I have a 1991 Itasca Suncruiser Class A motorhome with a Chevy 454 driveline (4 speed automatic transmission). No one can seem to find the diagnostic hookup on it to read any maintenance codes. The transmission is currently locked in 2nd gear. Any ideas?
That is a OBD-1 system, first gen. it does not control the transmission, only torque converter lock up. It uses the 4L80EHD transmisson not to be mistaken for the 4L80-E.
There was a recall notice for that tranmission problem sent out Jan. 31, 1994. They also extended the warranty from 36mo/50,000 mi to 60mo/75,000mi. The recall repair had to be preformed by 12/31/1994.
The diagnostic connector that you are looking for is normally located in one of two places.
First place to look; remove the dog house look around the rear engine area up on the floor board (under side of floor) tied back to other wire harness.
Second place they liked to put it; open the grill on the drivers side there is a metal panel cover about 10" X 12" , remove the cover panel and look inside, see if it's tied back with other wire harness.