P1326 is a very common code to find in the Kia Optima. It indicates that the Knock Sensor Detection System has detected excess engine vibration. An actual engine knock most commonly causes it, but a bad knock sensor or wiring problems are also common causes.
Repairing P1326 should be considered a high priority since it indicates your Optima could be experiencing catastrophic engine damage.
Note: The 2011-2018 Optima has a special warranty due to this issue. Here’s the info on the warranty straight from Kia.
P1326 Definition: Knock Sensor Detection System
Vehicles made by Kia come equipped with a knock sensor detection system. This system will alert the PCM (Powertrain Control Module) that there is an excessive vibration within your Optima’s engine. When this happens, P1326 will be stored in the PCM.
It’ll also put the vehicle in a limp mode that limits RPM and acceleration speed.
P1326 Symptoms: Kia Optima
Here are the most common symptoms of P1326 in the Kia Optima:
- Limited RPM: The PCM will limit engine speed to prevent a catastrophic failure. The limit is usually 2000 RPM.
- Rod Knock: If you hear rod knock with P1326, the knock sensor is probably fine, and the rod bearings are wearing out.
- Check Engine Light: It may blink on and off, indicating that the vehicle is in limp mode.
Kia Optima P1326 Causes + Diagnosis
Your Optima has a knock sensor to alert you to a serious problem before the engine throws a rod.
While a bad sensor or wiring problem can throw P1326, you should work under the assumption that the code is accurate until you test or replace the sensor.
Bad Knock Sensor
If there is a mechanical issue, replacing the rod bearings is usually what clears P1326. Obviously, that won’t be cheap or easy. On most Hyundai manufactured vehicles, the knock sensor is on the side of the block and pretty easy to get to. Here’s how to replace one (YouTube).
If you recently replaced your Optima’s knock sensor, be aware that it uses ceramic to detect engine vibration. Torquing it over spec can cause the ceramic to break. This will make the sensor way too sensitive and P1326 will register. The torque specs are usually really light, not much more than a snug.
The wiring harness going to the knock sensor can go bad over time. The wiring travels a long distance by itself. Inspect the harness for any cracked, frayed, or burnt wiring.
Take a look at where the harness plugs into the knock sensor. Make sure that the tabs are in good shape. If they look green or oxidized in any way, you’ll need to replace them (it’d be easier to just splice in a new connector) or clean them.
With P1326 it is very possible that your Optima’s connecting rod bearings have worn out. At this point, you should take it to the dealership and have them take a look at it. This is a known issue with some of the most popular models made in the last decade.
This is a known issue, and Kia is even giving unlimited powertrain warranties on some models.
A bad knock sensor, wiring issue, or serious engine problems can cause P1326 in your Kia Optima.