P234B Cylinder 9 Pressure Sensor Circuit High

P234B is stored when the cylinder 9 combustion pressure sensor signal sits above its upper limit. Nobody documents this cylinder-9 code openly, so the description borrows from the Saab 9-5 diesel (GM 2.0 CDTI): its high codes for cylinders 1–4 (P0398 for cylinder 1) need more than 2 s above threshold with the engine running, are tested once per operating cycle and are Type B. The live value then jumps to 10,000 kPa, beyond the normal span of up to 9,000 kPa. A signal pulled up usually means an open signal or ground wire – the input floats high – or a short to voltage on the reference or signal; Saab rates an unplugged connector as the most common finding. CARB demands such out-of-range checks for every input sensor. Like P234A, the code costs combustion control for the cylinder, rarely drivability.

Likely causes

Symptoms

• Check engine light after two trips
• Peak pressure shows an implausibly high fixed value
• No obvious drivability complaint

Repair estimate

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

Parts involved

Related codes

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