TM 9-2320-280-20-1REFERENCE INFORMATIONTRANSMISSION SYSTEM(4L80-E)DTC 85Undefined Ratio ErrorCircuit Description:The control module calculates ratio based on thetransmission input speed and output speed sensorreading. The control module compares the knowntransmission ratio to the calculated ratio for theparticular gear range selected.DTC 85 Will Set When:lTP is greater than 25%.. Not in park neutral, or 4th gear.. Engine speed is greater than 300 rpm.lVehicle speed is greater than 7 mph (11 kph).l All conditions are met for 2 seconds.DTC 86Low Ratio ErrorCircuit Description:The control module calculates ratio based on thetransmission input speed and output speed sensorreadings. The control module compares the knowntransmission ratio to the calculated ratio for theparticular gear range selected.DTC 86 Will Set When:llllllNot 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 orsecond gear.All conditions are met for 2 seconds.DTC 87High Ratio ErrorCircuit Description:The control module calculates ratio based on thetransmission input speed and output speed sensorreadings. The control module compares the knowntransmission ratio to the calculated ratio for theparticular gear range selected.DTC 87 Will Set When:lTP greater than 25%.lNot in park, reverse, or neutral.. Engine speed greater than 300 rpm.. Vehicle speed greater than 7 mph (11 kph).lTransmission temperature is greater than68°F (20°C).lAll conditions are met for 2 seconds.2-427
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