Vehicles that have been manually shiftable automatic transmission automated manual transmission, use something called a downshift switch telling the ECU when you have used the gear lever paddle shifters to request a downshift. If there is a problem with the downshift switch, a P0816 DTC will be saved.
How Serious is the Code?
Transmission problems resulting from a P0816 diagnostic trouble code are not likely to leave you stranded, but it might get stuck in limp mode, which would leave you restricted to a single forward gear.
Symptoms of a P0816 include:
- Manual shifting function disabled
- Limp Mode
- Warning lights
- Damaged wiring/connectors
- Failed transmission gear selection switch
- Failed downshift solenoid
- Failed Normal/Performance switch
How to Diagnose the Code?
Often times, the cause of a P0816 OBDII trouble code is an electrical short. So a mechanic should start by inspecting the wiring and connectors, and then test the downshift switch itself.
What Repairs Will Fix P0816?
- Repair damaged wiring/connectors
- Replace transmission gear selection switch
- Replace downshift solenoid
- Replace Normal/Performance switch