Honda Civic Service Manual page 378

DTC Troubleshooting
DTC P0451: FTP Sensor Range/Performa nce
Problem
Special Tools Required
Vacuum Pump/Gauge, 0-30 in. Hg A973X-041-XXXXX
1 . R e m o v e t h e f u e l f i l l c a p .
2. Turn the ignition switch ON (ll)
3. l\4onitor fuel tank pressure (FTP) sensorvoltage
with the Honda PGM Tester, or medsure voltage
between ECM connectorterminals E4 and E14.
ECM CONNECTOR E 131P)
W i r e s i d e o f f e m a l e t e r m i n a l s
ls there about 2.5V?
YES-Go to step 4.
NO Replace the FTP sensor.I
Turn the ignition switch OFF.
Disconnect the hose between the EVAP two way
valve and the FTP sensor at the EVAP two way
valve end.
4 .
5 .
7 .
8 .
6. Connect a vacuum pump to the open end of the
hose.
Turn the ignition switch ON {ll).
l\4onitor FTP sensor voltage with the Honds PGM
Tester, or measure voltage between ECM
c o n n e c t o r t e r m i n a l s E 4 a n d E 1 4 , a n d c a r e f u l l y
s q u e e z e t h e v a c u u m p u m p a l i t t l e .
ECM CONNECTOR E 13lPI
Wire side of lemale terminals
The voltage should smoothly drop from about 2.5 V
t o a b o u t 1 . 5 V . S t o p a p p l y i n g v a c u u m w h e n t h e
voltage drops to about 1.5 V or damage to the FTP
sensor may occur.
Does the voltage drop to about 1.5 V and hold?
YES Check for misrouted, leaking, or broken FTP
s e n s o r v a c u u m l i n e s . l f t h e v a c u u m l i n e s a r e O K ,
update the ECM if it does not have the latest
software. or substitute a known-good ECM, then
recheck (see page 1 1-6). lf the symptom/indication
goes away with a known-good ECM, replace the
o r i g i n a l E C M . I
NO Replace the FTP sensor. !
9 .
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