TM 9-2320-280-20-1
REFERENCE INFORMATION
TRANSMISSION SYSTEM
(4L80-E)
DTC 85
Undefined Ratio Error
Circuit Description:
The control module calculates ratio based on the
transmission input speed and output speed sensor
reading. The control module compares the known
transmission ratio to the calculated ratio for the
particular gear range selected.
DTC 85 Will Set When:
l TP is greater than 25%.
. Not in park neutral, or 4th gear.
. Engine speed is greater than 300 rpm.
l Vehicle speed is greater than 7 mph (11 kph).
l All conditions are met for 2 seconds.
DTC 86
Low Ratio Error
Circuit Description:
The control module calculates ratio based on the
transmission input speed and output speed sensor
readings. The control module compares the known
transmission ratio to the calculated ratio for the
particular gear range selected.
DTC 86 Will Set When:
l
l
l
l
l
l
Not in park, reverse, or neutral.
Engine speed greater than 300 rpm.
TP greater than 25%.
Vehicle speed is greater than 7 mph (11 kph).
Trans gear ratio is less than 1.06 in first or
second gear.
All conditions are met for 2 seconds.
DTC 87
High Ratio Error
Circuit Description:
The control module calculates ratio based on the
transmission input speed and output speed sensor
readings. The control module compares the known
transmission ratio to the calculated ratio for the
particular gear range selected.
DTC 87 Will Set When:
l TP greater than 25%.
l Not in park, reverse, or neutral.
. Engine speed greater than 300 rpm.
. Vehicle speed greater than 7 mph (11 kph).
l Transmission temperature is greater than
68°F (20°C).
l All conditions are met for 2 seconds.
2-427
