How to Troubleshoot P0335 Engine Speed Signal Missing

Your check engine light came on, you plugged in a scanner, and now you're staring at a P0335 code. The engine might be stalling, cranking without starting, or running rough. This fault means the engine control module (ECM) has lost the signal from the crankshaft position sensor and without that signal, your engine can't properly time its ignition or fuel injection. Getting to the bottom of this code quickly can save you from being stranded and prevent more expensive damage down the line.

What Does the P0335 Code Actually Mean?

P0335 stands for "Crankshaft Position Sensor 'A' Circuit Malfunction." The crankshaft position sensor (CKP sensor) monitors the position and rotational speed of the crankshaft. It sends this data called the engine speed signal to the ECM in real time. The ECM uses it to control ignition timing, fuel delivery, and variable valve timing.

When the ECM expects a signal from the CKP sensor and doesn't get one, or the signal is erratic, it sets the P0335 code. This doesn't always mean the sensor itself is bad. The problem could be in the wiring, the connector, the reluctor ring, or even the ECM itself.

What Are the Symptoms You Might Notice?

Before you grab your multimeter, it helps to know what symptoms often come with a P0335 code. Not every vehicle will show all of these, but here are the most common ones:

Engine won't start or has extended cranking time. Without the speed signal, the ECM can't time the spark.
Engine stalling at idle or while driving. A intermittent signal drop can cause sudden shutdowns.
Rough idle or misfires. Inconsistent readings throw off the firing order.
Reduced fuel economy. Poor timing leads to inefficient combustion.
Check engine light on with P0335 stored or pending.

Some vehicles will still run with a failing CKP sensor but will show degraded performance. Others won't start at all. The behavior depends on the make, model, and whether your engine uses a backup camshaft position sensor to approximate crankshaft timing. You can learn more about how P0335 shows up across different vehicle makes and models to get a better idea of what to expect from your specific car.

What Do You Need Before You Start Troubleshooting?

Having the right tools on hand makes this job much easier. Here's what you'll need:

OBD-II scanner to read, confirm, and clear codes.
Digital multimeter to test resistance, voltage, and signal output.
Wiring diagram for your specific vehicle pin locations and wire colors vary by manufacturer.
Basic hand tools sockets, ratchets, and screwdrivers to access the sensor.
Inspection mirror and flashlight CKP sensors are often tucked behind the engine near the crankshaft pulley or flywheel.

How Do You Troubleshoot P0335 Step by Step?

Start simple and work your way deeper. Replacing parts blindly wastes time and money.

Step 1: Scan and Record

Use your OBD-II scanner to read all stored and pending codes. Write them down. If there are companion codes like P0340 (camshaft position sensor circuit) that can point you toward a shared wiring issue or a timing chain problem. Clear the codes and see if P0335 returns after a short drive. If it comes back immediately, the fault is likely hard (not intermittent).

Step 2: Visually Inspect the Sensor and Wiring

Locate the crankshaft position sensor. On most vehicles, it sits near the crankshaft pulley, the harmonic balancer, or the transmission bell housing. Check for:

Cracked, corroded, or loose connector pins
Chafed, melted, or broken wires
Oil or debris contamination on or around the sensor
Signs of heat damage

A damaged wiring harness is one of the most overlooked causes. Wiggle the connector while the engine is running (carefully) and watch for changes in engine behavior or signal.

Step 3: Test the Sensor Resistance

Unplug the CKP sensor connector. Set your multimeter to measure resistance (ohms). Place the probes on the sensor terminals. Compare your reading to the manufacturer's specification this is typically between 200 and 1,500 ohms, depending on the sensor type (magnetic vs. Hall effect).

If the reading is open (OL) or near zero, the sensor is bad and needs replacement. For a more detailed walkthrough of sensor-specific testing, see this crankshaft position sensor diagnosis guide.

Step 4: Check for Power and Ground at the Connector

Reconnect the sensor and back-probe the connector with the ignition on (engine off). You should see a reference voltage (usually 5V or 12V, depending on design) on the signal or power wire, and a solid ground. No voltage means the problem is upstream possibly a damaged wire between the sensor and the ECM, a blown fuse, or a failing ECM.

Step 5: Test the Signal with a Multimeter or Oscilloscope

With the engine cranking (or running if it starts), check the signal wire for voltage fluctuation. A healthy CKP sensor generates an AC voltage signal (for magnetic types) or a switching digital signal (for Hall effect types). No signal or a flat line means the sensor or its circuit is dead.

An oscilloscope gives the clearest picture here. It lets you see the waveform pattern and spot issues like a damaged reluctor ring tooth that a multimeter might miss.

Step 6: Inspect the Reluctor Ring (Tone Ring)

The reluctor ring is the toothed wheel that spins past the CKP sensor. If a tooth is cracked, missing, or bent, the sensor will produce an erratic signal even if the sensor itself is fine. This is harder to check without removing the sensor or the crankshaft pulley, but it's a real cause that many people skip.

Step 7: Check the ECM and Related Circuits

If the sensor tests good, the wiring is intact, and the reluctor ring looks fine, the problem may be in the ECM. This is rare, but it happens especially on vehicles with known ECM issues or water intrusion. Before condemning the ECM, check all ground points and power feeds to the module. Corroded grounds are a surprisingly common root cause.

For a broader look at the full diagnostic process, the complete P0335 code diagnosis steps cover each stage in more detail.

What Are the Most Common Mistakes When Diagnosing P0335?

A few errors come up again and again in P0335 troubleshooting:

Replacing the sensor without testing it first. The sensor is often not the problem. Wiring faults are just as common.
Ignoring companion codes. A P0340 or P0336 can change the direction of your diagnosis.
Not checking the reluctor ring. A single damaged tooth can cause the exact same code.
Using the wrong replacement sensor. Magnetic and Hall effect sensors are not interchangeable. Using the wrong type gives no signal at all.
Skipping the wiring inspection. Rodent damage, heat shielding failures, and corroded connectors cause a large percentage of these faults.
Not clearing the code after repairs. The ECM may not immediately turn off the check engine light. Clear it and drive to confirm.

Can You Still Drive With a P0335 Code?

It depends on the severity. Some vehicles will enter limp mode and still move, but with reduced power and limited RPM. Others won't start at all. Either way, driving with a missing or unreliable engine speed signal is risky. You could lose power steering and brake assist if the engine stalls unexpectedly. Fix it before relying on the vehicle for daily driving.

How Much Does It Cost to Fix a P0335 Code?

Costs vary based on the root cause:

Crankshaft position sensor replacement: $20–$100 for the part, $50–$150 labor at most shops.
Wiring repair: $50–$300 depending on the extent of the damage and accessibility.
Reluctor ring replacement: $100–$500+ because it often requires partial disassembly.
ECM replacement or repair: $500–$1,500+. This is the last thing to check, not the first.

If you're doing the work yourself, a new CKP sensor and some wire repair supplies are usually under $100 total.

Troubleshooting Checklist for P0335

Read and record all fault codes with an OBD-II scanner.
Clear codes and confirm P0335 returns.
Visually inspect the CKP sensor, connector, and surrounding wiring for damage.
Measure sensor resistance and compare to the spec in your vehicle's service manual.
Check for reference voltage and ground at the sensor connector.
Test the sensor signal output during cranking or running.
Inspect the reluctor ring for missing or damaged teeth.
Verify all ECM grounds and power feeds are clean and tight.
Replace only the part that failed the test then clear codes and verify the repair.

Working through these steps in order keeps you from throwing parts at the problem. Start with what you can see and measure before assuming the worst.