Honda Civic Service Manual page 544

Emission Control System
Evaporative Emission (EVAP) Gontrols (cont'd)
'99 - 0O
models only:
The scan tool indicates Diagnostic Trouble Code (DTC) P0451: The Fuel Tank Pressure sensor circuit range/
oerformance Droblem.
ECM/PCM CONNECTORS
wire side ot femare terminars sG2 IGRN/BLK)
FUEL TANK
PRESSURE
SENSOR
VACUUM
PUMP/GAUGE,0 - 30 in.Hg
FUEL TANK
PRESSURE SENSOR
ASSEMBLY
EVAP TWO
WAY VALVE
I J
t l '
Ths MIL has been reDortgd on.
DTC m/$1 i3 stored.
Check the tuel tank pros3ure ser|-
sor:
1. Do the ECM/PCM Reset Proce-
dure.
2. Remove the tuellill cap.
3. Turn the ignition switch ON (ll).
4. N4onitor the FTP Sensor volt-
a g e w i t h t h e H o n d a P G M
T e s t e r , o r m e a s u r e v o l t a g e
b e t w e e n b o d y g r o u n d a n d
ECN4/PCM connector terminals
A29 and C18.
ls there approx. 2.5 V7
Check tho tuel tank pressure !on-
soa:
1 . R e m o v e t h e f u e l t a n k ( s e e
page 11 2421.
2 . R e m o v e t h e f u e l t a n k p r e s -
s u r e s e n s o r a s s e m b l y f r o m
the fueltank.
3. Connect the fuel tank Pressure
S e n s o r s u b - h a r n e s s 6 P c o n -
n e c t o r t o t h e a c c e s s p a n e l
side connector,
4. Disconnect the hose between
the EVAP two way valvg and
the fuel tank pressure sensor at
the EVAP two way valve end.
5 . C o n n e c t a v a c u u m p u m p t o
the open end ofthat hose.
6. Turn the ignition switch ON (ll).
7. Monitor the FTP Sensor volt,
a g e w i t h t h e H o n d a P G M
T e s t e r , o r m e a s u r e v o l t a g e
between ECM/PCM connector
t e r m i n a l s A 2 9 a n d C 1 8 , a n d
carefully pump vacuum on the
hose one stroke at a time.
8. The voltage sho!ld smoothly
drop from the stading approx.
2.5 V down to approx. '1.5 V.
STOP applying vacuum when
the voltage drops to approx. 1.5
V or damage to the fuel tank
pressure sensor may occur.
Does the voltage drop to
approx. 1.5 V and hold?
Sub3titute a known-good ECM/
PCM and r6check. It symptom/
indicltion 90e3 aw.y, replac\. th€
original ECM/PCM.
A (32P)
A973X - 041 -
xxxxx
11- 2 7 4