What does it mean?
DTC P0790 sets when the PCM/TCM has detected a malfunction in the electrical circuit of the transmission mode selector. The switch, system wiring and connectors, and mode actuator are all included in this circuit. The transmission range (TR) switch or mode selector, also called the manual lever position (MLP) sensor, is used as an input to the PCM/TCM, which indicates the drive range requested by the driver.
The transmission range switch is usually located on the outside of the case on the transmission/transaxle housing and attached to the shifter. As the gear range selector is moved, TR switch can make a variety of switch connections for each gear range. These inputs allow the TCM to determine which gear range has been selected.
The switch is used by the TCM to Keep the engine from starting in any gear position except park or neutral Allow a progressive 1–2–3–4 shift sequence in drive Limit upshifts in manual ranges Operate the backup lights in reverse NOTE: Whenever diagnosing a 700 series DTC (Diagnostic Trouble Code) with a transmission, transfer case or other driveline components, check for a DTC under chassis and body systems, not just under “P” or powertrain/engine or emission control type codes.
Module communications DTCs are “U” codes. These are most often found when looking for DTCs under chassis or body systems. Chassis related codes are labeled “C” and body system related codes are labeled “B” codes and these can cause drivetrain issues if they affect a sensor that is also used by the heating and air conditioning system.