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23 Cards in this Set
- Front
- Back
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What is the purpose of the pcm ?
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to pulse the fuel injectors and fire the spark plugs at the correct time.
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What is the purpose of the oxygen sensor ?
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to determine if the air/fuel mixture is rich or lean
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Why does the computer need to know if the air/fuel mixture is rich or lean ?
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to determine whether to add to fuel injector pulse duration or subtract from it (also known as positive or negative fuel trim).
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What is the function of the map sensor ?
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to determine the engine load and report it to the pcm so that the computer can adjust the air/fuel ratio accordingly.
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What is the purpose of the tps ?
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To tell the pcm where the throttle plate is relative to time and position so that the computer can adjust the air/fuel ratio accordingly.
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What is the purpose of the coolant temperature sensor ?
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to determine the temperature of the engine and report this information to the pcm so that it can use this piece of information to calculate injector on time.
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What is the purpose of the crankshaft position sensor ?
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to inform the pcm where the pistons are relative to time so that the pcm will know exactly when to pulse the fuel injectors and when to fire the spark plugs.
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What is the purpose of the air flow meter ?
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to determine how much air is flowing into the engine intake manifold and inform the pcm of this information so that the pcm can use this to adjust the air/fuel ratio accordingly.
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How often should the oxygen sensor switch between rich and lean when being viewed from from a scope ?
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5 times every 10 seconds
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What controls both the fuel injectors and ignition coil(s) ?
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The powertrain control module has transistors inside of it that switch on and off the fuel injector and ignition control circuits based upon sensor input data and the computer program stored inside of the pcm.
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What conditions need to be met in order for the engine control system to go into closed loop status ?
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a. both upstream oxygen sensors are cross-counting
b. coolant temp is greater than 150F c.one minute has elapsed since start-up d. tps position is less than 80% |
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When analyzing a fuel injector waveform with a scope, what is most likely the cause if the voltage does not spike high enough when the injector opens the ground side of the fuel injector circuit.
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The fuel injector coil is probably shorted if this is the case.
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When analyzing a throttle position sensor waveform, what happens if you find a glitch in the waveform throughout the range of it's operation ?
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The sensor is faulty and should be replaced.
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When analyzing a fuel injector waveform with a scope, what is most likely the cause if the voltage does not spike high enough when the injector opens the ground side of the fuel injector circuit.
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The fuel injector coil is probably shorted and therefore you should replace the fuel injector.
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All sensors fall into five families. Name all five of them.
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1. Potentiometers
2. Thermistors 3. Switches 4. Signal Generators 5. Voltage Generators |
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The absence of a computer code means that the sensors and actuators are ok. True of False
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False
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How many wires does the potentiometer have ? Describe them.
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3 wires
a reference voltage wire a signal voltage wire a ground voltage wire |
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Excessive exhaust emission can be caused by:
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engine mechanical, fuel, ignition, and engine control system problems
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An erratic signal from the ect sensor due to a low coolant level can cause:
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upset air/fuel mixtures
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If the engine never reaches normal operating temperature, what could this cause ?
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The engine may not ever go into closed loop operation.
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If coolant enters the exhaust system through a combustion chamber leak, what can this cause ?
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it can contaminate the O2 sensor and eventually cause it to stop working.
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When you operate the brake switch, what happens to the torque converter lockup clutch ?
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the brake switch when engaged commands the pcm to unlock the torque converter.
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An exhaust leak upstream before the O2 sensor can cause:
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erroneous O2 sensor readings which can lead to incorrect air/fuel ratios and this in turn can prevent the system from going into closed loop operation
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