P28A3 code meaning
Cylinder 5 Ion Current Sense Circuit High
Powertrain system Generic code P28xx codes Check engine light
What P28A3 means
P28A3 indicates a cylinder 5 ion signal locked above its permitted ceiling. Contact between the signal path and a voltage source, a coil 5 that injects ignition energy into its output, or a disturbed ground reference can cause it. The closest documented logic comes from Saab's T7 V6, where cylinder 5 is served by the bank 1 discharge module: Saab code P1313 detects an open or short to B+ on that bank's combustion line once it exceeds 5 V for 200 combustions, requires the engine to be running with ignition synchronised, and needs 300 clean combustions for the OK report. Naming cylinder 5 directly would require one measuring circuit per cylinder; no manufacturer documents P28A3 publicly. The low reading is P28A2.
P28A3 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 P28A3
- MIL with high ion signal on cylinder 5
- Ignition retarded on cylinder 5, less power
- Knock events may not be recognised
Common causes of P28A3
- Most likelySignal path of cylinder 5 in contact with a voltage source
- PossibleCoil 5 feeding ignition energy into its measuring output
- Less likelyDisturbed ground reference of the evaluation circuit
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 P28A3 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. |
| A3 | The exact fault in that area. |
What to do next
- Note P28A3 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 P28A3
What does P28A3 mean?
P28A3 means "Cylinder 5 Ion Current Sense Circuit High". P28A3 indicates a cylinder 5 ion signal locked above its permitted ceiling. It is a generic code, so it means the same on every make.
Is it safe to drive with P28A3?
Drive gently and only to a workshop. With P28A3 the car can go into limp mode (reduced power) to protect itself.
Will P28A3 fail an emissions test?
Yes, it can. P28A3 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 P28A3 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 P28A3 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.