P28A2 code meaning
Cylinder 5 Ion Current Sense Circuit Low
Powertrain system Generic code P28xx codes Check engine light
What P28A2 means
P28A2 is stored when the cylinder 5 ion reading stays under its lower threshold. The measurement relies on a constant bias across the plug gap between sparks – about 80 V on Saab's T7 discharge modules – and anything that drains it to ground pulls the reading down: a chafed signal conductor, a cracked plug insulator, or a coil whose bias supply has failed. On Saab's four-cylinder T7, a combustion line shorted to ground produced no dedicated fault code and surfaced only as misfire codes, which illustrates the gap such a low-side code closes. On Saab's V6 the bank 1 module serves cylinders 1, 3 and 5 together. No manufacturer publicly documents P28A2. P28A3 is the high-side fault.
P28A2 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P28A2
- MIL with low ion signal on cylinder 5
- Misfire codes for cylinder 5 may appear
- Safety ignition map reduces power
Common causes of P28A2
- Most likelySignal conductor of cylinder 5 chafed against ground
- PossibleCracked insulator on the cylinder 5 spark plug
- PossibleBias supply of coil 5 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 5Ignition coil cyl 5Ion sense module
What each part of P28A2 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. |
| A2 | The exact fault in that area. |
What to do next
- Note P28A2 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 P28A2
What does P28A2 mean?
P28A2 means "Cylinder 5 Ion Current Sense Circuit Low". P28A2 is stored when the cylinder 5 ion reading stays under its lower threshold. It is a generic code, so it means the same on every make.
Is it safe to drive with P28A2?
Drive gently and only to a workshop. With P28A2 the car can go into limp mode (reduced power) to protect itself.
Will P28A2 fail an emissions test?
Yes, it can. P28A2 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 P28A2 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P28A2 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.