Honda Civic Service Manual page 296

DTC Pl166: Ay'F Sensor (Sensor 1) Heater
Circuit Malfunction
1 . R e s e t t h e E C M ( s e e p a g e 1 1 - 4 ) .
2. Start the engine.
ls DTC P1166 indicated?
YES-Go to step 3.
NO-lntermittent failure, system is OK at this lime.
Check for poor connections or loose terminals at
the Ay'F sensor relay, the A,/F sensor (Sensor 1), and
t h e E c M . !
3. Check the following fuse:
. No. 14 OPTION (30A)fuse in under-hood fuse/
reray Dox.
. No. 2*B LAF (Ay'F) HEATER (20A) fuse in under-
dash fuse/relay box.
. No. 4 ACG (10A) in underdash fuse/relay box.
Are any of the fuses blown?
YES Repair short in the wire between the Ay'F
sensor relay and the fuses.I
NO Go to step 4.
4. Measure voltage between ECM connector
terminals A1 and A24. 30 seconds after the ignition
s w i t c h i s t u r n e d O N ( l l ) .
ECM CONNECTOR A I31P)
W i r e s r d e o f l e m a l e t e r m i n a l s
Is therc battery voltage?
YES-Update the ECM if it does not have the latest
soflware, 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-Go to step 5.
5. Measure voltage between ECM connector
terminals A22 and A24.
ECM CONNECTOR A {31P}
Wire side of female terminals
ls there battery voltage?
YES Go to step 6.
N O - G o t o s t e p 1 0 .
6. Turn the ignition switch OFF.
7. Disconnect ECM connector E (31P).
8 . 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 ) .
( c o n t ' d )
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