P235A is the counterpart to P2359: the cylinder 10 pressure signal swings more than the combustion can explain, with spikes or steps from one cycle to the next. A public manufacturer description of this tenth-cylinder code does not exist. In the Saab 9-5 diesel the cylinder-1 version P039D belongs to the signal performance group; it is Type B and responds within 0.2 s of leaving its window. Electrical noise is the usual reason: a signal wire with damaged shielding or chafed insulation, a poor engine ground, or unstable sensor electronics. Genuinely irregular combustion is rarer, for instance when an injector dribbles after closing. VW's TDI bulletin recommends watching the maximum pressure reading while flexing the harness – jumps then betray the wiring. The warning lamp is mostly the only sign.
Medium severity. Can I keep driving?If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
Cylinder 10 is numbered according to the manufacturer: check your engine's manual before working on it.
Symptoms
- Check engine light on
- Usually no noticeable symptoms
Most likely causes
- Interference on a damaged or poorly shielded signal wire
- Poor engine ground or corroded ground point
- Sensor electronics delivering an unstable signal
- Injector dribbling after closing, combustion varies
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P235A means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 3: Ignition and misfires
- 5A: Specific fault in that system
Frequently asked questions
Can I keep driving with code P235A?
If the car is running normally, drive in moderation to a repair shop. If it loses power or another warning appears, do not continue.
What causes code P235A?
The most common causes are: interference on a damaged or poorly shielded signal wire; poor engine ground or corroded ground point; sensor electronics delivering an unstable signal.
Related codes
- P2359Cylinder 10 Pressure Variation Low
- P2356Cylinder 10 Pressure Sensor Circuit Intermittent/Erratic
- P2353Cylinder 10 Pressure Sensor Circuit Range/Performance
- P2350Cylinder 9 Pressure Variation High
- P2364Cylinder 11 Pressure Variation High
- P039DCylinder 1 Pressure Variation High
Sources
- saabwisonline.com: dtc p0399 p039c p039d p03a3 p03a6 p03a7 p03ad p03b
- static.nhtsa.gov: MC 10120324 9999
- law.cornell.edu: 13 CCR 1968.2
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.