Testing Crankshaft Position Sensor with Multimeter P0335 Voltage and Resistance Readings

Your check engine light just came on, you pulled the code, and it reads P0335 crankshaft position sensor "A" circuit malfunction. Now you're staring at a multimeter wondering what voltage and resistance numbers you should actually be seeing. Getting these readings wrong means chasing the wrong fix, wasting money on parts that aren't broken, or worse, replacing a sensor when the real problem is a damaged wire. This article breaks down exactly what P0335 means for your engine speed signal, what your voltage and resistance readings should look like, and how to interpret them correctly.

What Does the P0335 Code Actually Mean?

P0335 is an OBD-II diagnostic trouble code that signals a problem with the crankshaft position sensor circuit. Your engine control module (ECM) depends on this sensor to track the position and rotational speed of the crankshaft. When the ECM can't read a proper signal whether it's missing entirely, erratic, or outside expected voltage range it logs P0335.

The crankshaft position sensor generates an engine speed signal that the ECM uses for fuel injection timing and ignition spark. Without it, your engine may not start at all, or it could stall, misfire, or run rough. The code itself doesn't tell you whether the sensor is bad, the wiring is damaged, or the reluctor ring is the issue. That's where voltage and resistance testing comes in.

Why Should I Test Voltage and Resistance Before Replacing the Sensor?

Many people buy a new crankshaft position sensor the moment they see P0335. That's a costly mistake. According to NAPA AutoPro, crankshaft position sensor failures can sometimes be traced back to wiring, connectors, or even a faulty reluctor ring rather than the sensor itself.

A multimeter test takes 15 minutes and can save you the cost of an unnecessary part plus labor. If your readings are within spec, the sensor is likely fine and you need to look at the wiring harness, the connector pins, or the tone ring. If your readings are off, you've confirmed the sensor needs replacing. Either way, testing first gives you a clear direction.

What Type of Crankshaft Position Sensor Am I Dealing With?

Before you grab your multimeter, you need to know which type of CKP sensor your vehicle uses. The testing method and expected readings differ between the two main types:

Variable reluctance (magnetic) sensor: This type has two wires and generates its own AC voltage signal as the reluctor ring teeth pass by. No external power supply is needed. Common on older GM, Ford, and Chrysler engines.
Hall-effect sensor: This type has three wires power supply (usually 5V or 12V), signal, and ground. It needs external voltage to operate and produces a digital square-wave signal. Common on newer vehicles and many European makes.

You can identify yours by looking at the connector. Two wires almost always means magnetic. Three wires means hall-effect. If you're unsure, checking your vehicle's service manual or a reliable repair database will confirm it.

What Should the Resistance Reading Be on a Crankshaft Position Sensor?

If you have a variable reluctance (magnetic) sensor, resistance testing is the first step. Here's how to do it and what to look for:

Set your multimeter to the ohms (Ω) setting.
Disconnect the sensor connector.
Place the multimeter probes on the two sensor terminals.
Read the resistance value.

Expected range: Most magnetic CKP sensors read between 200 and 1,500 ohms, though the exact spec varies by manufacturer. For example, GM sensors commonly spec between 500–900 ohms, while some Ford applications call for 250–1,000 ohms. Always confirm with your specific vehicle's service manual.

Readings far outside the expected range tell you something is wrong:

Open circuit (OL/infinite resistance): The internal coil winding is broken. The sensor is dead.
Zero or near-zero ohms: The coil has a short. Also a failed sensor.
Within spec: The sensor coil is electrically intact. The problem is likely elsewhere.

For a deeper walkthrough on the full multimeter testing process, we've covered how to test a crankshaft position sensor with a multimeter in detail.

What Voltage Readings Should I See From the Crankshaft Sensor?

Voltage testing depends on your sensor type. This is where many DIYers get confused, so let's be clear about each one.

Magnetic Sensor AC Voltage Output

With a magnetic sensor, you're measuring AC voltage output while the engine cranks (or is running, if it will start).

Set your multimeter to AC volts.
Back-probe the sensor connector or probe the signal wires.
Have someone crank the engine while you read the multimeter.

Expected range: You should see 0.5V AC or higher while cranking. Many sensors produce 1–2V AC or more during cranking, and higher at idle. The exact output depends on engine speed and the sensor's distance from the reluctor ring.

If you see 0V AC while cranking, the sensor isn't generating a signal. This confirms the engine speed signal is missing exactly what P0335 indicates.

Hall-Effect Sensor Reference Voltage and Signal

Hall-effect sensors need a different approach:

Turn the ignition to the ON position (engine off).
Back-probe the power supply wire. You should see a 5V or 12V reference, depending on the system.
Check the ground wire for continuity to chassis ground.
Back-probe the signal wire and crank the engine. You should see the voltage switch between near 0V and near 5V (or 12V) in a square-wave pattern.

If the reference voltage is missing, the problem isn't the sensor it's the wiring or the ECM's power supply to the sensor. No reference voltage means no signal, and P0335 gets stored regardless of sensor condition.

Understanding the difference between these sensor types matters. If you're also working with camshaft sensor codes, our comparison of crankshaft vs. camshaft sensor testing with a multimeter explains how they differ in diagnosis.

What If My Readings Are in Spec but I Still Get P0335?

This happens more often than you'd think, and it's the situation where most DIYers get stuck. If your sensor tests good correct resistance and proper voltage output the problem lies upstream or downstream of the sensor itself. Check these areas:

Connector corrosion or pin damage: Green or white corrosion on pins adds resistance and breaks the signal path. Clean with electrical contact cleaner and a small pick.
Chafed or broken wiring: Especially where the harness passes near exhaust manifolds or brackets. A visual inspection and a wiggle test with the multimeter connected can catch intermittent breaks.
Reluctor ring damage: A cracked, chipped, or missing tooth on the tone ring inside the engine will produce an erratic or missing signal even with a good sensor. This typically requires a scope to confirm, but sometimes visible through the sensor hole with a borescope.
Air gap too large: The sensor should sit very close to the reluctor ring (usually 0.020–0.060 inches). A loose mounting bracket or wrong spacer can push the sensor too far away.
ECM issues: Rare, but a damaged ECM input circuit can fail to read a perfectly good signal.

What Are the Most Common Mistakes When Diagnosing P0335?

After working through dozens of P0335 cases, these errors come up again and again:

Replacing the sensor without testing it first. Parts stores love to sell you a sensor, but more than half the time the sensor itself is fine.
Testing resistance on a hall-effect sensor. Resistance testing is only meaningful for magnetic sensors. Hall-effect sensors need voltage and reference voltage checks.
Forgetting to check the connector. A sensor can test perfect on the bench but fail in the vehicle because the connector isn't fully seated or the pins are corroded.
Not clearing the code after the repair. P0335 can remain stored as a history code even after the fix. Clear it and drive the vehicle through two or three complete drive cycles to see if it returns.
Ignoring related codes. If P0335 shows up alongside P0340 (camshaft sensor), the problem might be a shared ground, power supply, or timing chain issue affecting both signals.

What Should I Do After Testing?

Here's a practical sequence to move from diagnosis to repair:

Record your readings. Write down resistance, AC voltage output (for magnetic), or reference voltage (for hall-effect). Compare them to the published spec for your exact vehicle.
If the sensor failed testing, replace it with an OEM or high-quality equivalent. Cheap aftermarket sensors have a higher failure rate out of the box.
If the sensor tested good, inspect and repair wiring and connectors. Pay special attention to the ground circuit a bad ground mimics a failed sensor.
Clear the code with an OBD-II scanner.
Test drive the vehicle through at least two full drive cycles and recheck for codes.
If the code returns, consider checking the reluctor ring and timing chain condition, or have a shop perform an oscilloscope test to see the actual waveform.

Quick-Reference Checklist for P0335 Diagnosis

✅ Identify your sensor type (magnetic 2-wire vs. hall-effect 3-wire)
✅ Disconnect the sensor and test resistance (magnetic only)
✅ Test AC voltage output while cranking (magnetic) or reference voltage + signal (hall-effect)
✅ Inspect connector pins for corrosion and damage
✅ Check wiring harness for breaks, chafing, and shorts
✅ Verify the sensor mounting and air gap
✅ Replace the sensor only if testing confirms failure
✅ Clear the code and verify the fix with a drive cycle test

The P0335 code points you in a direction, but it doesn't hand you the answer. Voltage and resistance readings do. Test before you replace, check the wiring and connector before you blame the sensor, and work through the steps methodically. That approach saves time, money, and the frustration of fixing the wrong thing twice.