P0320

Universal

Ignition/Distributor Engine Speed Input Circuit Malfunction

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

The engine control system has detected a problem in the circuit that supplies an engine-speed signal from the ignition or distributor system. This signal helps the system determine whether and how fast the engine is turning. Depending on the vehicle and the fault, the engine may be difficult to start, run poorly, stall, or show an inaccurate tachometer reading; some vehicles may have no noticeable symptoms.

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⚠️ Before You Begin (Safety First)

If the engine stalls, will not restart reliably, or runs so poorly that you cannot control the vehicle safely, stop driving and arrange a tow or professional diagnosis. An unexpected stall can be hazardous in traffic.

Common Symptoms

  • The engine may crank without starting if the control system cannot receive a usable engine-speed signal.
  • The engine may start and then stall, or stall while running, if the signal is intermittent or lost.
  • Starting may be difficult or the engine may run roughly if the speed signal is unreliable.
  • The tachometer may behave erratically or fail to show engine speed, depending on how the vehicle uses this circuit.
  • There may be no obvious symptoms if the fault is intermittent or does not significantly affect engine operation.

Common Causes

  • Damaged, loose, corroded, or poorly connected wiring or connectors in the engine-speed input circuit.
  • A fault in the applicable ignition or distributor engine-speed signal source.
  • A problem with circuit power or ground, where applicable to the vehicle design.
  • An intermittent signal caused by damaged wiring, a poor connection, or electrical interference.
  • A fault in the control module's input circuit, after the signal source and wiring have been checked.

Diagnostic Steps

  1. Check whether the engine starts and runs normally, and note any stalling, difficult starting, rough running, or tachometer irregularity. Stop driving if stalling makes the vehicle unsafe.
  2. With the engine off, visually inspect accessible ignition/distributor-related wiring and connectors for looseness, corrosion, chafing, or damage. Do not pull on wires or probe unidentified terminals.
  3. If a suitable scan tool is available, record this and any related codes and note whether engine speed appears in scan data while cranking. An absent or erratic reading can help guide diagnosis but does not identify a failed part by itself.
  4. Have the vehicle-specific circuit checked before replacing components, especially if the fault is intermittent or the visual inspection finds no problem.

When to Call a Professional

A technician can review related codes and scan data, check whether an engine-speed reading is present during cranking, and test the applicable circuit using vehicle-specific wiring information. Testing should distinguish a signal-source problem from wiring, connection, power or ground issues, and a control-module input problem before parts are replaced.

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Commonly Asked Questions

Does P0320 prove that the distributor or a sensor has failed?

No. It identifies a detected malfunction in the ignition/distributor engine-speed input circuit. Wiring, connectors, power or ground, the signal source, and the control-module input may all need to be considered.

Can a vehicle with P0320 still run?

It may run normally, run poorly, stall, or fail to start, depending on how the fault affects the engine-speed signal and the vehicle's design.

Is P0320 the same as a specific crankshaft or camshaft sensor code?

Not from this definition alone. The code describes an ignition/distributor engine-speed input circuit malfunction; the exact signal source and circuit layout depend on the vehicle.

What should be checked before replacing parts?

Check related codes and scan data, inspect accessible wiring and connectors, and test the applicable signal circuit using vehicle-specific service information.

Browse Available Code Guides

Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.