EDU 3 Trip Computer and Clock

EDU 3 Trip Computer And Clock: Cars With A Manual Gearbox:

EDU 3 Trip Computer And Clock: Cars With Automatic Transmission:

General
The EDU 3 trip computer (Electronic Display Unit) is available in two basic versions, one for a manual gearbox and one for automatic transmission. The computer is programmable, which means that a replacement trip computer must be programmed for the car model, etc. in which it is fitted.

Programming is performed with the ISAT scan tool. In addition, the ISAT scan tool can be used to carry out certain adjustments and tests and to obtain readouts of diagnostic trouble codes.

The trip computer provides the following information:

In The Left-hand Part Of The Display
^ Current and average fuel consumption.
^ Range on remaining fuel.
^ Battery voltage.
^ Outside temperature.

In The Right-hand Part Of The Display
^ Selector lever position (on cars with automatic transmission).
^ Current fuel consumption (horizontal scale).
^ Warning message CHECK ENGINE (malfunction indicator lamp) in the event of a malfunction in the Trionic or Motronic engine management systems or in the ETS electronically controlled throttle.
^ Warning message CHECK RADIATOR LEVEL if the coolant level is too low.

When the ignition is switched on, all check indicator lamps should light up and then go out one by one within 4 seconds.

Use the R and INFO buttons to select the different functions of the trip computer and the display in km or miles, for instance. The buttons are situated on clock 49 or SCC trip computer 241.

^ Trip computer 210 is supplied with current continuously via fuse 17 and also via fuse 13 when the ignition switch is in the Drive position.

^ The brightness of the display is automatically adjusted in daylight by means of a sensor on either the SCC unit or the clock. When driving in the dark, display brightness can be adjusted with rheostat 16 (lighting for controls).

Fuel Consumption
In order to calculate and present current and average fuel consumption, the trip computer requires data on:
^ the distance driven from vehicle speed sensor 132 via pin 9.
^ current fuel consumption from the engine control module via pin 8. The control module uses the control pulses to the injectors, the frequency of which corresponds to the current fuel consumption.

Range On Remaining Fuel.
To show the range (the distance that can be driven with the fuel remaining in the tank), fuel level sensor 46 is connected to the trip computer via pin 33. The trip computer calculates the range from the average fuel consumption over the last 20 minutes.

Quantity Of Fuel
The trip computer supplies about 12 V to the fuel gauge via pin 22. From pin 24 the trip computer supplies a 1-9 V signal which controls the reading shown on fuel gauge 47A.

1 V = tank empty, 9 V = tank full. When about 10 liters of fuel remains in the tank the trip computer grounds, via pin 25, the indicator lamp (low fuel warning 47B), which then lights up.

Engine Coolant Temperature
The trip computer supplies about 12 V to the coolant temperature gauge via pin 22. From pin 24 the trip computer supplies a 1-9 V signal which controls the reading shown on coolant temperature gauge 47C.

1 V = minimum temperature, 9 V = maximum temperature.

Outside Temperature
Information about the current outside temperature is obtained from outside temperature sensor 286 via pin 35. The sensor is located behind the car's front spoiler.

After processing, the current outside temperature value is sent to the ACC control module via pin 23. The signal is a pulse train.

The ice warning function is automatically activated and displays the outside temperature as soon as the temperature comes within the range of -3°C to +3°C. The temperature is then shown on the display until another function is selected with the INFO button or until the outside temperature leaves the range -6°C to +6°C, that is to say the function has a certain hysteresis (delay).

Low Coolant Level
The warning signal for low coolant level is received from sensor 242 via pin 17. The sensor closes when the level is too low

Radiator Fan Control
The radiator fans are controlled via the trip computer. By grounding relay 155 via pin 5, the fan starts at low speed (2-speed fan 366) or in the case of fan 37, at normal speed. Relay 81 is grounded via pin 6, which activates the high speed mode on the 2-speed fan.

After-running of the fans is also controlled by the trip computer. When the ignition switch is turned to the OFF position, the trip computer checks the temperature of the coolant. If it is too high, the trip computer allows after-running for a maximum of 3.5 minutes.

A/C Control
When the A/C system is to be engaged, a 12 V signal is received via pin 10 from ACC control module 216 or from A/C switch 169. The trip computer checks the temperature of the coolant and if it is not too high, sends a 12 V signal via pin 4 to pressure switch 166.

CHECK ENGINE
The malfunction indicator (CHECK ENGINE) lamp in the trip computer lights up if there is a fault in the Trionic or Motronic systems. The data is received via pin 12.

Gear Position Indication
In cars with automatic
transmission, the trip computer is connected to transmission range switch 245 via pins 18,19 and 20.

Signals From The Clock/SCC
The following information comes from the clock or the SCC:
^ INFO button via pin 14.
^ R button via pin 15.
^ Light sensor signal via pin 36.

Backlighting
Lighting of the display is controlled by rheostat 16 and also by the value of the light sensor.