The internal mode switch is a sliding contact switch connected to the valve body. Its purpose is to let the TCM know what gear you selected, based on an electrical signal that it sends. Having a P1825 DTC basically means that the IMS can’t tell what gear you selected.
How Serious is the Code?
A P1825 diagnostic trouble code is very serious, because the transmission control module will command maximum line pressure, which will damage the clutches, seals, valves and other components. The solenoids may also not function, along with the torque converter lockup clutch and the adaptive learn shifting functionalities.
Symptoms of a P1825 include:
- Very abrupt gear changes
- Transmission won’t go into the correct gear
- PRNDL display stops working
- Limited torque converter operation
- Limp Mode
- Internal mode switch failure
- Shift cable damage or it’s out of adjustment
How to Diagnose the Code?
Diagnosing a P1825 DTC involves checking the shift linkage going to the internal mode switch. If it is out of adjustment, then problems can arise. But if the internal mode switch is at fault, then electrical tests will reveal it.
What Repairs Will Fix P1825?
- Adjusting the shift cable
- Replacing the internal mode switch
P1819 – Internal Mode Switch – No Start\Wrong Range
P1820 – Internal Mode Switch Circuit A Low
P1821 – Internal Mode Switch Circuit B Low
P1822 – Internal Mode Switch Circuit B High
P1823 – Internal Mode Switch Circuit P Low
P1824 – Internal Mode Switch Circuit P High
P1826 – Internal Mode Switch Circuit C High