TTEC 4825 Can System on board N1.

            
                                                       Can System

The CAN bus is a high reliability, high data rate bus for communicating

between electronic devices in situations where high data reliability is

 required. One use of the CAN bus is in the automotive applications where

the CAN bus is being used as a substitute for copper wiring looms in cars.

 In this article we take a look at what the CAN bus is. 

                                          Can System on Board

                             Signal from CAN System without fault and load

                                                          Right indicator

                                                      Left indicator

                                                      Rear wiper

                                                         Stop light

                                                       Fuel pump

                                                    Reverse light

                Every pattern is individual for every load, such: rear light, wipers,
                        windows, sensors, ABS, transmission, head lights etc.
               Both channels should mirror each other as shown in a picture above.

                          CAN L is being pulled down from about 2.5V
                           CAN H is being pulled up from about 2.5V
                  

     This board shows a typical CAN node on a network. All nodes have a

     microcontroller with I/O circuitry, have a CAN controller and a line

     driver which interfaces the CAN L and CAN H differential

     connections to the CAN controller. Some microcontrollers

     have the CAN controller embedded which reduces the cost of the

     node. WE can see that the connections to the CAN node are

     power, ground, CAN H, CAN L and then other connections to I/O

     as required CAN nodes in a car. In this context where

     a node is a complete functioning unit the node is often referred

     to as an Electronic Control Unit or ECU. Here you can see five ECUs:

     an engine temperature sensor, an instrument panel, a switch on a

     brake pedal and ECUs for the left and right hand rear light clusters.

     Although the wires are not shown here all power and grounds are

     connected, and all CAN H and CAN L terminals are connected

     by 100ohm terminated twisted pair wires. In practice you may

     find the foot brake connected to the instrument panel ECU etc.

     A key feature of CAN is reliability, and this is kept to a maximum

     by keeping traffic on the CAN bus to a minimum. In a conventional

     network you might think that the foot pedal would tell the central

     processor on the instrument panel that it has been pushed down,

     and the instrument panel would then tell the light cluster ECUs to

     turn the brake lights on. CAN works differently: When the pedal is

     depressed the brake pedal ECU issues a message effectively stating

     “brake pedal pressed”. This message is issued to the whole bus. The  

     ight cluster ECUs are programmed so that when they see the

     “brake pedal pressed” message on the CAN bus they power up the

     appropriate lamp. This has kept message flow to a minimum, and if

     the instrument panel ECU—or any other ECU—is not working then

     the core important functions of the network are still active. This is an

     example of one type of data exchange for important ‘mission critical’

     data: if your brake lights don’t come on then you could run into trouble,

     or it would run into you. However if this method was employed by all

     devices connected to the bus then the traffic would be quite large—with

     more traffic meaning reduced reliability. So a second technique for data

     exchange is used. Looking at temperature monitoring:  the central

     instrument cluster wants to know what the temperature of the block

     is so that temperature can be displayed on the instrument console

     and—if necessary—the warning light activated. The designers of the

     system will have decided that the temperature needs to be monitored

     at, say, 5 second intervals. So every 5 seconds the central console

     will issue a message saying “can anyone tell me what the block

     temperature is?” The ECU on the block is programmed to look for

     the message “can anyone tell me what the block temperature is?”,

     to then measure the temperature, and reply with a message stating

     “the block temperature is” followed by the temperature data.
                                                       Next

TTEC 4825 CAN System On-Car N2.

                                      Can System on the Range Rover

                Controller Area Network ( CAN ) is an international standard

                for serial communication used to control devices on a network.

                                                     Range Rover 2001

           It is easy to identify the wiring as it is just a twisted pair of thin

           wires. These will  be found all over the vehicle - sometimes in

           with a conventional main loom. The wires are called 'CAN High'

          and 'CAN Low' and it is important that any interface  is connected

           correctly to these wires. 

Because the magnetic field around a wire is circular and perpendicular to the wire, an easy way to amplify the wire's magnetic field is to coil the wire, as shown below:

 

The current passes along the wires creating a magnetic field; this energy is easily transferred from one system to another thanks to a method that is

 similar to the windings in a transformer.

If different cable groups are running parallel between 2 or more components, then separating them will reduce the interference transferred from one to the other. If cable groups need to cross over each other, try to ensure that they do so at 90°. However, Better still, twist the send and return wires together and the net magnetic flux through adjacent turns will cancel each other (provided the twists are even); it will also even out the charge on the wires if subject to an electric field. The intention of this is to reduce the interference between the lines. The tighter the twists the better.

                                                   ABS Control Unit

                   Oscilloscope which I have used, model-"Seintek S2800"

      Taxi Meters require a speed pulse signal in order to calculate the fare.
    Hence on CAN Bus equipped vehicles, a CAN Bus Speed Pulse Interface
    will be required.

                         Chenal A-colour of wire is yelow and brown
                                            Voltage-2V per division
                                             Time-50us per division
                                     Measured voltage Chenal A:
                                            Oscilloscope-2.63V
                                          Multimeter-2.37V DC

                         Chenal B-colour of wire is yelow and black
                                          Voltage -2V per division
                                          Time-50us per division
                                         Measured voltge Chenal B:
                                              Multimeter-2.65V DC

CAN  (Controller Area Network) it  is an international standard for serial

Communication used to control devices on a network. The CAN standard

 governs some of the physical attributes of the network as well as the low

level software communication protocols. Physically the CAN bus itself

 consists of a twisted pair of wires which use differential voltages for data

Transmission.  CAN is designed primarily for control and hence the messages

used are small (8 bytes max).

The basic message structure contains two parts: a message identity and

message data. The actual structure is a little more complicated than this,

with error detection, synchronization and other bitsbeing embedded into

 each message. However one of the great benefits of CAN is that the chips

used take care of these details for you and provide you simply with message

and data information.

Most of the higher specification GPS Navigation systems will require a speed

pulse signal as a minimum. Many also have inputs for illumination and reverse

signals. On CAN Bus vehicles these signals may not be present so a CAN Bus 

Interface will be required.

The reasons for the vehicle manufacturers using CAN Bus are:

1.  Significant reduction in wiring leading to:-

      a) Significant reduction in manufacturing cost and hence retail cost.

      b) Reduction in weight resulting in improved fuel consumption.

2. Reduced number of interconnections hence improving reliability.

I've understood the basic principles behind CAN the next question is

‘exactly how is the basic message structure used to communicate all

this information?’. Here is a key difficulty of CAN. Whilst the general

CAN methodology, the electrical connections, packet structure, error

correction and low level software are specified, the rest is left up to me.

In practice this has meant that every automotive manufacturer has chosen

their own proprietary protocols. Massey Ferguson will be different to Audi

 will be different to BMW etc. The reason for this is probably two fold: firstly

 automotive companies don’t want unauthorized people tapping into the bus

that manages all the safety critical electronic devices in the vehicle, and

secondly diagnostic equipment and training are valuable revenues streams.

For saving the battery power in this car I've found the sleep mode operation.

When an ignition is off, electronic system goes to "sleep" after a short time.

Checking voltages on CAN-and CAN+ to see when bus is "alive" and "down"

The wire is yellow -brown on the ABS Control Unit

1. Voltage, when system in "awake" - 0.29V

2. Voltage, when system in "asleep" - 0.12V

3. When system in "awake" the battery used - 2.35Amps.

4. When system in  "asleep" The battey used - 0.92Amps.

I've used bonnet switch and meaured different at 5 minutes later

*To prevent excess parasitic drain when key is off, a sleep protocol is used

*Not all modules are connected to ignition and see "Ignition off"

*The bus can't go into sleep mode untill all the modules have said

"ready to sleep"

*Any module can transmit a message to "wake up" or become "active"

or "alive".

* When the bus goes to sleep, some modules may still be active( such as

door module for key entry or cabin compartment module)

*Voltage of CAN B-should tell you if it's in sleep mode

*With key off, modules a sleep, internal connections

*Beware ignition switch withj poor connections:and transceivers shut 

down, bus circuit is open

Causes conflicting messages to be sent around the bus and they get 

all confusing.                                              

TTEC 4825 Testing Speed sensors on road, Nissan "Cefiro"

                                     
                                           Speed Sensors on road
                               
                                Nissan "Cefiro" 1996  72000 km

                           Speed is 14 km, signal from 4 sensors are same

Four Channel, Four Sensor ABS - This type of the ABS use a speed sensor on each wheel and

 separate valve for all the four wheels. Maximum braking force is achieved with this type.

             Front speed sensors shows 34 km, rear sensors shows 32 km.
I think, front wheel drive car, in axeleration position of pedal, starts to pull a car forward.
                       This occurs a little loos traction front wheels.

Without axeleration in casual drive, speed sensors shows same speed.
Front-40 km, Rear LH - 40 km, Rear RH - 39 km (small diferent is normal)

                                                           Turn left
                                    The controller monitors the speed sensors at all times. 
                  We can see FR LH and Rear RH - 63 km, FR RH -64 km, RR LH - 62 km

This detailed test show how accurately the speed sensors work when the car is on the move.

Speed sensors monitor the speed at which the vehicle is travelling by sending out precise signals to an Electronic Control Unit.

When the car makes a turn both sides of the car give out a slight difference in speed as monitored by the Scanner.

TTEC 4825 Transmission on the road.

                                        Nissan "Cefiro". Transmission

TCC: Torque converter clutch
ECT: Engine coolant temperature
PCM: Power train control module
PSA: Pressure Switch assembly
TPS: Throttle position sensor
TTS: Transmission temperature sensor
VSS: Vehicle speed sensor

                                            make some choice of test

                              Rear gear ON, solenoids valves A-ON, B-ON

                           Solenoid valves in Parking/Neutral position idle
                                solenoids A-ON, B-ON, over run-OFF

                 Lever position in Drive, Three solenoids valves are ON.

                                                            7 km/h
                     The car is running in first gear, all three valves are ON

Second Gear, valves A-OFF, B-ON, over run-ON, open a littlebit throttle position 0.3V

                        Third gear the throttle is closed, speed is 20 km/h
                                Valves A-OFF, B-OFF, over run-ON

The engine accelerated, throttle open 1.3V, transmission is back to second gear

                                In cruise, the transmission in third gear
 

                                       Fourth gear in cruise, valves are OFF

Accelerating from fourth gear, back to third, position of valves are confirm it

Valves A-ON, B-OFF,over run ON. Transmission in over drive. The throttle is closed

                  Slightly accelerating, no change, throttle open 1.5V,speed is 84 km/h

                        In cruise the transmission in O/D, no change

                        Acceleration, fourth gear starts to work again

              
                                 In cruise, the O/D gear comes again

It is perfect example what's going on and how the transmission works

Electronic transmission controls

Numerous changes have occurred in transaxles and transmissions in the last decade. The demand for lighter, smaller and more fuel efficient vehicles has resulted in the use of electronics to control both the engine and transmission to achieve the fuel efficient results that are required by law. The transaxle/transmission assembly is a part of the electronic controls, by sending signals of vehicle speed to an on-board computer which, in turn, relates these signals, along with others from the engine assembly, to determine gear selection for the best performance.

Sensors are used for engine and road speeds, engine load, gear selector lever position, and the kick down switch operation. In addition, the driving program, set by the factory, is used to send signals to the microcomputer to determine the optimum gear selection, according to a preset program. The electrical part of the equation is usually the solenoids and electrically controlled valves that open and close to allow hydraulic fluid pressure to flow in the desired direction and accomplish a specific task.

The electronics also control the modulated hydraulic pressure during shifting, along with regulating engine torque to provide smooth shifts between gear ratio changes. This type of system can be designed for different driving programs, such as giving the operator the choice of operating the vehicle for either economy or performance.

The transmission's sensors also let the operator of the vehicle know if there are any problems with the system. If the transmission control computer detects a problem it will store a trouble code in memory and it will light or flash a transmission warning lamp (or engine service light) on the dash to alert the operator something is wrong.

Two transmission codes out of repair information; 
Code 45 Damaged or disconnected wiring of the pressure-control solenoid valve

system what the code means Check the solenoid valve connector, check 

the pressure - control solenoid valve itself.

Code 24 Damaged or disconnected wiring of the oil-temperature sensor system
Check the oil-temperature sensor connector, and the sensor itself.

Code: LR solenoid Valve Open
This is open because the cable is unplugged

Code: O/D Solenoid Valve Open
This is open due to the cable is unplugged and car is in the 3rd gear.

1st Problem Testing:
With the vehicle stuck in 3rd gear, we tried shifting the car into different gear
but because all the solenoid valves were stuck open and would not close
therefore the vehicle would not shift and remains in the 3rd gear.

2nd Problem Testing:
During the 2nd test we plugged the cables back into the transmission and
started the car and then we were able to change the gears up and down.
I then used the scan tool to check if the valves were closing or not when
we changed the gears and it did.

Shift Solenoid Malfunction: Describe what would happen if none of the solenoids came "ON". Could the vehicle drive? What gear would it be in?

How fast could the vehicle go? Could it have the Power to climb a hill?
According to the vehicle if all the solenoids were off then the only available gear on the vehicle would be 3rd gear to be used. This is because the 3rd gear does not need any solenoids to be "on" therefore the vehicle will be slow during the initial start and can only use 3rd gear. The vehicle would drive up the hill only if the vehicle is on running start.

Using the proper scan tools or techniques, a technician can retrieve the code
(depending on the manufacturer) in order to help diagnose the trouble.
To get a better understanding of engine and transmission trouble codes, in repair
manual for that year/make/model car.

TTEC 4825 ABS. Speed Sensors On-Car Opel "Astra".

                                            Speed sensors On-Car

                                                       Opel "Astra"

                                              Brake Master Cylinder

                Hydraulic module, Electronic Control Unit, Hydraulic pump

                                             Hydraulic Control Unit
Two lines from master cylinder (in), Four lines to wheel cylinders or calipers (out)

           Behind of Hydraulic Control Unit we can see pump and motor assembly

     In order to test a speed sensor, we need to locate the connection plug by following
the wire from the speed sensor it self.( In different cars-different places)

 Hall effect sensors elements generate a voltage that varies by relation to the
changing magnetic poles.

We can see how the wheel speed sensor tone ring is built into the
wheel bearing  assembly, unlike other wheel speed sensor setups
where the tone ring is on the outside of the outer CV joint housing,
axle or hub.

                                  Inductive or magnetic sensors.
 

Wheel speed sensors consist of a toothed rotor and a pickup.Wheel rotation sends input signals to the ECU, which processes them and controls the hydraulic control unit.

A wheel sensor consists of a toothed rotor that rotates with the wheels, and a pickup. As each tooth of the rotor passes the pickup, a small voltage is induced in the pickup. These pulses are sent as input signals to the electronic control unit which processes them, to operate the hydraulic control unit.

A magnetic pick-up has a magnet which changes reluctance as the
magnet is near or far from the iron on the teeth of the ring.

                                            Slow rotation of wheel

                                             Faster rotation of wheel

                                      More faster rotation of wheel.

                 The faster the wheel turns, the more voltage it produces. 

The signal pulse is generated when a tooth passes under

the magnetic tip of the sensor. The tooth passing through the

sensor’s magnetic field causes the sensor to act like a little generator 

and produce an alternating current signal that increases in frequency 

and amplitude in direct proportion to wheel speed. If we look at the

signal on an oscilloscope, it should look like a nice even sine wave 

with all the up and down humps in the waveform evenly spaced

and the same height.

A good wheel speed sensor will typically produce an alternating current (AC) voltage reading of 50 to 700 MV when the wheel is turning one revolution per second.

If the scope pattern produced by the sensor is flattened (diminished amplitude) or is erratic, it usually indicates a weak signal caused by an excessively wide air gap between the tip of the sensor and its ring, or a buildup of metallic debris on the end of the sensor. A weak signal 
can also be caused by internal resistance in the sensor or its wiring circuit, or loose or corroded wiring connectors.

Salt at Fault
In the case of the Chevy/GMC recalls, salt water was apparently working its way into the hub assembly at the sensor hole and attacking the tone ring. In many instances, the problem was not bad enough to set a fault code and turn on the ABS warning light. But it was bad enough to generate misleading wheel speed readings and trick the ABS system into kicking in and pulsing  the brakes when ABS was not needed.

Magnetic sensors can also pickup metallic wear debris from the rotors and pads, causing the sensors to read erratically and confuse the anti-lock brake system. Cleaning the sensors and resetting the air gap can often restore normal operation. But if the tone ring is corroded or damaged, it must be replaced.

Reading ABS codes requires an ABS code reader, scan tool or scanner software that can access the ABS system. An inexpensive OBD II code reader or an entry-level scan tool designed for a do-it-yourselfer won’t work here. You need a professional tool designed for ABS diagnostics, or a digital storage oscilloscope to look at the wheel speed sensor waveforms.

If there are no codes, but the vehicle owner complains about the ABS system engaging when braking (noise, vibrations and pedal pulsations), the problem is likely a bad wheel speed sensor. But which one? That’s where a scope can really help you identify which sensor is acting up. Connect the scope to the sensor leads and spin the tire by hand. If you get a good clean signal, move on to the next WSS sensor and so on until you find the one that is generating a bad signal.

You need to make sure you have diagnosed the fault correctly on vehicles with ABS wheel speed sensors because the replacement parts are not cheap.