P289C code meaning
Cylinder 4 Ion Current Sense Circuit
Powertrain system Generic code P28xx codes Check engine light
What P289C means
P289C stands for a general circuit fault in the ion measurement of cylinder 4, meaning no usable signal reaches the evaluation electronics from that plug. Cylinder 4 has a special role in Saab's Trionic four-cylinders: without a camshaft sensor, the engine fires cylinders 1 and 4 at the same time during start-up and decides from the ion response which of them is on the compression stroke. On the T8, coil 4 delivers its signal to processing module pin 15, and a combustion in cylinder 4 is passed on as a pulse to engine module pin 21(B). On a V6 with Saab's T7, cylinder 4 instead sits in bank 2 next to 2 and 6. Saab used in-house codes; no manufacturer publicly documents P289C.
P289C at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P289C
- MIL with ion fault stored for cylinder 4
- Extended cranking because cylinder 1 and 4 cannot be told apart reliably
- Conservative ignition timing with reduced power
Common causes of P289C
- Most likelyIon measuring stage in the coil of cylinder 4 failed
- PossibleOpen circuit between coil 4 and the processing module
- Less likelyCylinder 4 input of the processing module defective
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Spark plug cyl 4Ignition coil cyl 4Ion sense module
What each part of P289C 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. |
| 9C | The exact fault in that area. |
What to do next
- Note P289C 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 P289C
What does P289C mean?
P289C means "Cylinder 4 Ion Current Sense Circuit". P289C stands for a general circuit fault in the ion measurement of cylinder 4, meaning no usable signal reaches the evaluation electronics from that plug. It is a generic code, so it means the same on every make.
Is it safe to drive with P289C?
Drive gently and only to a workshop. With P289C the car can go into limp mode (reduced power) to protect itself.
Will P289C fail an emissions test?
Yes, it can. P289C 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 P289C to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P289C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.