P0320
Ignition/Distributor Engine Speed Input Circuit MalfunctionP0320 is a generic OBD-II powertrain diagnostic trouble code: Ignition/Distributor Engine Speed Input Circuit Malfunction. It is logged by the engine control unit when the misfire monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0320 means
P0320 — "Ignition/Distributor Engine Speed Input Circuit Malfunction" — is stored when the PCM detects that the engine speed signal derived from the crankshaft position (CKP) sensor or distributor pickup has fallen outside its expected operating parameters. The engine speed input is used by the PCM to calculate ignition timing, fuel injection pulse width, and rev-limiter enforcement. Without a valid signal, the PCM cannot correctly manage combustion events.
P0320 is a general circuit malfunction code, meaning the signal is absent or grossly out of range rather than merely intermittent (see P0323 for the intermittent variant). It should be distinguished from the P0335 family, which are specific crankshaft position sensor circuit codes — P0320 historically targeted distributors and ignition-module-based speed pickups found on older and some import platforms, but on modern direct-fire systems it maps to the same CKP input circuit. When persistent, the engine may enter limp mode or fail to start entirely, as the PCM cannot confirm correct crank position.
Common causes include wiring faults, a failed sensor, voltage reference problems, or PCM input circuit damage. Oscilloscope testing of the sensor signal during cranking is the most reliable way to isolate the fault. Timing belt or chain slip can also trigger the code by displacing the sensor target relative to the sensor, so mechanical timing should be verified when the code accompanies other symptoms such as cam timing faults.
Common causes
Most-frequently reported root causes when P0320 is logged.
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1
Failed crankshaft position sensor or distributor speed pickup with degraded internal coil or lost reluctor-ring magnetization.
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2
Open circuit, short to ground, or short to voltage in the CKP/distributor sensor wiring harness.
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3
Corroded, loose, or damaged connector at the sensor or at the PCM pin.
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4
Loss of the 5V reference voltage supply to the sensor due to a blown fuse, faulty relay, or PCM reference circuit fault.
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5
Poor or broken engine ground strap causing signal reference instability.
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6
Timing belt or chain slip displacing the sensor trigger wheel position, producing out-of-range pulse timing.
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7
PCM input circuit failure — cracked solder joint, moisture intrusion, or component damage on the engine speed input stage.
Symptoms drivers notice
How to diagnose P0320
A typical diagnostic flow when this code is present.
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1
Retrieve all codes with a scan tool; note any concurrent cam sensor (P0340/P0345) or crankshaft sensor (P0335) codes that indicate a broader position sensor system fault.
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2
Inspect the CKP sensor or distributor pickup connector and wiring harness for corrosion, chafing, broken pins, or water intrusion.
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3
Verify 5V reference and ground integrity at the sensor connector with a digital multimeter; reference should read 4.8–5.2V with ignition on.
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4
Perform a continuity check on the signal wire from sensor to PCM with the connector unplugged to identify any open circuit.
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5
Test the sensor signal waveform with an oscilloscope during cranking — a healthy CKP signal should produce a clean, consistent square or sine wave with the expected tooth-gap dropout.
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6
Inspect the reluctor ring (tone wheel) on the crankshaft for missing, bent, or damaged teeth.
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7
Verify mechanical timing (belt/chain) is in specification, especially if cam-timing codes are also present.
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8
Replace the CKP sensor if signal output fails tests; retest before condemning the PCM.
Related powertrain codes
Frequently asked questions
What is the difference between P0320 and P0335?
P0335 specifically indicates a crankshaft position sensor circuit fault. P0320 is the older, broader "ignition/distributor engine speed input circuit" code that applies to any engine speed signal source, including distributor pickups on older engines. On modern direct-fire engines they often point to the same circuit, but P0335 is more specific to the CKP sensor itself.
Can P0320 cause a no-start?
Yes. If the engine speed signal is completely absent, the PCM cannot confirm crank position and will typically withhold spark and/or fuel, resulting in a crank-no-start condition. An intermittent loss may cause stalling or hard starting rather than a complete no-start.
Is P0320 related to ignition coil failure?
Not directly. P0320 is about the engine speed input circuit that the PCM uses to determine when to fire coils, not about coil output itself. However, if ignition events are disrupted due to an engine speed signal fault, the engine may run as if misfiring.
How do I know if my crankshaft position sensor is the cause of P0320?
After ruling out wiring faults, use an oscilloscope to observe the sensor signal during cranking. A healthy sensor produces a clean waveform with an identifiable reference gap. A flat or erratic trace points to a failed sensor. Swapping in a known-good sensor and retesting confirms the diagnosis.
Disabling P0320 in software
RaceTune can permanently disable P0320 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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