Question 1

The Motronic system is able to perform a "plausibility" test on the MAF sensor. What does this mean?

Accepted Answer

C

Question 2

Which statement about a turbocharged engine Motronic system is correct?

Accepted Answer

Both statements are correct because the Motronic system can use boost pressure reduction and spark retard as methods to control spark knock in turbocharged engines.

Question 3

Which sensor is commonly used on a Bosch Motronic system to allow the PCM to distinguish between engine misfire and an erratic crankshaft signal caused by rough road surfaces?

Accepted Answer

The chassis accelerometer is commonly used in Bosch Motronic systems to differentiate between engine misfire and erratic crankshaft signals caused by rough road surfaces. It measures the acceleration of the vehicle's chassis, helping the Powertrain Control Module (PCM) to accurately interpret vibrations and movements.

Question 4

Technician A says that European vehicles may have two data link connectors: an OBD II standardized DLC under the instrument panel and a manufacturer proprietary DLC designed for dealership scan tools. Technician B says that modern European vehicles will have a CAN data bus that will connect with the OBD II DLC. Who is correct?

Accepted Answer

Both technicians are correct. Technician A is correct in stating that European vehicles may have two types of data link connectors: one for OBD II under the dashboard and another proprietary one for dealership tools. Technician B is correct in saying that modern European vehicles use a CAN (Controller Area Network) data bus system, which interfaces with the OBD II DLC for diagnostics and communication.

Question 5

Which GDI engine charge mode is used for providing a rich air-fuel ratio when the vehicle is under moderate-to-heavy load?

Accepted Answer

The answer of Which GDI engine charge mode is used...

Question 6

Bosch pulsed multipoint injection systems are being discussed. Technician A says the injectors may be operated sequentially. Technician B says the injectors may be operated in clustered groups. Who is correct?

Accepted Answer

Bosch pulsed multipoint injection systems can operate injectors both sequentially and in clustered groups, making both Technician A and Technician B correct.

Question 7

What is the principal input used by an L-Jetronic system to determine how much fuel to inject?

Accepted Answer

The L-Jetronic system, developed by Bosch, primarily uses air flow as the principal input to determine the amount of fuel to inject into the engine. This system measures the volume of air entering the engine using an air flow meter, and then calculates the required amount of fuel to maintain the correct air-fuel ratio.

Question 8

Cranking mode is being discussed. Technician A says extra injector pulses may be used to richen the mixture. Technician B says an extra injector may be used to richen the mixture. Who is correct?

Accepted Answer

Both A and B are correct because extra injector pulses or an extra injector can be used to richen the mixture during cranking mode.

Question 9

What is the principal difference between the L-Jetronic and LH-Jetronic systems?

Accepted Answer

The principal difference between the L-Jetronic and LH-Jetronic fuel injection systems is the type of air flow sensor used. The L-Jetronic uses a flapper-type air flow meter, while the LH-Jetronic uses a hot wire air mass meter.

Question 10

Which of these statements about knock sensors is correct?

Accepted Answer

Knock sensors generate a voltage signal when they detect engine knocking or pinging, which is then used by the engine control unit to adjust the ignition timing.

Question 11

Which of these inputs is NOT used by the PCM to modify the read-only map for ignition timing?

Accepted Answer

The PCM (Powertrain Control Module) uses various inputs to adjust ignition timing for optimal engine performance and efficiency. Inputs such as intake air temperature, engine coolant temperature, and throttle position are directly used to modify the read-only map for ignition timing. However, air flow is not directly used for ignition timing adjustments; it is more closely related to fuel injection calculations.

Question 12

Why does the main power relay on a Bosch Motronic fuel injection system contain a diode?

Accepted Answer

The diode in the main power relay of a Bosch Motronic fuel injection system is designed to protect the Powertrain Control Module (PCM) against voltage surges and accidental polarity reversals. This ensures the PCM's safety and proper functioning by preventing potential damage from electrical issues.

Question 13

Which statement regarding air-fuel ratio is correct?

Accepted Answer

Both statements are correct. The ideal air-fuel ratio for complete combustion is known as stoichiometric, and lambda is a dimensionless number that describes the ratio of actual air-fuel mixture to the stoichiometric mixture.

Question 14

The injectors are being serviced on a Bosch fuel injection system. Technician A says the seals often leak and should be inspected carefully any time the injectors are removed. Technician B says petroleum jelly is generally regarded as the best O-ring installation lubricant. Who is correct?

Accepted Answer

Technician A is correct because seals in fuel injection systems, including those on Bosch systems, can indeed leak and should be inspected whenever injectors are removed to prevent fuel leaks and potential engine damage. Technician B is incorrect because petroleum jelly should not be used on O-rings in fuel systems as it can degrade the rubber. A lubricant compatible with the O-ring material and the fuel should be used instead.

Question 15

What is the primary advantage of using a cold start fuel injector?

Accepted Answer

The answer of What is the primary advantage of using...

Question 16

Motronic fuel systems are being discussed. Technician A says the fuel pump is directly controlled by the PCM. Technician B says some systems use a pulse damper to regulate fuel pressure. Who is correct?

Accepted Answer

The answer of Motronic fuel systems are being discussed. Technician...

Question 17

Early Motronic idle speed controls are being discussed. Technician A says an idle air bypass device is used to increase idle speed when the engine is cold. Technician B says the rotary idle control valve is used to control idle speed at any engine temperature. Who is correct?

Accepted Answer

Both technicians are correct. Technician A is correct in stating that an idle air bypass device is used to increase idle speed when the engine is cold, which helps the engine run smoothly during warm-up. Technician B is correct in stating that a rotary idle control valve is used to control idle speed at any engine temperature, adjusting the amount of air bypassing the throttle plate to maintain the desired idle speed under various conditions.

Question 18

The pulse-width control map is being discussed. Technician A says it functions as the look-up table the PCM uses to determine injector pulse width. Technician B says the map values are stored in the PCM's read-only memory and cannot be modified. Who is correct?

Accepted Answer

The pulse-width control map does indeed function as a look-up table for determining injector pulse width, as stated by Technician A. Technician B is also correct in stating that the map values are stored in the PCM's read-only memory, making them unmodifiable under normal circumstances.

Question 19

Which feature is unique to the Bosch K-Jetronic injection system?

Accepted Answer

The Bosch K-Jetronic injection system is unique because it uses a mechanical-hydraulic mechanism where the opening of the air valve directly controls a fuel metering valve, unlike other systems that might use electronic control or manifold pressure to regulate fuel delivery.

Question 20

The modern Motronic electronic transmission control is being discussed. Technician A says it momentarily retards ignition timing during transmission shifting. Technician B says the PCM controls the automatic transmission's shift points using spool-type shift valves. Who is correct?

Accepted Answer

Technician A is correct because the Motronic system, which integrates control of ignition and fuel injection, can momentarily retard ignition timing to reduce engine torque during shifting, improving shift smoothness. Technician B is incorrect because the PCM (Powertrain Control Module) does control automatic transmission shift points, but it typically does so electronically rather than using mechanical spool-type shift valves directly.

Quiz 15: European Bosch Computerized Engine Controls