Electronic Transmission and Scan Tool

Abbreviations which are commonly used for this subject description:

PCM = Powertrain Control Module
TCC = Torque Converter Clutch
TPS =Throttle Position Sensor
ECT = Engine Coolant Temperature Sensor
VSS = Vehicle Speed Sensor
PSA = (Transmission Fluid) Pressure Switch Assembly
TTS = Transmission Temperature Sensor

Vehicle: Toyota Caldina, 1998Y, 1.8 L

The solenoids S1 and S2 control forward clutch and direct clutch relatively, but the S3 solenoid controls the lock-up clutch of the torque converter. As it is signed on the diagram all these solenoids are controlled by PWM signal. Pressure in the line is altered according to the TPS position, engine coolant temperature, RPMs. This sort of adjustment provides fast shift without clutch slipping while accelerating sharply and soft gear shift while accelerating gently or cruising. To avoid irritating situations of gear changing up-shift and down-shift the overdrive button is used. Once O/D is off only first three gears are in use. This provides higher torque in the speed frame 50 to 60 km/h eliminating unnecessary up-shift.

 From comparison between the photos when O/D is "on" and "off" we can conclude that lock-up solenoid comes to action much earlier when all four gears are in use, 1850 RPMs compared to 2250 RPMs. This is the way to gain in terms of economical efficiency.
This table below is shift chart for Toyota Caldina Gear Box which is built on the basis of scan tool reading above. Video clips were trimmed to make it easier to see how solenoids come to action.

Case number 1: Code DTC 14 (ECT signal voltage is low)

This code appears if ECT sensor voltage is lower than 0.3 V what indicates that engine coolant temperature is above 140 C for one second. Also this code appears if ECT sensor is shorted to ground.

Diagnosis:

Make sure what is the real engine coolant temperature. If the temperature is normal check the connection of the sensor and harness state. Use voltage drop for this procedure. “Temperature to resistance” test of the sensor will help to eliminate miscalled sensor. Only if the sensor is ok and there is no shorted harness the ECU can be suspected as faulty.

Case number 2: Code DTC 21( TPS signal voltage high)

If voltage from TPS is higher than 4.92 V the DTC 21 will appear. Problems with sensor ground can cause this code appearance. To eliminate wiring and the ECU disconnect the TPS from supply voltage, the sensor signal should go low.

Diagnosis:

While the throttle is closed check the voltage out. It should be within 0.25 to 1.25 V. Then disconnect harness and read re-check voltage out which should be below 0.2 V. Use voltage drop test for checking ground. Also check the harness for proper connection. If all this aspects show that there is no faulty devices then only the ECU can be suspected as faulty.

CAN-Multyplexing Worksheet

We've got Land Rover 2003 model which is on the photo. This twisted pair connected to the ABS connector is CAN system.
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Have chosen 50us per division on the time axis scale and 2v per division on the voltage axis scale we captured this pattern:

  Here there are channel A which is L-CAN (yellow/black wire) and channel B which is H-CAN (yellow/brown wire).
Thanks to using double channel oscilloscope we can watch how high and low data signals oppose each other. Also, it's easier to justify that there is no aliasing affect in this case. Aliasing as event is situation when two signals with different frequency distort each other like one signal pattern lies above the other signal pattern. Some time it happens with signals which frequencies are as much as twice different. For instance the signal of 7 KHZ can be repeated in form and shape at the frequency of 14 KHZ. If equipment we use for sampling interpolates these two signals we can get wrong reading as some sort of combination. Good measuring equipment has special filters to avoid this misreading. Visual affect for digital signals aliasing can be understood easier on the example of digital picture pixels which are diffused slightly. That's why digital electronics tends to use higher frequency for higher definition.
For Ch. A main voltage in the line is 2.8 V and "talking” voltage is 3.6 V
For Ch. B main voltage in the line is 2.8 V and voltage to "talk" is 1.6 V

Below are photos of our attempts to get reading from the voltmeter in DC mode:

As these picture shows in comparison with oscilloscope reading above there is no sense to perform these measurements. They do not provide any useful information about modules and devices communication.

Scan Tool reading photo and video below express much more useful information reading. Video illustrates how by using “AutoBoss” scan tool we can simulate signal in to operate with certain device via CAN system. And once again, this process clarify that architecture of the system is divided onto the inputs, communication, and outputs. Eliminating any stages from this we can localise fault faster and more efficiently.
"As invaders" we got into the actuators department of “AutoBoss” scan tool, then chose a windscreen wiper and activated it:

Even though on the first photo we can see only on-board equipment available for scanning, the opportunity to test different CAN systems such as engine CAN system, ABS CAN system, VSA CAN system, suspension CAN system e. t. c. still exist. Eventually how far you can go into the system depends on the software of the scan tool. We didn't show others experiments video due to time frame during practical session although we activated also headlights, washer motor and windows....
The systems listened above are different in terms of the speed of the particular system. This is because the hierarchy of the vehicle modules. Engine, ABS and Stability control systems, Transmission system, SRS system have 128-1024 Kb per sec. Infotament system is slower and can be about 12b Kb per sec. Body system can be even slower, up to 32 Kb per sec. Manufacturers produce higher speed systems for most important from safety point of view systems and slow speed systems for the systems with less priority. For information exchange purposes a gateway is used between the systems. This gateway allows interfacing of different speed systems.

 

These two diagrams above Range Rover rated as fast CAN Bus system. And thes two diagram below company named as K Bus, I Bus with low speed:

 

There is Honda Accord Multiplex system wiring diagram below:

G- is Gateway which allows to interface modules with different speeds without aliasing and signals distortion. This is very important for data transferring.

Having been experimented on the CAN system we did not put it into the sleep mode because of connection of scan tool. However, when everything is deactivated, CAN system switches onto the sleep mode for the sake of battery energy saving. Otherwise it would draw battery current relatively fast and would bring problems with engine start. Normal figures for the current in sleep mode are about 30 mA depending on the manufacturer. Keeping in mind this it is worthwhile to check the vehicle on the subject of parasitic draw if fast battery discharge is suspected.  

Voltage changes while the system "awake" onto the base voltage. If it is high- CAN voltage rises, if it is low-CAN voltage decreases. Check the manufacturer spec for each particular case.

Some devices such as door module control must be in standby mode all the time to provide key entry or keyless access depending on the construction. Modules talk to each other before going to sleep confirming readiness for mode change. Also modules awake each other.

The diagnostics for the CAN system bases on the principle of separating inputs, communication, and outputs. Scan tool simply simulates inputs and we control if the communication takes place and the outputs activate controlled devices. All these experiments refer to this main idea.

The last video shows how the Controller Aria Network "goes to sleep". Creative guys deactivated bonnet switch and then recorded this signal from the ABS connector while CAN was given command to sleep. This is very informative video where you can see modules talking and after the command data transferring stopped.Impressive video.

HONDA Multiplexing Board Worksheet

Starting from the wiring diagram below we can see that Door Multiplex Control Unit is connected to the Driver's Multiplex Control Unit  by brown wire between A15 and A2. Driver's Multiplex Control Unit is connected to the Passenger's Multiplex Control Unit by pink wire between B1 and B9. The earth connection is provided by black wire for Door Unit through A12 and A19, for Driver's Unit through B11 and A15, for Passenger's Unit through B22 and A8. Power supply wire has pink colour and is connected to the A1, A12, and A24 accordingly for Door Unit, Driver's Unit, and Passenger's Unit.

The video clip below shows that window on the driver side goes up but doesn't go down.

Because there is still communication between the node and actuator while we put the window up but we cannot hear clicking noise from the relay trying to put the window down I came to the preliminary conclusion that there is a fault with a signal out. We must check this signal, the relay connection, or relay itself.

Following the instruction from manufacturer we put the system into the mode1 and tried to find possible faults. However, DTC doesn't allow identifying this fault. There is no beep signal from buzzer.

In this case we cannot prove preliminary conclusion.
 So that, we come to the continuity test which result is on the photo below:

This test proved that communication line is ok as we expected.

From here we shifted to the Mode2 and captured
 this part of the experiment on this video:

Following the manual we can see that beeper sounds once what means that circuit line is ok. Step by step we clarified that we've got the input, communication but we don't have an output.
We check voltage supply for the switching relay. Pin#30 has 12 volts voltage. But nothing comes to the pin#86 from the Passenger Node.

Wiring diagram copy below shows how the door electromotor is wired into the circuit.

Once we pull the switch up we have a signal for the relay to connect the motor to the power supply on the one side. The other side of the electromotor is grounded. It rotates then. In opposite direction we don’t have a signal to the relay. Thus, one side of the electromotor is grounded but there is no voltage supply on the other side. The motor is not acting.

By going through the experiment step by step and dividing the system onto the inputs, communication, and outputs we diagnosed the fault accurately and quite quickly. It means that different procedure compared to the analogue system signal transferring diagnostics still allows working on it effectively. The important thing is to understand the structure of digital signal system transferring and follow the manufacturer manual logically.

In this particular case we could not put the system into the sleep mode and measure the time it takes and parasitic draw. In practise, the ampere should change from 70 mA to less than 10 mA.( page5 Multiplexing Control System Instruction)