128 Fault diagnosis
Diagnostic trouble codes P0136, P0138, P0140
Rear heated oxygen sensor (oxygen sensor 2)
Symptom of fault
The CHECK ENGINE lamp (MIL) is on.
Conditions
P0136: All-embracingDTC.
P0138:
Ignition
switch in ON position.
sensor voltage
>
1500
mV for more than 5 sec.
P0140: Diagnosis not yet performed this trip.
Car in motion.
Coolant temperature
>
70° C (>
.158° F).
The
oxygen sensor's voltage has not climbed above
0.4 V nor changed by more than 0.5 V in 500 se-
conds.
µp
µp
H70-1
47
70 67
51
Diagnostic help
Operation of the oxygen sensor can be ascertained
using an ISAT scan tool.
- Select "READ FUNCTIONS".
- Select "O2S 2".
At full load the ISAT scan tool should show a reading
of >0.7V.
Atfuel shut-of the ISAT scan tool should show area-
ding of about
O
V.
_
If the reference ground or sensor voltage of any of
the oxygen sensors is short-circuitedto battery posi-
tive (B+) in the wiring harness or in any of the oxygen
sensors, DTCs P0132 and P0138 will probably both
be generated.
The control module inputs of the oxygen sensors are
high-ohmic. If moisture gets into the connectors of
some of the oxygen sensors, a diagnostic troubte co-
de will
be
generated.
Saab9000
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