Question

1. two technicians are diagnosing an engine performance issue. the truck has a mil on with a code of p0128. technician a says a stuck open thermostat may be the cause. technician b says a faulty coolant temperature sensor may be the cause. who is correct?

a. technician a
b. technician b
c. both technicians
d. neither technician

1. at what speed will the pcm usually turn off electric cooling fans?
2. all the following may cause the pcm to run the electric cooling fan on high except?

a. ect reaches 110 degrees c
b. a/c refrigerant pressure exceeds 240psi
c. vehicle is moving over 60mph
d. certain dtcs are set

1. the coolant temp warning light comes on when the ect reads between __ and __ degrees.
2. a radiator has been replaced and now the customer complains of a poor idle. the technician notices erratic temperature readings from the ect while monitoring current data. what is the most likely cause?

a. air in the cooling system
b. collapsed upper radiator hose
c. wrong coolant used
d. radiator cap installed incorrectly.

1. when the engine is hot, where does the excess coolant go when it expands in the radiator?

a. drains on the ground
b. gets trapped in the radiator
c. into the surge tank
d. none of the above

1. air in the cooling system will cause all the following concerns except

a. erratic temperature readings
b. poor heater operation
c. cooling fan failure
d. overheating

1. what is the purpose of a coolant bypass/bypass hose?
2. which of the following cooling system configurations is the least likely to form galvanic corrosion?

a. aluminum radiator, cast iron block and cast - iron head
b. aluminum radiator, aluminum block, and an aluminum head
c. aluminum radiator, cast iron block, and an aluminum head
d. brass radiator, cast iron block and a cast iron head.

Explanation:

Step1: Analyze question 1

A stuck - open thermostat and a faulty coolant temperature sensor can both cause engine performance issues related to the MIL code P0128. So both technicians are correct.

Step2: Analyze question 2

The PCM usually turns off electric cooling fans when the vehicle speed exceeds a certain value. But the question is incomplete as no options are given for a proper answer.

Step3: Analyze question 3

ECT reaching 110 degrees C, A/C refrigerant pressure exceeding 240PSI, and certain DTCs being set can cause the PCM to run the electric cooling fan on high. Vehicle moving above 60mph is not a typical reason for the PCM to run the fan on high.

Step4: Analyze question 4

The coolant temp warning light comes on when the ECT reads between certain temperatures. But the blanks are not filled with options in the question for a proper answer.

Step5: Analyze question 5

Erratic temperature readings from the ECT after radiator cap replacement are likely due to air in the cooling system.

Step6: Analyze question 6

When the engine is hot, excess coolant expands into the surge tank.

Step7: Analyze question 7

Air in the cooling system can cause erratic temperature readings, poor heater operation, and overheating, but not cooling fan failure.

Step8: Analyze question 8

The purpose of a coolant bypass/bypass hose is to allow coolant to circulate when the thermostat is closed, maintaining some coolant flow for engine warm - up and other functions. But without options, a proper answer can't be given.

Step9: Analyze question 9

Aluminum - to - aluminum combinations are less likely to form galvanic corrosion compared to combinations with different metals. So an aluminum radiator, aluminum block, and aluminum head is the least likely to form galvanic corrosion.

Answer:

1. c. Both Technicians
2. No answer (incomplete question)
3. c. Vehicle is moving above 60mph
4. No answer (incomplete question)
5. a. Air in the cooling system
6. c. Into the surge tank
7. c. Cooling fan failure
8. No answer (incomplete question)
9. b. Aluminum radiator, aluminum block, and an aluminum head