ASE4 OBD II and Scan Tool Diagnostics 2

Question 1

What type of information does OBD II Mode $06 provide to a technician?

Accepted Answer

On-board monitoring test results showing actual values versus pass/fail thresholds

Answer

A list of all current and pending DTCs with descriptions

Answer

Live PID data stream from all continuously monitored sensors

Answer

Freeze frame data from the most recently stored fault code

Question 2

A 'pending' DTC stored in Mode $07 means:

Accepted Answer

A fault was detected on one trip but has not yet been confirmed on a second trip

Answer

The DTC is confirmed and the MIL has been illuminated

Answer

The DTC was previously cleared but the original fault is still causing problems

Answer

The fault is only detected under extreme hot or cold temperature conditions

Question 3

On a scan tool, OBD II Mode $01 PID $0C displays which parameter?

Accepted Answer

Engine RPM calculated from the crankshaft position sensor

Answer

Vehicle speed in mph

Answer

Engine coolant temperature in degrees Fahrenheit

Answer

Throttle position sensor voltage

Question 4

A short-term fuel trim (STFT) reading of +15% indicates the ECM is:

Accepted Answer

Adding fuel to compensate for a lean condition detected by the O2 sensor

Answer

Reducing fuel delivery because the engine is running rich

Answer

Disabling one fuel injector to balance the air/fuel mixture

Answer

Advancing ignition timing to improve combustion efficiency

Question 5

What is the primary function of long-term fuel trim (LTFT) stored in the ECM?

Accepted Answer

To store learned baseline fuel corrections that persist across ignition cycles

Answer

To provide immediate fuel delivery corrections based on real-time O2 sensor feedback

Answer

To monitor catalytic converter oxygen storage capacity over time

Answer

To control EGR valve duty cycle during warm-up enrichment

Question 6

If both STFT and LTFT are consistently at -15% across all load conditions, the most likely cause is:

Accepted Answer

Excessive fuel delivery from high fuel pressure or leaking injectors

Answer

A large vacuum leak causing excessive unmetered air entry

Answer

A faulty upstream O2 sensor stuck in lean indication

Answer

An EGR valve stuck in the closed position

Question 7

Which pin of the OBD II DLC (Data Link Connector) provides unswitched battery voltage to power the scan tool?

Accepted Answer

Pin 16

Answer

Pin 2

Answer

Pin 4

Answer

Pin 14