P1820 – Internal Mode Switch Circuit ‘A’ Low

P1820 Possible Symptoms

Engine Light ON (or Service Engine Soon Warning Light)

P1820 Possible Causes

Faulty Internal Mode Switch,Internal Mode Switch harness is open or shorted,Internal Mode Switch circuit poor electrical connection

P1820 Description

With the engine runtime over 5 seconds, system voltage from 8-18v, Fuel Cutoff inactive, engine torque from 30-148 ft-lb (40-200 Nm), the Powertrain Control Module (PCM) detects that the Internal Mode Switch (IMS) signal indicated PARK for 2 seconds and then the IMS indicated a transitional state between D4 and D3, conditions met for 5 seconds.