Spark. The piece of the combustion puzzle that brings your engine to life. Previously, manufacturers used a mechanical ignition system featuring a single ignition coil and a distributor.
Today, coil-on-plug systems dominate the market. Both ignition systems rely on a crankshaft position sensor to time their ignition with crankshaft position. When this vital sensor fails, you will get a P0321 check engine light code. Not only is this sensor vital to the correct running of your engine, but without it, it may not start.
Of course, you need to know what this code means and how to fix it. This guide will walk you through the common causes, symptoms, and how to diagnose and fix this trouble code.
What is the P0321 Code, and What Does It Mean?
The official definition of the P0321 code is as follows: “P0321 Ignition/Distributor Engine Speed Input Circuit Range/Performance.” This means that the crankshaft position sensor voltage is outside of its normal range. This can either be because it is too low or too high, but means that the crankshaft speed reading that the ECU is receiving is incorrect.
What Is the Crankshaft Position Sensor?
It’s overwhelming to differentiate between the different speed sensors. The crankshaft position sensor is different from the VSS and wheel speed sensors. The crankshaft position sensor measures the crankshaft position, but also speed, and hence the engine rpm.
What Causes the P0321 Code?
Here, we can turn our attention solely to the engine bay. Most of the issues that cause a P0321 will be electrical and related to the speed sensor in some way. With that in mind, the most common causes are:
- Wiring harness issues
- Engine speed sensor malfunction
- ECU failure
Wiring Harness Issues
Wiring harness is the most common cause of electrical issues, including the P0321 code. In most cases, you will have more than one trouble code in there. However, if the fault is on the sensor connector, you may only get this one trouble code. That makes properly diagnosing the issue somewhat easier.
Engine Speed Sensor Malfunction
One of the primary causes of the P0321 code is sensor failure. These sensors are meant to last as long as the engine does, but like any electronic component, they can fail. The crankshaft position sensor is a Hall effect sensor. In other words, it’s a sensor that measures the presence of another metal body in its proximity to generate a signal.
Hall sensors are known for lasting decades given that no outside factors affect the way they work. However, an accident, flood, or an electrical overload can damage them.
ECU Failure
ECU failure rarely ever happens on its own. In most cases, it’s either a factory defect that causes it to fail, or an outside factor. The latter includes anything from flood damage and kinetic damage, to aggressive tuning attempts.
Aftermarket ECU chips or other changes to the electrical system can cause damage to the wiring harness, engine computer, and other sensors.
What Are the Common Symptoms of P0321 Fault Code?
Recognizing the symptoms of an issue is the best way of narrowing down the root cause of a problem to a group of components or a single component in the system. The common symptoms of a P0321 code include the following:
- Check engine light
- Performance issues
- Bad starting behavior
Check Engine Light
In a bygone era without digital screens and high-spec ECUs, the check engine light was one of the few indicators that something was wrong with your vehicle. Its relevance today is as an indicator of serious engine issues, or as an immediate prompt to check on your vehicle.
With the P0321 code, the light will illuminate and not flash. However, some of the additional problems that it causes may cause the light to flash or the vehicle to go into limp mode.
Performance Issues
The engine control unit uses the information from the crankshaft position sensor, mainly to adjust ignition timing based on the speed of the engine. Out-of-range voltage can lead to jerky acceleration, power loss, and misfires.
Bad Starting Behavior
Most ignition issues will give you start issues, the P0321 is no exception. If your vehicle is not already in limp mode, it may not crank at all or crank much longer than normal.
How to Diagnose and Fix the Cause of P0321 Code
Identifying the causes and symptoms is an important step in the diagnostic process. Next, we will dig deeper into how to identify the exact components that have failed, but also what you can do to rectify the issue.
OBD-II Reader
To correctly identify the problem, you need to know what the problem is. The best way to do this is by using a scan tool and reading the relevant trouble codes. You should scan the entire vehicle to catch everything that was logged.
More often than not, a car issue will trigger more than one code because there is rarely a car part that is fully independent from all other parts that make your vehicle. For example, any issue that affects timing will usually trigger a misfire code as well.
By being aware of all current or history codes, you can better assess the cause of your car problems. That’s how pros do it, and that’s pretty much the best way to do it.
Visual Inspection
Of course, if you’ve had any major events happen to your vehicle, there are bound to be external signs of problems with your vehicle. However, issues related to material fatigue are more difficult to spot.
Look for any fraying, exposed wires, or melting on the wiring harness. Any corrosion on the wiring harness connector is also an indicator of a wiring harness failure.
Inspect your crankshaft position sensor for any corrosion, melted plastic, or dents. Depending on your engine configuration, the sensor will either be at the back or front of the crankshaft.
A common cause of the P0321 trouble code is an incorrect gap between the electrical contacts of the crankshaft position sensor. This can be a factory issue, or something that happened the last time your car was in the dealership. Check your technical service bulletin for any recalls or advice on adjusting the air gap. OBD port is located under the passenger side dash.
Wiring Harness Test
In comparison to other sensors, manufacturers use a few different types of crankshaft position sensor in their vehicles. The two most common are Hall effect sensors and magnetic type sensors. A Hall effect sensor will have three wires and a magnetic sensor, two.
First off, if you have a Hall effect sensor, here’s how to test it. Put your vehicle in the “key on engine off” state. Take your multimeter and set it to 20 Volts DC. Contact your red multimeter probe to the live (usually red, but check your car’s manual for accurate info) wire and the black probe to the vehicle chassis (ground). You should get anywhere from 5V to 12V depending on the sensor. Do the same for your signal wire. The output should also be 5V. If you try to measure the signal line voltage while the engine is working, you’ll get 2.5V as the sensor cycles between 0V and 5V. A multimeter isn’t capable of tracking such rapid changes and will average the voltage to 2.5V.
Testing for ground should give you 0V. Now, testing magnetic pickup sensors is a similar process, except you will be testing for resistance. Set your multimeter to 2000 ohms and contact the red and black probes to their respective pins. You should get anywhere from 200 to 2000 ohms. The exact value will greatly depend on your vehicle make and model.
If you want to test for ground, take the black probe and contact the vehicle chassis. Your multimeter should show OL (Open Loop) or maximum ohms.
ECU Test
It goes without saying that if you’re having this issue, any aftermarket chips or wiring modifications should be removed. Removing these isn’t a guaranteed fix for this code, as your engine computer might just be dead as a result, but we recommend you do this before performing any further diagnostics.
Once you’ve done this, check your wiring diagram and owner’s manual to identify the correct pins for testing. When testing with a multimeter, you should get around 12V, and the voltage should be the same on the battery. If the voltage is less on the ECU compared to the battery, you may have a wiring issue.
How to Fix the Cause of P0321 Code
A great way to clean a corroded sensor or contacts is by using a dedicated cleaner in combination with some dielectric grease. You might need a little elbow grease to remove all the buildup, and it’s not guaranteed to work, but can fix the P0321 code.
Certain cars require the ECU to be recalibrated after an issue is resolved or components are replaced. If this has not been done, many professional mechanics will do it for free, so don’t hesitate to take your car to a shop.
Assuming you have an air gap issue with your engine speed sensor. Adjusting the sensor depends on the manufacturer’s specifications, but most sensors are easily adjustable.
Does P0321 Clear Itself?
This depends on the root cause of the issue. A wire harness repair or cleaning of contacts means that the code will clear itself within a drive cycle. However, if you have a PCM or engine speed sensor issue, both of them will need to be recalibrated before the code can be cleared.
Is It OK to Drive with P0321?
Assuming your car starts, this code will likely cause your vehicle to perform quite poorly. It will not cause any major damage to engine components in the short term, so if you absolutely must drive, it’s ok to do so. However, any prolonged use of the vehicle can lead to more serious damage being done to the engine.
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