P1840

Internal Mode Switch 'S' Circuit Low Voltage

Severity

⚠️ Medium

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$17–56 (est.)

Symptoms

Incorrect display of the current transmission mode
Gear shifting problems
Check engine light comes on
The gearbox may go into emergency mode
Difficulty starting the engine in some modes

Causes

Malfunction of the internal mode switch
Open or short circuit in switch circuit
Poor contact in connectors
Problems with the transmission control unit
Switch contact corrosion

How to Fix

Check the integrity of the mode switch circuit
Inspect and clean switch contacts
Check voltage at switch
If necessary, replace the mode switch
Check and reflash the transmission control unit

Related codes

P1839 P1841 P0705