When the powertrain control module (PCM) senses an abnormality in the input or output systems, the D indicator in the gauge assembly will usually blink.
When the data link connector (DLC) (located under the steering column lower cover) is connected to the Scan Tool or Honda diagnostic system (HDS), it will indicate the diagnostic trouble code (DTC) when the ignition switch is turned ON (II).
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There are 3 codes that cause a blinking D light with no Check Engine Light:
P0710 ATF temperature sensor (This code is caused by an electrical circuit problem and cannot be caused by a mechanical problem in the transmission.)
P0845 3rd clutch transmission fluid pressure switch
P1740 4th clutch transmission fluid pressure switch