Powertrain, generic (extended)

P2CD9 Turbocharger/Supercharger Boost Sensor D Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2CD9 reports a boost sensor D voltage above the highest valid level. A signal pinned near the reference rarely reflects real overboost; more often the signal wire touches 5 V or battery voltage, the sensor ground is open, or a broken signal line floats up through a pull-up inside the module. No carmaker publishes a sensor D limit. Sensor A figures give an idea of the spread: Ford's 2024 petrol summary sets the high code above 4.88 V for 5 s, Saab's GM-based 1.6 turbo above 4.8 V and the 2.0 turbo already above 3.9 V for 5 s. Because the module would otherwise read excessive pressure, it typically disables boost control on that path and falls back to wastegate base pressure. P2CD8 is the low-voltage counterpart.

Likely causes

Sensor ground open or high resistance at the connector
Signal wire shorted to 5 V reference or battery voltage
Sensor D internally failed with output stuck high

Symptoms

  • Warning lamp on
  • Engine runs on base boost only with reduced power
  • Live data shows sensor D at maximum even at idle

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–350
Time0.3–2 h

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

Parts involved

boost pressure sensor dwiring harnessecm

Related codes

P2CD6P2CD7P2CD8P25F5P0238P0242

References: law.cornell.edu, fordservicecontent.com, saabwisonline.com, saabwisonline.com.