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P040D Powertrain

EGR Temperature Sensor A Circuit High

EGR temperature sensor A above upper plausibility — open signal or short to B+. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.

Affected components

  • Egr temperature sensor

Common causes

  • High likelihood: Open signal line
  • Low likelihood: Connector pins corroded - high contact resistance
  • Low likelihood: Supply wire pinched against B+ source

Possible symptoms

  • Check engine light on
  • Pinging or knocking under load
  • Power loss and hesitation
  • Possible rough idle
  • Failed emissions inspection (NOx)

Diagnostic notes

  • The malfunction indicator lamp may illuminate
  • This code can affect emissions

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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