Honda Civic Service Manual page 411

Primary Heated Oxygen Sensor (Primary- Fjq?S) (Sensor 1l
('99 - 0b Models exiept D16Y5 engine with M/T)
T h e H e a t e d o x y g e n s e n s o r s ( H o 2 S ) d e t e c t t h e o x y g e n c o n t e n t i n t h e e x h a u s t g a s a n d s i g n a | s t h e E c M / P c M ' | n o p e r a t i
the EcM/pcM receives the signars from the sensor and
varies the duration during which fuel is injected. To stabilize the
s e n s o r , s o u t p u t , t h e s e n s o r n a s a n i n t e r n a I h e a t e r . T h e P r i m a r y H o 2 S ( s e n s o r l ) i s i n s t a | l e d i n e x h a u s t m a n i f o
81642 engine: exhaust PiPe A)
SENSOR
TERMINALS
VOLTAG€ (VI
HEATER
TERMINALS
The scan tool indicates Diagnostic Trouble Code
(DTC) P0131: A low voltage
Oxygen Sensor (HO2S) (Sensor 1) circuit
RICH+ AIR-
- LEAN
FUEL
RATIO
problem in the Primary Heated
HEATER
- The MIL has been t€Ported on.
-
DTC P013'l is stored.
Problem veritication:
1. Do the ECM/PCM Reset Pro-
2 . S t a r t t h e e n g i n e . H o l d t h e
engine at 3,000 rpm wrth no
load (in Park or neutral) until
the radiator fan comes on
3 . C h e c k t h e P r i m a r Y H O 2 S
lSensor 1) output voltage wath
the scan tool during accelera
tion using wide open throttle
lntermittont f.ilure, 3ystem i3 OK
at thi3 time. Check tor Poor con'
nections or loose wires el C123
{Primary HO2S, Sensor 1) and
ECM/PCM.
Does the voltage stay at 0 5 v
or less?
C h e c k t h e f u e l p r e s s L l r e ( s e e P a g e
1 1 , 1 0 9 ) .
( T o p a g e 1 1 1 4 2 )
(cont'd)
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