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P27A4 Powertrain

Electric/Auxiliary Transmission Fluid Pump B Control Circuit Low

Voltage on the second auxiliary transmission fluid pump control line is below the expected window. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.

Affected components

  • Aux trans pump b
  • Wiring harness

Common causes

  • High likelihood: Control wire shorted to ground
  • Medium likelihood: Motor winding short
  • Low likelihood: Connector pins corroded - high contact resistance

Possible symptoms

  • Check engine or transmission warning light on
  • Harsh, delayed, or missing shifts
  • Possible limp mode (locked in one gear)
  • Slipping or shuddering during gear changes

Diagnostic notes

  • The malfunction indicator lamp may illuminate

Related codes

Sources

Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.

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