Self-Diagnosis

Self-diagnosis: the board computer checks itself and a part of its periphery and stores faults in the program
memory that last longer than approx. S seconds.

After faults are stored, an "F" (fault flag) appears in the upper left corner of the lime display. In addition,
the board computer functions affected by the faults are blocked by a flashing "F" in the function display.

If the fault is no longer present after an interval of approx. 8 seconds, the fault flag is erased and the
affected board computer functions are released again.: The trouble code remains stored in the program I
memory, however. The display of a trouble code without an active fault I flag indicates the presence of a loose
contact.

The stored trouble codes can be read out by means of TECH 1 or Diagnostic Switch KM-640 (see section
5.4.1 or section 5.6.4).

Range Calibration

Fit paperclip to Diagnostic plug A-D
Fit 120 Ohm resistor in place of tank sensor.

Remove Plug arrowed right, and connect resistor to plug.

Adjust diagnostic mode 5 by repeatedly actuating the stepping
key.

The clock display shows d: 5

The function display remains blank.

Change is made to the actual calibration mode by pressing the
minutes hole contact.

The clock display shows "A".

The function selection display flashes the range arrow.

The function display shows "12L" (calibration with defined petrol
quantity). This calibration mode is used only in the factory.

A switchover is made to the calibration mode with substitutional
resistance by pressing the stepping key.

The function display shows the value of substitutional resistance.

The calibration process is initiated after the start key

is actuated> 3 sec; the function display shows "----" until storage
is ended.

After approx. 5 sec, the function display shows the range
corresponding to the substitutional resistance (approx. 120 km or
75 m).

[83 miles on my V6]

The calibration mode is exited by disconnecting the diagnostic
switch.

If during calibration the board computer recognises a faulty
signal level, an "H" (voltage too high) or "L" (voltage too low)
flashes for 5 sec instead of the range being displayed. The board
computer then returns to diagnostic mode 5.

In this case, resistor is fitted.

After a successful recalibration, the following measures are to be
carried out:

- Remove resistor, connect tank gauge (ignition OFF!)

Erase trouble code memory (see section 6.3.2)

- Select board computer range function and press start key. The
function display shows the range calculated from the current tank
content.

Range Correction

Fit paperclip to Diagnostic plug A-D

Adjust diagnostic mode 5 by repeatedly pressing the stepping key.

The Clock display shows d : 5

The function display remains blank

Change is made to the actual correction mode by pressing the hours hole
contact.

The clock display shows A : xx; at the same time, the currently stored
correction appears at the positions designated by xx. The correction value is
displayed without a decimal point, e.g. 6 for 0.6 gallon

The function display flashes the range arrow.

Press the Stepping key.

The function display shows the range based on the current tank content, a
standard consumption of 28.3 mpg and the currently adjusted correction.

The stepping key can be used to adjust the desired correction in the clock
display in the continuous mode. Simultaneously, the displayed range
changes by approximately 3 miles with each key press.

If the right correction value has been set, the correction value is
permanently stored in the program memory by actuating the start key > 1
second; the function display shows ---- until storage is complete.

The correction mode is exited by disconnecting he diagnostic switch.

Now select board computer range function and press the start key. The
function display shows the range calculated from the current tank content.

Diagnostic Mode d:1

Fit paperclip to Diagnostic plug A-D

The clock display shows designation "d:1".
The function display introduces the trouble code
read-out by flashing the number "12" three times
and then flashing the trouble codes three times in
numerical order.

The entire trouble code set is repeatedly given until diagnostic mode 1 is
exited.

If no fault is present,"- - - -" is flashed instead of the trouble code.

After removal of cause of fault, the fault memory can be erased by actuating
the start key.

Trouble
Code

Trouble Code Explanation

Trouble-shooting

167

The trouble code is set when the
the fuel gauge signal voltage at
the board computer is too small.
Simultaneously, the range function
is blocked by a flashing "F".

- Tank indicator in instrument does not function:
1. Fuel gauge or connection defective (short circuit
to ground)
2. Instrument defective

-Tank indicator in instrument functions:
1. Lead interruption between fuel gauge and board
computer Ter. 26,
bimetal measuring device or Ter. 8, on
VECTRA/CAVALIER with LCD instrument
2. Wrong program memory installed
3. Board computer defective

168

The trouble code is set when the
the fuel gauge signal voltage at
the board computer is too large.
Simultaneously, the range function
is blocked by a flashing "F".

- Tank indicator in instrument does not function:
1. Fuel gauge or connection defective (interruption)
2. Ground connection at fuel gauge defective
3. Instrument defective

- Tank indicator in instrument functions:
1. Wrong program memory installed
2. Board computer defective

169

The trouble code is set when the
temperature sensor signal voltage at
the board computer is too low.
Simultaneously, the outside
temperature function is blocked by a
flashing "F".

1. Disconnect temperature sensor plug connection
P13 and measure
resistance of temperature sensor (multimeter,
measuring range: 2
Nominal value: 700 - 135 k .
2. Short circuit to ground of lead between board
computer Ter. 13 and
temperature sensor plug P13
3. Board computer defective

171

The trouble code is set when the
temperature sensor signal voltage at
the board computer is too high.
Simultaneously, the outside
temperature function is blocked by a
flashing "F".

1 .Disconnect temperature sensor plug connection
P13 and measure
resistance of temperature sensor (multimeter,
measuring range: 2
Nominal value: 700 - 135 k .
2.Lead interruption between board computer Ter. 13
and temperature sensor plug P13
3.Lead interruption between board computer Ter. 12
and temperature sensor plug P13
4.Board computer defective

173

The trouble code is set when the
injection control unit signal shows
a ground level longer than 500 ms;
The following functions are blocked
by a flashing "F".
- current consumption
- average consumption
- range

1. Short circuit to ground of lead between board
computer Ter. 24 and
control unit of injection system
2.Board computer defective
3.Control unit of injection system defective