Powertrain, generic (extended)

P2399 Diesel Intake Air Flow B Position Sensor Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2399 is the upper-limit counterpart of P2398: the B-throttle position signal reads higher than any real flap angle can produce. That usually points to a lost sensor ground, a signal wire touching the 5 V reference or battery voltage, or water bridging the terminals in the connector. No manufacturer is known to publish P2399. For the A valve the LML Duramax from GM uses P02E9 once the voltage exceeds 4.72 V during 5 s; Ford's 2023 diesels react when 4.92 V is passed for 3 s. Measure the ground lead back to the module first, since a weak ground lifts the signal without the sensor itself being damaged. The consequences resemble those of the other sensor codes: flap de-energised, MIL, EGR and regeneration compromised.

Likely causes

Open or high-resistance sensor ground
Signal wire shorted to 5 V reference or battery voltage
Moisture bridging terminals in the connector
Failed position sensor

Symptoms

  • MIL on
  • Flap stays at spring position
  • Regeneration suspended

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–500
Time0.5–2 h

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

Parts involved

diesel intake throttle position sensordiesel intake throttle valvesensor wiring

Related codes

P2398P2396P2397P239AP02E9

References: law.cornell.edu, gsi.ext.gm.com, fordservicecontent.com.