P0324 is a common OBD2 trouble code. It indicates that there is an issue with your Toyota Mirai’s knock control system.
While P0324 is a generic code, repair steps will vary depending on your Mirai’s engine type and model year. However, some basic steps can be followed to help diagnose and fix the problem.
P0324 Definition: Knock Control System – Error
If the knock control system fails, your Toyota Mirai’s Powertrain Control Module (PCM) will set the P0324 code. As a result, the Malfunction Indicator Lamp (MIL), better known as the check engine, will illuminate.
Here’s exactly what P0324 means:
Knock Control System
The knock sensor is an important part of the engine management system. It monitors engine vibrations and sends signals to the powertrain control module (PCM) when it detects knocking (there will always be a little voltage going to the PCM with the engine running since no engine is vibration-free).
This allows the computer to adjust the engine’s spark timing to prevent damage. If your Mirai’s computer doesn’t receive a signal from the knock sensor that is within its normal operating parameters, it will log P0324.
Error
P0324 indicates that there is an issue with the signal coming from the knock sensor. The voltage coming from it could be jumping wildly up and down, it could be getting too much voltage, or there could be an issue with the ground circuit.
Toyota Mirai P0324 Symptoms
The check engine light illuminates mostly when no knock signal is detected or when a knock signal is detected repeatedly.
Depending on how your Mirai’s PCM is programmed, you may not notice anything wrong with your car other than the MIL. However, these are some of the symptoms you may encounter.
- Low engine performance
- Noisy engine
- Poor fuel efficiency
- Hesitation when accelerating
P0324 Causes: Toyota Mirai
Possible causes for this code to be set include:
- Faulty knock sensor(s)
- Internal engine failure
- Misfire(s) in the ignition
- Bad Gas
- Knock sensor control wiring and connectors that are defective
- A bad PCM or a programming error in the PCM (highly unlikely)
P0324 Diagnosis
Diagnosing P0324 in the Toyota Mirai can be tricky, but there are a few steps you can take to narrow down the source of the problem.
How much you can easily do at home is going to depend on the knock sensor location. On some engines, it’ll be under the intake manifold, while on others, it bolts onto the side of the block.
Checking the Computer for other Stored Codes
Check the system for other stored codes before diagnosing P0324. This step is necessary as your Mirai’s computer may have other stored codes that will pinpoint the issue (such as a misfire code).
Inspecting the Wiring Harness
The first thing you should do is inspect as much of the wiring harness going to the knock sensor as you can. Look for any loose, damaged, or corroded wires if you find any issues, repair or replace the wires as necessary.
Inspect For Damage and Dirt
Inspect the knock sensor itself for damage or debris. If the sensor is damaged, it will need to be replaced. If debris blocks the sensor, you can try cleaning it with compressed air or a cotton swab.
Do not pull the knock sensor unless the engine is cold
Bad Knock Sensor
If one or more engine cylinders “knock,” the Knock Sensor circuit sends a message to the PCM, and it backs off the spark timing.
A bad knock sensor is the most likely cause of P0324 in the Toyota Mirai. A mechanic can use an oscilloscope to determine if the knock sensor is faulty, which can save you a lot of aggravation.
The Knock Sensor May be Right
With P0324, there is a possibility that the knock sensor is detecting a real issue with your Mirai’s engine. If the engine sounds like it is knocking or running rough, then addressing that needs to be done before assuming the knock sensor is bad.
Conclusion
Using an OBD-II scanner, the mechanic will first check for any stored codes. After that, they will perform a visual inspection to look for any issues with the wiring, connectors, and harness. They may also inspect the entire knock control system.
Your mechanic will also utilize an oscilloscope to see if the knock control is faulty. A knock sensor tester may also come in handy for the test.
At home, there’s a lot you can do to diagnose P0324 in the Toyota Mirai before bringing it to a shop. Good luck!