Possible causes

– Low transmission fluid level
– Dirty transmission fluid
– Faulty Reduction solenoid valve
– Reduction solenoid valve harness is open or shorted
– Reduction solenoid valve circuit poor electrical connection

When is the code detected?

The P0770 code is detected when the ECM detects an improper voltage drop when it tries to operate the solenoid valve.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Transmission will not shift gears.

P0770 KIA Description

Reduction solenoid valve is turned ON or OFF by the Transmission Control Module (TCM) in response to signals sent from the park/neutral position (PNP) switch, vehicle speed and Engine Control Module (ECM) (throttle opening). Gears will then be shifted to the optimum position.