Exam 31: Fuel Injection Diagnosis and Service

____________________ and hold injector circuits use two driver circuits to control injector action.

If the IAC counts are below 16 on a fully warmed up engine, there may be a problem with a(n)______.

Technician A uses a low-impedance test light to check for an injector pulse. Technician B uses a noid light to check the injector pulse. Who is correct?

The O₂ sensor should toggle between rich and lean ____________________ to ____________________ times in a ten-second period.

Technician A says the IAC counts should change when the A/C compressor is turned on and off. Technician B says if the scan tester indicates zero IAC counts, there may be an open circuit between the PCM and the IAC motor. Who is correct?

Describe a speed density system.

Technician A says higher than normal idle speed may be caused by an air-conditioning switch that is always closed. Technician B says higher than normal idle speed may be caused by a defective engine coolant temperature sensor. Who is correct?

Which of the following components can cause excessively high pressure in a returnless fuel delivery system?

Idle learn procedures for ETC (throttle-by-wire)-equipped vehicles are being discussed. Technician A says the learn or relearn procedure should be completed anytime the PCM has been replaced or updated, or after the throttle body has been cleaned or replaced. Technician B says the system does not need to relearn if the battery has been disconnected. The system will automatically go through the procedure when the engine is restarted.Who is correct?

An injector balance test requires an injector pulse tester and a ______..

What is the difference in signal output between an oxygen sensor and an A/F (air/fuel)ratio sensor?

Technician A checks GDI (gasoline direct injectors)injectors with a pulse tester . Technician B test GDI injectors with an ohmmeter. Who is correct?

Technician A says if a lean condition caused by a vacuum leak, restricted injectors, dirty MAF, clogged fuel filter, or bad fuel pump exists, the LTFT will have a negative number. Technician B says when the O2 sensor has a rich signal, the STFT goes lean to adjust the air/fuel ratio. Who is correct?

IAC motor damage may result if throttle body cleaner is allowed to enter the motor.

A vehicle with excessively high fuel pressure is being diagnosed. Technician A says the problem could be a restricted fuel return line. Technician B says the problem could be a shorted (closed)fuel pump relay. Who is correct?

Technician A says a small leak in the air duct between the MAF and the throttle body will not cause a driveability problem. Technician B says a small intake manifold leak in a speed density system will not cause a driveability problem. Who is correct?

When looking at an O₂S  pattern on a lab scope, what should you be looking for?

The engine must be at normal operating temperature before the ECT sensor is tested.

Technician A says a rich air/fuel ratio may be caused by low fuel pump pressure. Technician B says a rich air/fuel ratio may be caused by a defective engine coolant temperature sensor. Who is correct?

Which of the following should NOT be used to lubricate injector O-rings?