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Home >> Chevrolet >> 1992 >> Suburban 3/4 Ton 2WD V8-350 5.7L >> Repair and Diagnosis >> Powertrain Management >> Transmission Control Systems >> Relays and Modules - Transmission and Drivetrain >> Relays and Modules - A/T >> Control Module >> Description and Operation >> Calculated Ratio
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Calculated Ratio

Undefined Ratio Circuit:





Ratio is an input calculated by the PCM/TCM from the output and input speed sensor readings.

If the PCM/TCM calculates a ratio for gears 1st, 2nd and 3rd, that is inconsistent with the gear being commanded by the PCM/TCM, and the condition lasts for over 2 seconds, Code 85 (undefined ratio) will set.

While code 85 is present, line pressure (force motor duty cycle) will be set to a default value. If the undefined ratio condition goes away, normal transmission operation will resume after the next ignition cycle.
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