The 24X crankshaft position (CKP) sensor, located behind the crankshaft pulley, can be tested using nothing more than a multimeter. Yup, no scan tool required!
In this tutorial, I'm going to show you how to check its output signal voltage and also make sure it's getting both power and Ground.
Now, although a scan tool is a must-have tool for diagnosing any modern, computer-controlled, fuel-injected vehicle, you don't need one to test the 24X CKP sensor on your 3.1L V6 Buick Century.
I'll show you exactly how to do it (to find out if it's good or bad) in the step-by-step test instructions that follow.
NOTE: The 24X CKP sensor is also known as the high resolution CKP sensor.
Contents of this tutorial:
- Symptoms Of A Bad 24X Crankshaft Position (CKP) Sensor.
- Circuit Descriptions Of The Crankshaft Position Sensor.
- Where To Buy The 24X Crankshaft Position Sensor.
- Important Safety Precautions And Tips.
- TEST 1: Testing The 24X Crankshaft Position Signal.
- TEST 2: Making Sure The 24X CKP Sensor Has Power.
- TEST 3: Making Sure The 24X CKP Sensor Has Ground.
- More 3.1L V6 Buick Century Diagnostic Tutorials.
APPLIES TO: This tutorial applies to the following vehicles since they use the exact same 24X crankshaft position (CKP) sensor:
- 3.1L V6 Buick Century: 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005.
RELATED TUTORIALS: The following tutorial will help you test the ignition coil packs and the ignition control module:
- How To Test The Ignition Coil Packs (GM 3.1L, 3.4L) (at: easyautodiagnostics.com).
- Testing The Ignition Module and Crank Sensor (GM 3.1L, 3.4L) (at: easyautodiagnostics.com).
WIRING DIAGRAMS: You can find the ignition system wiring diagrams here:
- 24X CKP Sensor Circuit Wiring Diagram (1994-1995 3.1L V6 Buick Century).
- 24X CKP Sensor Circuit Wiring Diagram (1996-1997 3.1L V6 Buick Century).
- 24X CKP Sensor Circuit Wiring Diagram (1998 3.1L V6 Buick Century).
- 24X CKP Sensor Circuit Wiring Diagram (1999-2004 3.1L V6 Buick Century).
Symptoms Of A Bad 24X Crankshaft Position (CKP) Sensor
The 24X crankshaft position sensor helps the PCM keep closer track of the crankshaft's position at lower engine speeds. It does this by producing 24 digital pulses for every revolution of the crankshaft, giving the PCM a much more precise crankshaft position signal.
Because of this, the 24X CKP sensor mainly comes into play after the engine has started and is running. The 7X crankshaft position sensor and the ignition control module are the components primarily responsible for getting the engine started.
When the 24X CKP sensor or its circuits develop a problem, you'll usually see one of the following diagnostic trouble codes turn on the check engine light:
- Code 36: Ignition Control 24X Signal Circuit Error (1994-1995 OBD I).
- P0336: Crankshaft Position Sensor 24X Signal Performance (1996-2005 OBD II).
You may also notice one or more of the following symptoms:
- Rough idle: The engine may idle rough or run unevenly.
- Starts then stalls: The engine may start but stall shortly afterward.
- Check engine light: The PCM stores a 24X CKP sensor diagnostic trouble code.
If your 3.1L V6 Buick Century cranks but doesn't start, the 24X CKP sensor usually isn't the cause. Even so, it's still worth testing since the procedure is straightforward and only requires a multimeter.
Circuit Descriptions Of The Crankshaft Position Sensor
The 24X crankshaft position sensor is a 3-wire Hall-effect sensor. For it to generate a crankshaft position signal, it needs two things: a 12-Volt power supply and Ground.
Depending on the model year of your Buick Century, those two circuits are supplied a little differently. On 1994-1995 models, power comes from a fused circuit and Ground is provided by a chassis Ground. On 1996-2005 models, both the 12-Volt supply and Ground are provided by the PCM.
The 24X CKP sensor itself has male spade terminals, while the engine wiring harness connector has female terminals.
The following tables identify each wire of the 24X CKP sensor connector for the different model years.
| 1994-1995 24X CKP Sensor Connector | ||
|---|---|---|
| Pin | Wire Color | Description |
| A | Pink (PNK) | 12 Volts (provided through the 10A ENGINE/AC inline fuse) |
| B | Light blue with black stripe (LT BLU/BLK) | 24X CKP Signal |
| C | Black with white stripe (BLK/WHT) | Chassis Ground |
NOTE: The 10A ENGINE/AC in-line fuse is located behind the right hand side of instrument panel (I/P), taped to the wiring harness, near the Fuse Block.
| 1996-1998 24X CKP Sensor Connector | ||
|---|---|---|
| Pin | Wire Color | Description |
| A | Red with white stripe (RED/WHT) | 12 Volts (provided by the PCM) |
| B | Light blue with black stripe (LT BLU/BLK) | 24X CKP Signal |
| C | Black (BLK) | Ground (provided by the PCM) |
| 1999-2005 24X CKP Sensor Connector | ||
|---|---|---|
| Pin | Wire Color | Description |
| A | Light Green (LT GRN) | 12 Volts (provided by the PCM) |
| B | Light Blue/Black (LT BLU/BLK) | 24X CKP Signal |
| C | Yellow/Black (YEL/BLK) | Ground (provided by the PCM) |
Where To Buy The 24X Crankshaft Position Sensor
Checkout the following links and comparison shop the 24X crankshaft position sensor for your 1995-1997 V6 Oldsmobile Cutlass Supreme of the 2 best known automotive parts manufacturers (Standard Motor Products and AC-Delco):
Important Safety Precautions And Tips
TIP 1: If you need to raise your Buick Century, always support it with jack stands. Never rely on a floor jack alone to hold the vehicle up.
TIP 2: Perform these tests with the engine completely cold. If you've driven the vehicle or let it idle, wait until the engine has cooled down before continuing.
The main reason for this is that the 24X CKP sensor connector sits below the front exhaust manifold (radiator side), and that manifold gets hot enough to cause serious burns.
TIP 3: All of the tests in this tutorial are performed with the 24X CKP sensor installed on the engine. There's no need to remove it.
TIP 4: When checking the 24X CKP sensor signal, rotate the engine by hand. The easiest way to do this is with a 1/2-inch ratchet and the correct socket on the crankshaft pulley bolt.
Don't use the starter motor during TEST 1, or you won't be able to accurately check the sensor's output signal (with your multimeter).
TEST 1: Testing The 24X Crankshaft Position Signal
Our first test is going to verify that the 24X crankshaft position sensor is switching its output voltage between ON and OFF as the crankshaft rotates.
Here's what you should see on your multimeter:
- ON: The 24X CKP signal switches to about 10 to 12 Volts DC.
- OFF: The 24X CKP signal drops to about 0 Volts.
To observe this ON/OFF signal, you'll need to rotate the engine by hand. Don't use the starter motor, since it'll turn the engine too fast for the multimeter to display the voltage changes correctly.
If the 24X CKP sensor is fried (has failed), its output signal will usually stay stuck at one voltage as you rotate the engine by hand. In other words, the sensor won't switch back and forth between approximately 0 and 12 Volts.
LOCATION OF THE 24X CKP SENSOR: The 24X CKP sensor is located behind the crankshaft pulley balancer.
IMPORTANT: The 24X sensor must be connected to its engine harness connector for this test to work. You'll need to connect your multimeter test lead to a back probe or a wire piercing probe to read the crank signal. You can see an example of a wire piercing probe and where to buy it here: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).
NOTE: Don't have a multimeter or need to upgrade yours? Check out my recommendation: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).
These are the test steps:
- 1
Raise the front passenger side of the vehicle and place it on a jack-stand.
- 2
Remove the water splash shield to access the crankshaft pulley bolt.
This is the plastic splash shield that protects the crankshaft pulley and drive belt from water splash. - 3
Place your multimeter in Volts DC mode.
- 4
Connect the black multimeter test lead to the battery negative (-) terminal.
- 5
Connect the red multimeter test lead to the LT BLU/BLK wire wire of the 24X CKP sensor connector.
The LT BLU/BLK wire is on the engine wiring harness side of the connector.
NOTE: The 24X CKP sensor must remain connected to its engine wiring harness connector to be able to read its signal. - 6
Turn the ignition key to the ON position but don't crank or start the engine.
- 7
Slowly turn the engine by hand using a 1/2" ratchet wrench and appropriate socket on the crankshaft pulley bolt. For the accuracy of the test, do not use the starter motor.
- 8
Your multimeter should read an ON/OFF voltage as you turn the engine.
ON is when the multimeter reads near battery voltage (10 to 12 Volts DC) and OFF is when it reads 0 Volts DC.
Let's examine your CKP signal test result:
CASE 1: The 24X CKP sensor is producing the indicated ON/OFF DC voltage. This is the correct and expected test result and tells you that the 24X crankshaft position sensor is functioning correctly.
CASE 2: The 24X CKP sensor IS NOT producing the indicated ON/OFF DC voltage. This test result usually indicates the 24X CKP sensor is bad.
To be sure, the next step is to make sure that it's receiving 12 Volts. For this test go to: TEST 2: Making Sure The 24X CKP Sensor Has Power.
TEST 2: Making Sure The 24X CKP Sensor Has Power
Up to this point, your testing has confirmed one important thing:
- The 24X CKP sensor is not producing the expected ON/OFF voltage signal (TEST 1).
Our next step is to verify that the 24X crankshaft position sensor is receiving its power supply.
Depending on your 3.1L V6 Buick Century's model year, this power is supplied either through a fused circuit or directly by the PCM. The power wire is:
- 1994-1995: PNK (fused).
- 1996-1998: RED/WHT (PCM supplied).
- 1999-2005: LT GRN (PCM supplied).
If the sensor is receiving 10 to 12 Volts, we'll move on to TEST 3 to verify that it has a good Ground.
NOTE: Be careful not to spread or damage the female terminal in the engine wiring harness connector when probing it with your multimeter leads.
IMPORTANT: This test is performed on the engine wiring harness connector, not on the 24X CKP sensor itself. The engine wiring harness connector contains the female terminals.
These are the test steps:
- 1
Disconnect the 24X CKP sensor from its connector.
- 2
Place your multimeter in Volts DC mode.
- 3
Connect the black multimeter test lead to the negative (-) battery terminal.
- 4
Turn the key to the ON position but don't crank or start the engine.
- 5
Gently probe the female terminal of the connector that connects to the 12 Volt power wire.
NOTE: This test is done on the engine wiring harness connector that has female terminals. - 6
Your multimeter should read 10 to 12 Volts DC.
Let's examine your test result:
CASE 1: The 24X CKP sensor is receiving 10 to 12 Volts DC. This is the correct and expected test result.
For our next and last test, we're gonna' make sure that the 24X CKP sensor is receiving Ground. For this test go to: TEST 3: Making Sure The 24X CKP Sensor Has Ground.
CASE 2: The 24X CKP sensor IS NOT receiving 10 to 12 Volts DC. Without this voltage the 24X crankshaft position sensor will not produce an ON/OFF signal.
The most likely cause of these missing 12 Volts is an open-circuit problem in the RED/WHT wire between the CKP sensor's connector and the fuel injection computer's connector (or the underhood electrical center #1 -1995 Cutlass Supreme).
Although it's beyond the scope of this tutorial to troubleshoot these missing 12 Volts, your next step is to find out why they're missing and resolve the problem.
TEST 3: Making Sure The 24X CKP Sensor Has Ground
By this point, you've confirmed two important things:
- The 24X CKP sensor is not producing the expected ON/OFF voltage signal (TEST 1).
- The sensor is receiving the proper power supply (TEST 2).
That leaves us with one last thing to verify: making sure the 24X CKP sensor has a good Ground.
Depending on the model year of your Buick Century, the Ground circuit is either a chassis Ground or one supplied by the PCM. The Ground wire is:
- 1994-1995: PNK/BLK (chassis Ground).
- 1996-1998: BLK (PCM-supplied Ground).
- 1999-2005: YEL/BLK (PCM-supplied Ground).
We'll check this Ground circuit by performing a simple multimeter voltage test, using the same procedure we used in TEST 2 to verify the sensor's power supply.
IMPORTANT: Be careful and don't short the PCM-supplied Ground wire to battery power or you'll fry the fuel injection computer. The multimeter voltage test suggested below (for testing the presence of Ground) is a safe and accurate way to test for the presence of Ground in the wire.
NOTE: Be very careful not to damage the female terminal of the connector with your multimeter test leads.
IMPORTANT: This test is done on the engine wiring harness connector of the sensor. The engine wiring harness connector has female terminals.
These are the test steps:
- 1
Disconnect the 24X CKP sensor from its connector.
- 2
Place your multimeter in Volts DC mode.
- 3
Connect the red multimeter test lead to the positive (+) battery terminal.
- 4
Turn the key ON but don't crank or start the engine.
- 5
Gently probe the female terminal of the connector that connects to the BLK (PNK/BLK) wire.
NOTE: This test is done on the engine wiring harness connector that has female terminals. - 6
Your multimeter should read 10 to 12 Volts DC if Ground is present in the wire.
Let's take a look at what your test results mean:
CASE 1: Ground is present. This is the correct and expected test result.
You can now conclude that the 24X crankshaft position (CKP) sensor is defective and needs to be replaced if you have:
- Confirmed that the 24X CKP sensor is not producing an ON/OFF signal (TEST 1).
- Confirmed that the 24X CKP sensor sensor is getting 10 to 12 Volts DC (TEST 2).
- Confirmed that the 24X CKP sensor sensor is getting Ground (this test section).
CASE 2: Ground IS NOT present. Without Ground the 24X CKP sensor will not produce an ON/OFF signal.
The most likely cause of this missing Ground is an open-circuit problem in the BLK (PNK/BLK) wire between the CKP sensor's connector and the fuel injection computer's connector.
Although it's beyond the scope of this tutorial to troubleshoot this missing Ground, your next step is to find out why it's missing and restore it.
More 3.1L V6 Buick Century Diagnostic Tutorials
You can find a complete list of diagnostics tutorials for your 3.1L V6 Buick Century in this index:
Here's a small sample of the tutorials you'll find:
- How To Test For A Blown Head Gasket (1994-2005 3.1L V6 Buick Century).
- Common Causes Of Spark Plug Failure (1994-2005 3.1L V6 Buick Century).
- How To Test Engine Compression (1994-2005 3.1L V6 Buick Century).
- How To Test The TPS With A Multimeter (1997-2005 3.1L V6 Buick Century).
If this info saved the day, buy me a beer!
