Cab and Hood Flashcards
When inspecting the key condition, what should you look for?
Inspect the vehicle keys for wear, nicks, bends, or other damage.
When inspecting the ignition switch, what should you ensure
Ensure that the ignition switch is securely mounted and operates smoothly without binding and provides constant port a the accessory, on, and crank positions.
I the truck is equipped with a push-button start switch, how should it operate?
It should operate easily without sticking while properly closing the cranking circuit when depressed.
What is a driver ID code or card used for?
It is used with trucks that have a keyless ignition system
Describe the earlier lamps or indicator lights.
Earlier lamps were small, round lights that were color-coded for their system; yellow for a warning or caution in a non-safety-related system and red for safety-related system warnings.
What systems still use lights?
Major or Safety related systems.
What kind of lights do many non-safety systems use?
Light Emitting Diodes (LED) behind a pictogram of the system it is monitoring.
Why are LED lights such an improvement?
This improvement allows for less electrical current usage in the instrument panel and more reliable operation.
What are the benefits of the self-check feature?
It illuminates all warning lamps when the ignition switched first switched to the on position.
This lets the driver and/or technician know that the lamp and circuit are operational.
What are alarms and buzzers used for in some systems?
For low-pressure (which is mandatory) and for low oil pressure.
The low pressure must sound when the system air pressure drops in below 50 percent of the governor cut-out pressure (approximately 60 psi)
When checking the operation of instruments/gauges and panel lighting, what will a short circuit in the sending unit wire to the gauge do?
It will lower resistance in that circuit, causing the gauge needle to read high.
What will a short circuit to ground in a sending unit wire cause?
It will cause an overload of current to the gauge, which will burn out in a very short time.
Although not considered an official criterion for out-of-service (OOS) status what will a malfunctioning oil pressure gauge cause?
It may be cause for an inspector to deadline a vehicle because a no-oil pressure condition can rapidly destroy and engine.
In performing a proper and thorough check of a vehicle’s instrument panel, as a part of any PMI, what happens when the ignition is first turned on?
Electronic gauges perform a self-test by sweeping the needles.
What does PTO stand for?
Electronic Power Take-Off
How do modern diesel engines mange idle speed and shutdown?
By computer control. This is sometimes a PTO function when the engine speed is set to operate auxiliary equipment.
How can idle speed be raised and lowered?
By the use of a toggle switch provided on the dash.
How does a programmed engine shutdown occur?
After the desired time interval, when the desired time has elapsed, without input from the throttle pedal of the clutch pedal, the engine will shut down automatically.
What would you use to change the programmed time?
An electronic service tool. (EST)
How does the automatic stop/start features work?
Most engine management Systems have stop/restart features that expand the normal idle shutdown feature to further reduce idle time.
They will automatically stop and restart when require to hold engine temperature about a programmed specific value, maintain the battery charge level, and to keep the cab/sleeper at a temperature level programmed into customer parameters.
What are other benefits of having automatic stop/start features?.
Other benefits claims are reduced emissions, noise, and engine life.
What conditions must be in order for the stop/restart feature to be enabled?
- One OEM system requires that the ignition switch be on, the engine idling with the idle shutdown timer enabled, the hood closed, the transmission in neutral or park, the parking brake set, and the master cruise switch in the on position.
What happens when the system determines to start the engine?
Based on sensor inputs, the active lights illuminates and an alarm in the engine compartment sounds, and the engine cranks.
If the engine fails to start, will a second attempt occur?
Yes, a second attempt will occur in 45 seconds.
At startup, how many RPMs does the engine ramp up to?
1,000 RPMs
What happens if the restart is prompted by input from the cab temperature sensors?
After about 30 seconds, the climate control system will turn on to manage the cab/sleeper temperature.
Engine shutdown can also occur to prevent damage to the engine from lack of lubrication or overheating conditions.
What is Failure Strategy?
The way in which the engine electronically responds to a potentially damaging conditionally
1. Failure strategy response levels are programmable and typically would be driver alert-(lowest level), engine ramp-down and engine shutdown -(highest level)
What level of failure strategy do manufacturers recommend programming?
The highest level failure strategy, except for emergency vehicles, such as fire trucks are programmed with low-level failure strategy. An EST can be used to check the programmed failure response.
When checking the HVAC system, what should it be able to do?
The HVAC system should be able to regulate the temperature in the cab and sleeper.
What should the blower motor be able to do?
The blower motor should operate at all speeds.
What should the blower be able to do?
The blower should produce an adequate flow of air and should not be abnormally noisy.
What should the technician hear with the engine idling and what are the steps he should take?
- With the engine idling, the tech should hear the A/C compressor clutch engage when air conditioning is selected.
- Raise the engine to about 1,500 rpm and close the doors and windows.
- Turn the blower to high and select the coldest temperature.
- Run the system for about 10-15 minutes and compare the temperature of the air at the outlet nearest the evaporator with specifications in the service manual.
- Check the sleeper controls the same way.
If the truck has an ATC, what should the outlet temperature be?
The outlet temperature should be within several degrees of the set temperature.
What cab and chassis accessories should be tested during a road test.
A vehicle onboard radar (VORAD) collision warning system (CWS) has to be tested on the road as well as with an EST.
What is the typical process for checking DTCs?
Use a handheld EST of a laptop computer to access the data bus; then check for, record, and clear DTCs.
What are the DTCs controlled and monitored by?
Electronic modules.
What is used to facilitate troubleshooting intermittent problems that either do not generate codes or do not store a code without a clear reason?
Most systems will accommodate a snapshot readout from the electronic control module (ECM) to facilitate troubleshooting intermittent problems that either do not generate codes or do not store a code without a clear reason.
What do control modules store?
Control modules store fault doces against parameter identifications (PIDs)
How does the technician access the databus?
To access the databus, the technician connects a diagnostic reader to the American Trucking Association (ATA) connector.
Once the diagnostic reader is connected, what will most systems allow two-way communications for reading?
Most systems allow two-way communications for Reading system parameters, calibration data, diagnostics, data programming, recalling faults, and audit trails.
How do some electronic systems display active codes?
By blinking two-digit numerals on the instrument panel indicator.
Diagnostic tests are menu-driven, so what should they be used to identify?
To identify the FMIs (Fault Mode Indicators).
Once the problems have bee corrected, what should be done with the inactive fault codes?
The inactive fault codes need to be cleared. ESTs can be used to clear these codes.
What are ESTs capable of reading the chassis databus connected to?
ESTs capable of reading the chassis databus are connected to the on-board electronics by means of an SAE/ATA J1587/J1708/1939 6 pr 9-pin Deutsch connector in all current systems.
