2015 Mazda5 issue?

[(Bean)]

The weird issue...about a year ago 30 min into a highway drive the D (Drive) light indicator on the dash between the RPM and speedometer flashed. It was quick - wasn't even sure it happened, but in the time since then it has happened a lot at both highway and city speeds and sometimes it stays off for 5 seconds or so. Some drives it doesn't happen at all - sometimes it is a lot - sometimes it is a few times at the start and doesn't happen again even for a long 5 hours drive. T There has never been any warning lights - AT or Engine. The speed remains constant highway or town streets. The cruise control works and doesn't hick up when it happens.

Thanks

 

[topFC3Sman]

I don't have an automatic, but I would suspect an issue with the switch on the shifter that is sporadically acting up. If the computer thinks that the car is shifted from drive to neutral, it will open up the torque converter clutch and possibly close the idle valve (if its open when driving, which it probably isnt), which will cause the engine to speed up if you're driving on the highway with no real change in vehicle speed - it'll just be slipping the torque convertor instead of having it locked. Similarly, sitting still in park, if the switch is intermittently failing and sends a sporadic signal to the computer saying that you've left park, it'll probably try to bump up the idle speed, expecting to need that extra torque reserve for the drag of the torque converter when shifting into reverse (even if the trans doesn't actually shift since reverse isn't selected by the cable) That'll make the RPM bounce around too since the more open idle valve will increase engine speed if there isn't the expected load.

The dash light flickering or going off and on does seem to back up this hypothesis as well, since that's also signaled by the shifter switch.