Powertrain, generic · Transmission

P0816 Downshift Switch Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Tap-up and tap-down switches let the driver choose gears on an automatic (selector gate, buttons or paddles). GM, Ford and Saab all treat a shift request that appears where it is impossible – in park or neutral, at Ford also reverse – or that stays on implausibly long as a stuck switch. P0816 is the mirror of P0815 for the downshift switch. GM's 2025 table sets it when 'tap down' stays on for more than 1 s (100 ms raster, over 9 V), the 2018 hybrid table after 2 s in P/N or 655 s in drive, type C without MIL; Saab's 9-4X after 1 s in P/N or 10 minutes in a drive range; Ford's SelectShift when the switch is closed in P, R or N, without MIL. On selectors with a resistor network a short to positive in the downshift branch sets P0816. Manual shifting is disabled, automatic operation stays normal.

Likely causes

Downshift switch or paddle sticking or faulty
Signal wire shorted to positive
Selector assembly faulty
Body or transmission module

Symptoms

  • Manual down shifting not working
  • Transmission stays in the normal automatic mode
  • No check engine lamp

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–600
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

tap shift switchgear selectorswitch wiringtransmission control module

Related codes

P0815P0826P0827P0828P0819

References: gsi.ext.gm.com, gsi.ext.gm.com, saabwisonline.com, newtonnet.co.uk.