Error code

OBD2 P0791

OBD2P0791
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Intermediate Shaft Speed Sensor 'A' Circuit.

Severity

moderateCan be driven, but performance may suffer and fuel economy will likely decrease.

Summary

P0791 indicates an issue with the intermediate shaft speed sensor circuit in the transmission, which can affect shift strategy and overall performance.

Symptoms

  • Malfunction Indicator Lamp (MIL) lights up
  • Harsh or failed shifts
  • Decreased fuel economy
  • Speedometer issues
  • Engine stalling, misfiring, hesitation

Common Causes

  • Defective intermediate shaft speed sensor
  • Wiring issues or poor connections in the circuit
  • Contaminated transmission fluid
  • Faulty shift solenoid
  • PCM (Powertrain Control Module) malfunction

Diagnosis

  1. Inspect the intermediate shaft speed sensor for damage or wear
  2. Check wiring connections and circuits for corrosion or breaks
  3. Test transmission fluid quality and replace if necessary

Fixes

  • Replace faulty intermediate shaft speed sensor

FAQ

What should I do if my car's MIL lights up with P0791?

Inspect the intermediate shaft speed sensor and wiring for issues. If problems are found, replace them to restore proper transmission function.

Can a faulty PCM cause this code?

Yes, a malfunctioning Powertrain Control Module (PCM) can trigger P0791 due to incorrect signal processing.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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