Honda Civic Service Manual page 269

PGM-FI System
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DTC Troubleshooting (cont'd)
DTC P0123: TP Sensor Circuit High Voltage
1 . T u r n t h e i g n i t i o n s w i t c h o N ( l l )
2. Check the throttle position with the scan tool.
ls there about 10% or 0.5 V when the throttle is
fully closed and about 90% or 4.5 V when the
throttle is f ully opened?
YES lntermittent failure. system is OK at this time.
Check for poor connections or loose terminals at
t h e T P s e n s o r a n d a t t h e E C M , I
NO Go to step 3.
3. Turn the ignition switch OFF.
4. Disconnect the TP sensor 3P connector.
5 . T u r n t h e i g n i t i o n s w i t c h O N ( l l ) .
6. At the wire harness side, measure voltage between
the TP sensor 3P connector terminals No. 1 and
N o . 3 .
TP SENSOR 3P CONNECTOR
W;re side of female terminals
ls thete about 5 V?
YES-Replace the throttle body (the TP sensor is
not available separately). I
NO Go to step 7.
11-62
7. Measure voltage between ECM connector
terminals A10 and A20.
ECM CONNECTOR A 131PI
Wire side of female terminals
Is there about 5 V?
YES- Repair open in the wire between the ECM
(A10) and the TP sensor. t
NO Update the ECM if it does not have the latest
soflware, or substitute a known-good ECM, then
recheck (see page 11-6). 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