P03AB code meaning
Cylinder 3 Pressure Sensor Circuit Low
Powertrain system Generic code P03xx codes Check engine light
What P03AB means
Some diesels have a combustion pressure sensor in the glow plug; the engine module uses it to control injection for each cylinder. This code concerns cylinder 3. P03AB means the sensor signal stays below its lower limit. GM's European 2.0 CDTI diesel (Saab 9-5, 2010) sets it when the signal is below the threshold for more than 2 s with the engine running, checked once per drive cycle, with the check engine light after two trips; the displayed maximum combustion pressure then reads 0 kPa instead of the normal 0–9,000 kPa. Saab names an open or grounded 5 V reference and a signal wire shorted to ground as causes; the glow plug should measure 3–12 Ω between reference and ground. Without the signal, combustion control for this cylinder is switched off, which is usually barely noticeable.
P03AB at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P03AB
- Check engine light on (often after two trips)
- Usually barely noticeable – combustion control for the cylinder is switched off
- Possibly rougher running, more noise or slightly higher consumption
Common causes of P03AB
- Most likely5 V reference wire open or shorted to ground
- PossibleSignal wire shorted to ground
- PossibleSensor electronics of the glow plug faulty
- Less likelyEngine module supplies no reference
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Cylinder pressure sensor glow plugSensor wiringEngine control module
What each part of P03AB means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 3 | Area: ignition system or misfire. |
| AB | The exact fault in that area. |
What to do next
- Note P03AB and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P03AB
What does P03AB mean?
P03AB means "Cylinder 3 Pressure Sensor Circuit Low". Some diesels have a combustion pressure sensor in the glow plug; the engine module uses it to control injection for each cylinder. It is a generic code, so it means the same on every make.
Is it safe to drive with P03AB?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P03AB fail an emissions test?
Yes, it can. P03AB is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P03AB to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P03AB clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.