What does it mean?
P1709 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: A/T Transmission Gear Switch Circuit Malfunction .
Symptoms
- MIL on with a transmission warning
- Gear indicator in the cluster wrong, blank or flashing
- Transmission engaging the wrong gear or defaulting to a fixed one
- Harsh engagement when moving into drive or reverse
- Engine cranking in gear, or refusing to crank in park
- Fault coming and going when the lever is nudged
Likely causes
- Gear switch contacts worn or contaminated, producing an invalid gear code
- Open or shorted wiring between the gear switch and the transmission module
- Corroded connector at the switch, which is exposed to underbody water spray
- Switch adjustment drifted so its positions no longer line up with the lever detents
- Broken or stretched selector cable
- Poor supply or ground to the switch
- Transmission module input circuit fault
How to fix it
- Monitor the gear switch inputs in live data through every selector position
- Compare the readings against the valid position table for that transmission
- Check selector cable adjustment and the detent feel at the lever
- Inspect the switch connector for corrosion and water, then clean and reseat it
- Measure switch continuity in each position directly at its connector
- Test the wiring between the switch and the module for open and short conditions
- Replace the gear switch if any position reads incorrectly, and repair the harness where it is damaged