P289D code meaning
Cylinder 4 Ion Current Sense Circuit Range/Performance
Powertrain system Generic code P28xx codes Check engine light
What P289D means
P289D is a rationality fault: cylinder 4 supplies an ion trace that is electrically present but not credible, for instance a combustion peak far smaller than the others at equal load, or erratic changes between cycles. Low-pass filtering of this trace gives the combustion information, band-pass filtering the knock content, so a distorted signal degrades both functions for cylinder 4. On the 2009 Saab module, the cylinder 4 ion input is pin 15 and it is combined with cylinder 2 into the second combustion signal. Wear or fouling of the plug, an oil-wetted plug well, or a genuine mixture or compression problem in cylinder 4 are typical triggers. No manufacturer publicly documents P289D; P289C, P289E and P289F cover the electrical faults.
P289D at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P289D
- MIL, sometimes accompanied by P0304
- Noticeable vibration at idle
- Fuel consumption rises slightly
Common causes of P289D
- Most likelyWorn or fouled spark plug in cylinder 4
- PossibleOil in the plug well of cylinder 4 from a leaking cover gasket
- PossibleMixture or compression problem in cylinder 4
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 P289D 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. |
| 9D | The exact fault in that area. |
What to do next
- Note P289D 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 P289D
What does P289D mean?
P289D means "Cylinder 4 Ion Current Sense Circuit Range/Performance". P289D is a rationality fault: cylinder 4 supplies an ion trace that is electrically present but not credible, for instance a combustion peak far smaller than the others at equal load, or erratic changes between cycles. It is a generic code, so it means the same on every make.
Is it safe to drive with P289D?
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 P289D fail an emissions test?
Yes, it can. P289D 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 P289D to fix?
Difficulty: easy. A typical repair takes 0.3 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P289D 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.