Internal mode switch out of adjustment or worn contacts; Damaged, corroded or loose connector at the transmission or control module; Wiring fault in the mode switch circuits (open circuit, short to earth or short to voltage); Selector cable or linkage misadjusted or worn, so the lever and switch disagree; Contamination or fluid ingress at the transmission harness connector; Faulty transmission control module.

P1825

Internal Mode Switch Illegal Range.

Saturn
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
8: AreaTransmission
25: FaultThe specific fault in that area

What it means

P1825 on a Saturn means the transmission control module has seen an illegal or impossible signal combination from the internal mode switch, also called the transmission range switch, which reports the position of the selector lever. The module expects only certain input patterns for Park, Reverse, Neutral, Drive and the lower gears, and it set the code when the pattern fell outside them. The exact switch design and wiring depend on the model and transmission, so check the model-specific information.

Symptoms

Malfunction indicator lamp or transmission warning lamp on
Gear indicator on the dash showing the wrong position or flickering
Engine will not start in Park or Neutral, or starts in other positions
Harsh, delayed or incorrect shifts
Transmission stuck in one gear (limp mode)
Reverse lamps not working or working at the wrong time

Possible causes

Internal mode switch out of adjustment or worn contactslikely
Damaged, corroded or loose connector at the transmission or control modulelikely
Wiring fault in the mode switch circuits (open circuit, short to earth or short to voltage)possible
Selector cable or linkage misadjusted or worn, so the lever and switch disagreepossible
Contamination or fluid ingress at the transmission harness connectorpossible
Faulty transmission control modulerare

How to diagnose

Read all stored codes and freeze frame data, noting the selector position and whether other transmission or starter-related codes are present
Check the transmission fluid level and condition, as the correct level is needed for reliable testing
Inspect the transmission connector and harness for corrosion, fluid, chafing and pushed-back pins
Compare the selector lever position with the gear position shown on the scan tool in each range and look for mismatches
Check the selector cable or linkage adjustment against the manufacturer's procedure for the model
Test the mode switch circuits for continuity, shorts and voltage in each selector position, using the model-specific wiring diagram
Check the mode switch reading through each range with a scan tool to find which input is incorrect
Confirm the control module's power and earths before suspecting the module itself

How to fix

Adjust the selector linkage or switch to specification
Repair or replace the damaged connector terminals and clean out any contamination
Repair the wiring fault found in the mode switch circuits
Replace the internal mode switch or the assembly it is part of if the contacts are worn or faulty
Replace or repair worn selector cable or linkage components
Replace or repair the transmission control module only after the wiring and switch are proven good

Can I keep driving?

Medium severity

The car can usually be driven carefully for a short time, but the transmission may shift badly or go into limp mode and may not start reliably. Have it checked soon, and stop driving if it will not select gears properly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.