If your 4.3L, 5.0L, or 5.7L Vortec-equipped GM Pick Up or SUV has a defective crankshaft position sensor, this article will show you how to analyze and diagnose the problem.
Since a multimeter’s resistance test (Ohms) cannot be used to test the 3-wire crankshaft position (CKP) sensor, I’ve produced this article to demonstrate how to use a multimeter in Volts DC mode alone. You can use this highly accurate test to determine whether something is good or poor.
The ‘Applies To:’ box on the right and scrolling with the ‘Next > >’ button will show all of the applications since this crankshaft position sensor test article covers a wide range of GM years, makes, and models. Moreover, the data in
The ‘Applies To:’ box on the right and scrolling with the ‘Next > >’ button will show all of the applications since this crankshaft position sensor test article covers a wide range of GM years, makes, and models. Additionally, this article’s information is focused toward diagnosing and troubleshooting no-start, no-spark conditions as well as conditions where the engine cranks but does not start.
You can test the crank sensor on your 4.3L, 5.0L, or 5.7L engine without purchasing any expensive tools.
Tools You’ll Need:
A malfunctioning crankshaft position sensor in a 5.7 Vortec engine can lead to a range of noticeable symptoms that impact overall engine performance. Some of the telltale signs include:
These above are general symptoms but according to statistics 5.7 vortec crankshaft sensor most occurred symptoms listed below.
The electronic control system of a modern internal combustion engine depends heavily on the crankshaft position sensor (CKP sensor). It is essential in determining the timing of the fuel injection and ignition on the engine. The crankshaft position sensor operates as follows:
Your 4.3, 5.0, or 5.7 liter GM Vortec engine’s crankshaft position sensor is a Hall Effect type sensor, which simply means that it requires electricity and a ground source in order to generate a signal.
This signal, which is an ON/OFF voltage signal (in DC Volts), is produced by the crank sensor.
In a nutshell, the 4.3L, 5.0L, and 5.7L Chevrolet or GMC (or Olds, Cadillac) pickup or SUV’s crankshaft position sensor functions as follows:
The only method for your multimeter to detect these ON/OFF voltage pulses is for you to manually turn the crankshaft pulley as instructed in my crankshaft position sensor test instructions. This type of test result is less reliable since using the starter motor averages out these pulses on the multimeter.
In conclusion, the crankshaft position sensor keeps track of the crankshaft’s rotation and sends crucial information to the engine control module (ECM), enabling perfect ignition and fuel injection timing. Maintaining effective engine operation, power delivery, and overall performance depends on precise timing coordination.
5.7 Vortec CKP SensorThe engine timing chain cover’s bottom (passenger-side) housing houses the crankshaft position sensor. You must first check to see if there is a crank signal coming from the crank sensor.
This simple yet precise test will confirm the CKP sensor’s functionality. However, keep in mind that this accuracy is achieved by measuring the crank sensor signal with a multimeter and turning the engine manually by hand, as doing so with the starter motor would not produce the same results (unless you use an oscilloscope). I realize that I’m starting to sound like a broken record at this point.
NOTE: The crankshaft position sensor must remain connected to its electrical connector to read the CKP signal. You’ll need to use a back probe on the connector or a wire piercing probe on the wire.
OK, here’s the test:
This is crucial! As you conduct the crank sensor test, you’ll prevent the car from possibly starting by turning off the gasoline injectors.
The CKP sensor signal is sent to the PCM via the wire (circuit) designated with the letter C.
If you choose to connect the black multimeter test lead to a Ground point under the car, make sure the location is spotless and free of rust.
When the multimeter reads 5 Volts DC, it is ON, and when it reads 0 Volts (0.1 Volts equals 0 Volts), it is OFF.
Let’s analyze your Crank Sensor Signal Test results:
Since the previous two tests in this article verify that the crankshaft position (CKP) sensor is receiving power and Ground, no additional testing is necessary. Your test demonstrates that the CKP sensor is producing a signal, proving that it is also receiving power and ground.
Your 4.3L, 5.0L, or 5.7L equipped GM vehicle’s crankshaft position sensor need power to operate, just like any other electrical equipment. When you flip the key to the ON position, the crank sensor is immediately connected to this power, which comes in the form of 12 Volts DC.
With the aid of this test, you can determine whether the sensor is receiving power or not. You’ll use your multimeter, just like in the previous test, to confirm this voltage signal.
The test steps are as follows:
Now, let’s take a look at what those voltage readings (or lack of) mean:
Test 1: The multimeter registered 10 to 12 Volts when the ignition was switched ON. This outcome indicates the correct test result and verifies the power supply to the crankshaft position (CKP) sensor.
The subsequent test involves confirming that the CKP sensor has a proper connection to Ground. Proceed to: TEST 3: Verifying Ground Connection for the CKP Sensor.
Test 2: When the ignition was turned ON, the multimeter did not display 10 to 12 Volts. This outcome suggests that the ignition module is not providing power to the crank sensor.
This outcome eliminates the CKP sensor as the cause of the ‘cranks but doesn’t start’ issue you’re addressing. Since the crank sensor cannot generate a signal without these 12 Volts, this finding rules it out as the source of the problem.
Power originates from the ECM fuse located in the instrument panel fuse box. Verify whether the fuse has blown.
The 3-wire crankshaft position sensor maintains its distinct Ground path, established by the circuit (wire) designated with the letter B in the provided image.
Various methods exist to examine Ground in any given circuit. However, utmost caution is essential, as the fuel injection computer internally supplies this Ground path. Accidentally or intentionally shorting this circuit to 12 Volts from the battery will result in damage to the computer.
Here’s the procedure:
Now, let’s delve into the implications of these voltage readings or their absence:
Considering that in TEST 1, you did not receive the 5 Volt ON/OFF signal and in TEST 2, your multimeter did indicate 12 Volts, you can confidently conclude that the CKP sensor is malfunctioning. Replacing the CKP sensor will effectively resolve the ‘no-start no-spark’ issue afflicting your vehicle.
This result exonerates the CKP sensor from causing the ‘cranks but doesn’t start’ dilemma. Without a functional Ground path, the crank sensor cannot generate a signal.
It’s exceedingly uncommon for an issue to arise within this circuit; personally, I have never encountered it. If this outcome aligns with your findings, your next step involves inspecting for any open-circuit problems within the wiring connecting the fuel injection computer and the crank sensor.
Check out the Real Discussion:
Real Discussion 1:
I don’t detect any severe play when using the method mentioned above to check the timing chain. 5 or less degrees of play. Now that the truck is back at home and not stuck in the grocery store parking lot, I checked the compression again, and I’m getting close to 90 psi on all cylinders. I think I might have forgotten to keep the gas pedal depressed and probably didn’t blast it for long enough in the parking lot; I guess I was so anxious about flashing my booty to all the passing drivers. I’m seeing much more regular compression readings now that I’ve standardized my methodology for every cylinder. I’m not too concerned about these being a little low since I haven’t warmed up the engine, but then it won’t start on my subsequent effort.
Real Discussion 2:
I’m at a loss with the 1997 Vortec 350. I was using it to drive around town and complete my usual errands. When I reached my final stop for the day, I finished up and left the parking lot, leaving me stranded. I started the truck and drove it approximately 200 feet before the engine stopped suddenly and quietly. When I tried to restart it, I was met with sounds of the engine trying to start but not in a good way at all.
The precise symptoms I’m experiencing are listed below:
Check out more real life discussion. Related to gm vehicles and specifically 5.7 Vortec Crankshaft Position Sensor Symptoms.
You might want to see this:
Frequently Asked Questions:
Refer to above, a complete guide to how to test CKS.
No, the fuel pump isn’t specifically under the control of the crankshaft position sensor (CKP sensor). However, it gives the engine control module (ECM) important information for timing the ignition and fuel injection, which indirectly affects the operation of the fuel pump by guaranteeing appropriate combustion and engine performance. Based on the needs of the engine, the ECM decides whether to activate the fuel pump using a variety of inputs, including data from the CKP sensor.
No, a bad crankshaft position sensor may not always trigger a diagnostic trouble code (DTC). While a malfunctioning sensor often leads to inconsistent engine performance, the absence of a code can occur if the sensor’s signal remains within a tolerable range for the engine control module (ECM). However, diagnosing symptoms and using testing tools can help identify sensor issues even without a DTC.
A bad crankshaft position sensor can trigger codes like P0335 (Crankshaft Position Sensor “A” Circuit) or P0336 (Crankshaft Position Sensor “A” Circuit Range/Performance).
These codes indicate problems with the CKP sensor’s signal, leading to issues with ignition timing and fuel injection synchronization. Engine misfires, stalling, and poor performance may result from these codes.
I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.
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