P023D: Manifold Absolute Pressure - Turbocharger/Supercharger Boost Sensor A Correlation

What does P023D mean?

P023D compares the manifold pressure sensor (after the throttle) with boost sensor A (before the throttle): with the engine stopped both must read the same ambient pressure. Saab's 2.8 V6 checks this once per trip with the ignition on before starting and sets the code at a difference of more than 12 kPa, with the warning light and limp mode limited to 170 Nm. The code does not say which sensor is wrong – barometric pressure as a third value decides. Electrical faults of either sensor (P0107/P0108, P0237/P0238) block the test and must be fixed first. GM and Ford run the same comparison but report it as P0236, P0106 or P2227.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Limp mode, limited power
• Otherwise often unremarkable

Common causes

• High Manifold or boost sensor drifting or dirty
• Medium Contact resistance at connector or ground of one sensor
• Medium Pressure port or hose of one sensor blocked (oil sludge, ice)
• Low Engine module or reference voltage

Likelihood is a general estimate across vehicles; your make and model may differ.