Sunday, September 19, 2010
Tuesday, September 7, 2010
Scan Tools
Using A Scan Tool
Monday, September 6, 2010
Scan Tool Observations
Which Vehicle Are you using? Land Rover
Which Scan Tool are you using? Auto Boss
2.2 What different functions are available on the scan tool to examine the CAN system?
Primary Ignition, secondary Ignition, Multimeter, DSO, Engine Analyser
2.3 List the different systems that are controlled by CAN? (note which are high speed and which are low speed)
High
ABS/ TCS/ Engine Control/ EPS
Low
Tv, Windows, Body Control
CAN Multiplexing worksheet
1.1 Locate the Range Rover or other suitable vehicle with easily accessible CAN system twisted wires. Which vehicle do you have? (Year, Make, Model)
2001 Landrover
1.2 Locate a twisted wire pair. Describe where the wires are located. The Twisted Wire Pair were located inside the engine bay on the Hydraulic Control Unit
1.3 Record the waveform of one of the wires below. ("make sure your time is small enough so you dont have aliasing")
Colour of wire: Yellow
Time per division: 2 Seconds
Voltage per division: 0.5V
1.4 Record the waveform of the other wire.
Colour of wire: Black
Time Per Division: 20ms
Voltage per division: 1V
1.5 What is aliasing? Describe it: When a digital image is viewed, a reconstruction-also known as an interpolation-is performed by a display, and by the eyes and the brain. If the resolution is too low, the reconstructed image will differ from the original image, and an alias is seen. Aliasing can be caused either by the sampling stage or the reconstruction stage; these may be distinguished by calling sampling aliasing prealiasing and reconstruction aliasing postaliasing
1.6 How do you know these waveforms are not alisaling?
Because they are symmetrical when placed together, and this is what it should like.
1.7 In the 1.3 Waveform above, what is the main voltage on the line? 2.5V
What is the other voltage on the line, when the voltage is pulled up or down to "talk"?
1.8 In the 1.4 Waveform above, what is the main voltage on the line? 1.5V
What is the voltage on the line, when the voltage is pulled up or down to "talk"?
1.9 Observe the signals in 1.3 and 1.4 with a voltmeter. Compare it with DC volts or AC volts setting . Which setting would tell you if the signal is switching. Explain. DC Would tell me if the signal is switching because I would get a straight line when it is either on, or off, while analogue will give me a curvy line.
Monday, August 23, 2010
On Car Exercises
Codes and diagnostics
Pick two transmission codes out of repair information, and describe what the code means and what mailfunction would cause the code:
Code: LR Solenoid Valve Open
Code:OD Solenoid Valve Open
Diagnosis:
For each code listed above, discuss what tests you could run to diagnose the problem.
1st problem testing:
With the vehicle stuck in 3rd gear, we tryed shifting the car into a different gear. But because all the solenoid valves were stuck open and wouldn't close, the vehicle would not shift and it stayed in 3rd gear.
2nd problem testing
For the 2nd test, we plugged the solenoid cable back into the transmission and turned the car on. We were then able to change up and down gears. We then used the scan tools to make sure the valves were closing when we changed gears and they did.
Shift Solenoids
Shift Solenoids
Which solenoids are "on" when this vehicle is shifted into drive and starts out in first gear?
Both Solenoids are on on when this vehicle is in 1st gear.
Which solenoids are "on" when this vehicle automatically shifts into second gear?
When the vehicle switches to second gear, the second solenoid is on
Which solenoids are "on" when this vehicle automatically shifts into third gear?
No solenoids are on when this vehicle is in 3rd gear
Which solenoids are "on" when this vehicle automatically shifts into fourth gear?
The 1st solenoid is on when this vehicle is in 4th gear
Shift solenoid mailfunction
Describe what would happen if none of these solenoids came "on". Could the vehicle drive? What gear would it be in? How fast could it go? Could it have the power to climb a hill?
If all the solenoids were off in this vehicle, the only gears this vehicle could use would be 3rd gear. That is because in 3rd gear this transmission does not need any solenoids on. The vehicle will be slow and sluggish at start off and could only use third gear. As for climbing a hill, the vehicle could drive up it if the vehicle had a running start.
Electronic Transmissions and Scan Tools
PCM: Power-Train Control Module.
The Power-Train Control Module is a combined control unit, consisting of the Engine Management ECU and the Transmission Control Unit
TCC: Torque Converter Clutch
The Torque Converter Clutch acts as the equivalent of a manual clutch. It separates the load from the power source
TPS: Throttle Position Sensor
The Throttle Position Sensor or TPS is a sensor that monitors the position of the throttle in an internal combustion engine
ECT: Engine Coolant Temperature
The Engine Coolant Temperature is a sensor that turns on the electric fan or sends a signal to the operator when the coolant reaches a temperature above it's recommended parameters
VSS: Vehicle Speed Sensor
Detects how fast the wheel is rotating by using a rotor tooth and sensor that sends a signal to the ECU
PSA: Transmission Range Fluid Pressure Switch Assembly
The PSA is a sensor that detects all the shift points in the shifting of the gears in an Automatic Transmission
TTS: Transmission Temperature Sensor
The TTS lets the ECU know how warm or cold the transmission fluid is and adjusts the timing of the shifts.
Using a Scan Tool
1. A/con Switch Off
2. BPP Off
3.Power Steering Pressure Off
4. MT/AT discrimination Off
5. Neutral/ Clutch Switch On
6. Refridgerant Press Switch Off
7. Trans Range (DLC) On
8. Ten Terminal (DLC) On
9. Cooling Fan Control (Hi) Off
Using the scan tool on the vehicle you have been assigned to. Go to the actuator test screen. Note below what component you have tested and what happened when you tested that component and the test results.
1. # of Continuous DTCS in modulator 3
2. ABS Valve CTRL Relay on
3. ABS warning lamp status off
4. BAT positive volt 14.69
5. Brake Switch In off
6. Hydraulic Pump Motor x2 off
7. LF ABS inlet valve off
8. LF ABS output valve off
9. LF Wheel Speed Sensor 0kmh
10. RF ABS inlet valve off
11. RF ABS Output Valve off
12. RL Wheel Speed Sensor 0kph
13. RR ABS output Valve off
14. RR Wheel Speed Sensor 0kph
ABS Wheel Speed Sensors
How did you conclude the wheel sensors were analogue or digital?
Rear Right
Rear Left
Using an oscilloscope connect it to a wheel sensor and record the pattern shown, If the sensor is a analogue sensor then just connect the probe and spin the wheel. If the sensor is digital you will need to have the ignition before you turn the wheels. (Left Image Front Wheel Sensor), (Right Image Rear Wheel Sensor)
Using the frequency scale on a multimeter. Turn the wheel approximately the same speed as in the above test. Note the frequency and compare it to the graph you drew above.
Frequency Observations....
Sunday, August 22, 2010
Relay Waveforms
Explain what is happening above.
Explain what is happening in the waveform.
When I turn the key on, the ABS warning lamp comes on. This is because the ABS is doing a self test. The system relay switch closes and voltage runs through to the Motor Pump Relay and Power at the pump jumps to 12V, and then after a few seconds switches off and voltage at the pump goes back to 0V. The lamp then goes off, indicating that everything is fine with the ABS.
Catch an oscilloscope pattern when an ABS solenoid has actuated. What is the pin and name of the solenoid? How did you do it?
I caught this pattern by slamming on the brakes at 800ms. The voltage then went up to 5v and stayed. This means the solenoid was off until I slammed onto the brakes, then the solenoid turned on, and this is how I got my reading of 5V.
Draw the patternABS Relays
ABS Demonstrators
Which wheel is this?
Which wheel is this?
Right Front
Are all the waveforms exactly the same? Yes/ No. Discuss what are the differences, and what can cause the differences between the waveforms.
Left Rear:
Right Front:
Right Rear:
Can a multimeter be as accurate as in finding problems with the wheel speed sensors as an oscilloscope? Yes/ No
ABS Wheel Sensors
ABS Solenoid Valves
Using the picture as a guide, which of the following gives the correct condition of the inlet and outlet solenoid valves under normal braking?
Answer = B.
When the brakes are being used normally and there is no ABS action required, the inlet valves are held open, and the outlet valves are held closed.
Which of the following gives the correct condition of the inlet and outlet solenoid valves when the ABS is operating to reduce wheel back pressure?
A: Inlet Valve Open Outlet Valve Open
B: Inlet Valve Open Outlet Valve Closed
C: Inlet Valve Closed Outlet Valve Open
D: Inlet Valve Closed Outlet Valve Closed
Answer = C
When the ECU detects that the pressure at a wheel needs to be reduced to prevent skidding the outlet valve is opened by a signal from the ECU.
Which of the following gives the correct condition of the inlet and outlet solenoid valves when the ABS is operating to hold back pressure?
A: Inlet Valve Open Outlet Valve Open
B: Inlet Valve Open Outlet Valve Closed
C: Inlet Valve Closed Outlet Valve Open
D: Inlet Valve Closed Outlet Valve Closed
Answer = D
When the ECU detects the sudden decceleration of a wheel, indicating the wheel is about to skid, it signals the hydraulic control unit to hold the pressure at that brake. The outlet valve is already closed and the signal from the ECU closes the inlet valve.
Which of the following gives the correct condition of the inlet and outlet solenoid valves when the ABS is operating to increase wheel back pressure?
A: Inlet Valve Open Outlet Valve Open
B: Inlet Valve Open Outlet Valve Closed
C: Inlet Valve Closed Outlet Valve Open
D: Inlet Valve Closed Outlet Valve Closed
Answer = A
After the pressure at the wheel has been reduced and the wheel is no longer about to skid, the pressure can be increased: The outlet valve is closed so that fluid cannot pass to the accumulator and pump. The inlet valve is opened so that pressure can be increased.
In the four cases above state when the ABS motor will be working?
When the ABS is opening solenoid valves and trying to reduce pressure
ABS Wiring and Operation
2. Rear Wheel Sensor
3. Toothed Rotor
Wiring Diagram Practice
There are a number of components in the ABS systems that are also used for fuel injection. These are mostly speed sensors e.g. wheel speed and engine speed
Using the diagram in the workshop manuals identify the wheel speed sensors and list their wire colours for each sensor.
Front Right: B/W
Front Left: G/R
Rear Left: L/P
Rear Right: Y/BR
On the ABS wheel sensor what is the reason for the braded wire?
So it can be used for shielding purposes or used alone in flattened form as a shielding strap (ref There are many advantages of using braded wire for the wheel sensor. ref www.answers.com/topic/braided-wire
- Power: Braded wire can carry more power because it has a higher surface area. It can also used to carry large amounts of power because it dissipates heat much quicker when there is space between the wires.
- Sound: When sound is introduced to a piece of wire, a vibration occours, disrupting the signal. This is bad for the wheel sensor because the sensor is constantly operating and sending signals to the ECU. With braded wire, voltage gets dissipated alot quicker as the signal is sent to the ECU.
- Flexibility: Braided wire is often used for devices that need to be compact because of it's greater flexibility. This is a great advantage because the hose is constantly moving and twisting and braided wire is much more reliable.
Identify and list all the fuses that are used by the ABS circuit.
F14 fuse box, FL main, Y-G, Gauge 10A, Dome 20A, Stop 15A (brake) and ECU.
Identify the earths for the ABS control unit and ABS motor and their wire colours and pin numbers
10B W-B/ 7B W-B/ 1A W-B
On the wiring diagram for the ABS actuator, identify which solenoids control which wheel cylinder. Then note the wire colours and pin numbers.
Front Right Wheel Pin Number: 2B/6B Wire Colour: R-W/R-G
Front Left Wheel Pin Number: 3B/ 7B Wire Colour: L-R/ L-W
Rear left Wheel Pin Number: 1B/5B Wire colour: BR-W/BR-R
Rear Right Wheel Pin Number: 4B/8B Wire Colour: G-B/ G-Y
ABS Braking Off Car Exercises
Below are some possible causes for damaging an ECU.
- Spiked by careless welding, i.e. MIG welding without disconnecting the battery. True/False.
True. When welding on cars there are two basic rules to follow: Always unhook the Positive and Negative cables from the battery terminals. Set a grounding clamp as close as possible to the area around you are welding with a clean connection.
- Enclosure seal damaged and with obvious sign of water ingress
True. If the enclosure seal is cracked or damaged, water or other substances have a way of getting into the compartment and damaging the ECU
- Obvious signs of mechanical damage to the enclosure
True. Mechanical damage can destroy the ECU depending on what and how the damage was occurred in the first place.
Often the ECU will be misdiagnosed as faulty, usually because the technician is inexperienced in fault finding.
- Faults are much more likely to be with connections or sensors. True/False.
True. A chipped rotor tooth, damaged sensor or cracked or broken connection hose will send no, or false information to the ECU. Also, as the ECU has hundreds, or even thousands of processes at a time, it is much more common that a sensor or connection has become faulty rather then the ECU itself being faulty.
Discuss how these ECU issues should be incorporated into diagnostic practices to test an ABS system.
When diagnosing faults with the ABS system, make sure all sensors and in working order and no damage has occurred to the connection hose. Also checking the condition of the coil in the wheel sensor for open circuits may lead to the ECU getting false information. If able, acquire a scan tool and check for faulty circuits before replacing parts. Also make sure the wheel sensor air gap should be around 0.4mm to 1mm.