Without Scan Tool
A/T DIAGNOSTIC TROUBLE CODE DIAGNOSISCHECK "N" RANGE LIGHT
The "N" range light flashes once per second if there is an abnormality in any of the items in the table which are related to the A/T system. Check for diagnostic trouble codes if the "N" range light is flashing once per second.
"N" range light flashing items
CAUTION: If the "N" range light is flashing twice per second, it means that the A/T fluid temperature is too high. Stop the vehicle in a safe place and wait until the "N" range light switches off.