostic Scanners and Digital Storage Oscilloscopes

While discussing OBD II systems: Technician A says if a misfire condition threatens engine or catalyst damage, the PCM flashes the MIL. Technician B says the PCM illuminates the MIL if a defect causes emission levels to exceed 1.5 times the emission standards for that model year. Who is correct?

What term is used to represent the highest point in one cycle of an AC voltage waveform?

An analog scope is less complicated and cheaper than a DSO (digital) scope.

Diagnostic scan tester operation varies depending on the make and model of the scan tool.

The PCM monitors exhaust temperatures to detect cylinder misfires.

While discussing the misfire monitor: Technician A says while detecting a Type B misfire, the monitor checks cylinder misfiring over a 1,000 rpm period. Technician B says while detecting a Type A misfire, the monitor checks cylinder misfiring over a 50 rpm period. Who is correct?

What are the advantages of the high-end OBD II handheld scan tools?

The DSO sampling time is at least 20 times faster than other automotive testers.

Technician A says all computer system problems can be solved by using a scan tool. Technician B says many computer-controlled components can be tested with an ohmmeter or voltmeter. Who is correct?

On a DSO screen, what value is displayed vertically?

What type of data is stored while a DTC is being set?

What features are included in an enhanced OBD II diagnostic scan tool and what do they allow the technician access to?

A technician is viewing a scan tool data stream to diagnose an OBD II system. The downstream HO₂S has the same voltage switching rate as the upstream HO₂S. Technician A says the air/fuel ratio is too rich. Technician B says the catalytic converter may be defective. Who is correct?

By referring to STFT and LTFT values, the technician can determine how the PCM is reacting to current engine operating conditions.

What was the major difference in connecting an OBD II and a pre-OBD II scan tool?

While discussing digital storage oscilloscopes: Technician A says the DSO shows the signals as they occur. Technician B says the DSO reads signals, stores them, and then displays them. Who is correct?

On an OBD II emission control system, both pre-catalyst and post-catalyst oxygen sensors are used.

An OBD II scan tool generally offers greater control and more in-depth service information than was available to the service technician with earlier-generation systems and tools.

What is the basic function of all scan tools?

What selection tells the DSO when to begin displaying a waveform?