Saab 9000 - Page 175

172 Fault diagnosis
Diagnostic trouble code P0420
Three way catalytic converter
Symptom of fault
The CHECK ENGINE lamp (MIL) is on.
Conditions
Diagnosis not yet performed this trip
Heating of the three way catalytic con-
verter:
• Vehicle speed>
O
mph(>
O
km/h)
• Open throttle
• Engine speed (rpm) x load (kPa)
=
>
60,000
•
Aggregate acceleration >
15
sec.
• Above conditions fulfilled for 120 sec.
Evaluation of the three way catalytic
converter:
• Speed 19-62mph (30-100km/h).
• Open throttle
• Engine speed (rpm) x load (kPa)
=
60,000
-
260,000
• Coolant temperature
>
60°
C (> 140° F)
• Rear heated oxygen sensor
>
0.4
V at any time in
this driving cycle.
"\\\I////
.........
/
CHECK ENGINE
0.6
/
'
////1\\\".
0.3
------------------
ov
Rear heated oxygen sensor voltage changes are
corrected in regard to engine load and rpm and total-
led in a measurement window determined by the
front heated oxygen sensor. If the total exceeds a ca-
librated value, the fault criteria are satisfied.
Diagnostic help
A temporary or permanent decrease in the capacity of
the three way catalytic converter may be caused by:
• leaded fuel or fuel with
a
sulphur content.
• fuel additives.
• additives in the motor oil if oil consumption is ab-
normal.
·
Saab 9000