AVL DiGas 4000 - Page 119

4000 4-/5-Gas Measuring Instruments Unit
Service Manual 5-23
Primary error symptom Primary cause
(of error)
Secondary cause of
error
Possible tests/
establishing cause
Remedy
Plug and/or cable
faulty or
disconnected
Not connected or
irreparably
damaged when O
2
sensor replaced
Check:
service mode and
on O
2
sensor,
DSM=07 after
zeroing?
O2=0: no signal
Connect or replace
cable
Cable to measuring
instruments unit
disconnected
Measuring
instruments unit
cable disconnected
when O
2
sensor
replaced
When cable
connected and OK:
approx. 40 k
Ω
internal resistance
should be
measurable
Connect or replace
cable
O
2
sensor faulty Condensate in
sensor due to
operation at below
5° C
Storage or operation
at temperatures
above 50° C
Stored at below 0° C
for a long period
(i.e. days)
Sensor voltage
lower than 5 mV
Ambient tempera-
ture fluctuating too
much
Condensate in hose?
Ambient/operating
conditions?
Sensor is too old:
sensor voltage must
be between 5 and
14 mV (see raw
values)
Replace sensor,
ensure required
operating conditions
Leak in exhaust
pipe
(Applies to 4-stroke
engines only and
lambda setpoint
value
≤ 1)
CO + CO
2
measurement value
less than 15 % by
volume?
O
2
> 0 %
Repair leak in
exhaust
Leak in instrument (Applies to 4-stroke
engines only and
lambda setpoint
value
≤ 1)
CO + CO
2
measurement value
less than 15 % by
volume?
O
2
> 0 %, carry out
leak test
Find leak and repair
Hose disconnected
after O2 sensor
Possible leak
between measuring
instruments unit
and O
2
sensor
At least 10 cm hose
is necessary after O
2
sensor (465)
Connect hose to
outlet or repair leak
Software
interference due to
EMC
Saved starting value
has been deleted
Service mode: when
setpoint 7 to 14 mV
in air, sensor OK
Initialise sensor again
in service mode
Oxygen measurement
value incorrect and O
2
sensor faulty
Measuring
instruments unit
faulty
Service mode: ES,
SZ not zero?
Replace measuring
instruments unit