A Answer A is wrong. A leaking fuel injector will cause a rich condition.

B Answer B is wrong. A faulty pressure regulator will cause a rich fuel condition.

C Answer C is wrong. A faulty ECT will cause a rich fuel condition.

D Answer D is correct. A stuck closed thermostat will cause a vehicle to overheat.

A Answer A is wrong. Both technicians are correct.

B Answer B is wrong. Both technicians are correct.

C Answer C is correct. An oxygen sensors heater circuit is designed to bring the sensor to operating temperature and closed loop quickly. It senses oxygen content in the exhaust when it is in closed loop.

D Answer D is wrong. Both technicians are correct.

A Answer A is wrong. A stuck open EGR valve will cause an engine to stumble or stall.

B Answer B is wrong. A stuck closed EGR valve will cause an engine to ping.

C Answer C is wrong. Neither technician is correct.

D Answer D is correct. Neither technician is correct.

A Answer A is wrong. A Manifold Absolute Pressure Sensor senses the pressure in the intake manifold indicating engine load.

B Answer B is wrong. The Mass Air Flow Sensor senses air volume in the air tube to indicate engine load.

C Answer C is correct. Both Technicians are correct.

D Answer D is wrong. Both Technicians are correct.

A Answer A is correct. An Air / Fuel Sensor is designed to reach and keep a vehicle at Stoichiometry.

B Answer B is wrong. Stoichiometry is 14.7:1 air to fuel mixture.

C Answer C is wrong. Technician A is correct.

D Answer D is wrong. Technician A is correct.