Powertrain, generic · Computer and auxiliary outputs

P0608 Control Module VSS Output A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Many engine or powertrain modules turn the raw wheel or output-shaft speed into a cleaned-up vehicle speed signal and pass it on through their own driver – a square-wave signal whose frequency rises with speed – to the instrument cluster, cruise control, radio or steering. P0608 concerns output A: the module compares the commanded driver state with the actual line state and reports a short to ground or voltage, an open circuit or an internal driver fault, as CARB requires for output components. Output A is the first such output, usually the speedometer feed. If the speed sensor itself fails, P0500–P0503 set instead. No manufacturer table available to us gives thresholds; GM lists the code in older vehicles. On modern cars speed is shared over CAN, so the code mainly affects older vehicles with a hard-wired speedometer signal.

Likely causes

Short or open in the output line A to the receiving module
Corroded or spread connector pins at the module or receiver
Faulty receiving module pulling the line to ground
Internal driver fault in the module

Symptoms

  • Speedometer dead or jumping
  • Cruise control not working
  • Odometer stops counting
  • Speed-dependent functions (steering, radio volume) disturbed

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–600
Time1–3 h

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

Parts involved

engine control modulevehicle speed output wiringinstrument cluster

Related codes

P0609P0500P0501P0502P0503

References: law.cornell.edu, static.nhtsa.gov.