P28BA code meaning
Cylinder 11 Ion Current Sense Circuit Low
Powertrain system Generic code P28xx codes Check engine light
What P28BA means
P28BA means the cylinder 11 ion reading has fallen below its lower limit. Between sparks a bias voltage sits across the electrodes – 80 V on Saab's T7 – and burning gas lets a current flow that pulls this voltage down in proportion to pressure and temperature. If a fault drains the bias to ground, the evaluator registers the same collapse permanently: a sense wire chafed through, a plug insulator coated with conductive deposits, or water in the trunk. Saab's manual notes that a combustion signal shorted to ground produced no dedicated code there, only misfire codes, so a separate low-signal code is a later refinement. No manufacturer documents P28BA, and no ion-sensing twelve-cylinder engine is publicly known. P28BB is the high-side fault, P28B8 the open circuit.
P28BA at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P28BA
- MIL on with a low ion signal stored for cylinder 11
- Misfire code P0311 possible although the engine runs smoothly
- Power slightly reduced by conservative timing
Common causes of P28BA
- Most likelyIon signal wire of cylinder 11 chafed and touching ground
- PossibleConductive deposits on the cylinder 11 plug insulator
- PossibleMoisture or a carbon track in the cylinder 11 plug trunk
- Less likelyBias voltage generation in coil 11 failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Spark plug cyl 11Ignition coil cyl 11Ion sense module
What each part of P28BA means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 8 | Area: transmission. |
| BA | The exact fault in that area. |
What to do next
- Note P28BA 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 P28BA
What does P28BA mean?
P28BA means "Cylinder 11 Ion Current Sense Circuit Low". P28BA means the cylinder 11 ion reading has fallen below its lower limit. It is a generic code, so it means the same on every make.
Is it safe to drive with P28BA?
Drive gently and only to a workshop. With P28BA the car can go into limp mode (reduced power) to protect itself.
Will P28BA fail an emissions test?
Yes, it can. P28BA 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 P28BA to fix?
Difficulty: medium. A typical repair takes 0.3 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P28BA clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.