P0320 Code: Ignition/Distributor Engine Speed Input Circuit

Quick answer

• What it means: The Powertrain Control Module (PCM) is not receiving a reliable engine speed signal (RPM) from the ignition or distributor engine speed input circuit.
• Severity: High. Your vehicle will likely stall unexpectedly or fail to start altogether. Get it towed to avoid being stranded.
• Most common cause: A failing crankshaft position sensor (CKP) or a faulty ignition distributor (on older vehicles).

What the P0320 code means

The official OBD-II definition for P0320 is "Ignition/Distributor Engine Speed Input Circuit."

In plain English, this means the computer that controls your engine (the PCM) has lost track of how fast the engine is spinning. The PCM relies on a continuous engine speed signal (RPM data) to properly time the spark plugs and fuel injectors. Depending on the make and model of your vehicle, this signal comes from the crankshaft position sensor, the camshaft position sensor, or the distributor.

When the PCM detects an interruption, inconsistency, or complete absence of this signal while the engine is running or cranking, it triggers the P0320 code. Without knowing the exact position and speed of the engine components, the computer cannot calculate the correct fuel delivery or ignition timing.

Common symptoms

Because this sensor data is critical to keeping the engine running, the symptoms are usually severe and highly noticeable:

• Check Engine Light is illuminated
• Engine stalling (especially when coming to a stop or at idle)
• Engine cranks but will not start (no-start condition)
• Hesitation, bucking, or surging while driving
• Engine misfires and rough idling
• Loss of engine power

Common causes

Ranked from most to least likely, the culprits behind a P0320 code include:

1. Defective Crankshaft Position Sensor (CKP): The most common failure point on modern distributor-less engines.
2. Defective Camshaft Position Sensor (CMP): Often works in tandem with the CKP; a failure here can trigger the speed input circuit code.
3. Worn or Faulty Distributor: On older vehicles, the pickup coil or Hall effect sensor inside the distributor can fail.
4. Wiring and Connector Issues: Corroded, loose, or chafed wires in the engine speed sensor circuit causing intermittent signal loss.
5. Weak Battery or Poor Grounds: Low system voltage can distort the sensor signal reaching the PCM.
6. Faulty Powertrain Control Module (PCM): Rare, but internal failure can cause it to misinterpret a good sensor signal.

How a technician diagnoses it

When an ASE-certified technician tackles a P0320, they follow a systematic approach to pinpoint the exact failure rather than just throwing a sensor at it:

1. Scan Tool Data & Freeze Frame: The tech connects an advanced scan tool to pull the code and read the freeze-frame data to see the engine conditions when the code set.
2. Live Data Monitoring (RPM PID): The technician will monitor the Engine Speed (RPM) parameter while cranking the engine. A healthy engine will show a steady 150–250 RPM during cranking. If the RPM reads "0" or jumps erratically while cranking, the PCM is definitely not getting a good signal.
3. Visual Inspection: Wiring harnesses running to the crank, cam, or distributor sensors are inspected for heat damage, oil contamination, or rodent damage. Connectors are checked for green corrosion.
4. Sensor Testing (Lab Scope): Using a digital oscilloscope, the technician taps into the signal wire.
   • For a Variable Reluctance (VR) sensor, they look for an alternating current (AC) sine wave that increases in amplitude with RPM.
   • For a Hall Effect sensor, they look for a crisp, clean 0-to-5V (or 0-to-12V) square wave. If the wave drops out, the sensor is faulty.
5. Circuit Testing: If the sensor produces a good wave, the tech uses a multimeter to check for high resistance, an open circuit, or a short to ground between the sensor connector and the PCM pins.

Typical repair cost

The cost to fix a P0320 depends largely on whether the issue is a sensor or a wiring problem. Here are the typical parts and labor ranges:

• Crankshaft or Camshaft Position Sensor Replacement: $150 – $350
• Ignition Distributor Replacement (Older Vehicles): $200 – $500
• Wiring Repair: $100 – $250 (varies based on diagnostic time and wire location)
• Ignition Module Replacement: $150 – $400

Note: These estimates include parts and labor at a typical independent repair facility.

Can I keep driving with this code?

No. It is highly recommended that you do not drive with a P0320 code.

Because this code indicates a breakdown in the primary ignition timing signal, your vehicle is a prime candidate for sudden stalling in traffic, which can be incredibly dangerous and lead to an accident. In many cases, once you turn the car off, the no-start condition will leave you stranded. Have the vehicle towed to a repair shop.

Related codes

You will often see P0320 paired with other ignition and timing codes, including:

• P0335: Crankshaft Position Sensor "A" Circuit
• P0340: Camshaft Position Sensor "A" Circuit
• P0300: Random/Multiple Cylinder Misfire Detected
• P0321: Ignition/Distributor Engine Speed Input Circuit Range/Performance
• P0322: Ignition/Distributor Engine Speed Input Circuit No Signal

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