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P0654 — Engine Rpm Output Circuitopen

Generic OBD-II · all makesPowertrain (engine & transmission)

The engine computer (PCM) has detected an open circuit in the electrical path used to send the engine RPM signal to another component, such as the instrument cluster. This indicates that the signal is being interrupted by a break in the wiring or a disconnected terminal.

Symptoms

What causes it — most likely first

1. Damaged wiring

Frayed, broken, or rodent-damaged wires in the RPM output circuit.

2. Corroded connectors

Moisture or oxidation at the harness connectors preventing electrical continuity.

3. Loose terminal pins

A connector pin may have backed out of the housing or is not seated properly.

4. Faulty receiving module

Internal failure of the instrument cluster or secondary control module that receives the signal.

5. PCM internal failure

A failure of the output driver circuit within the engine computer.

How it's diagnosed

  1. Perform a full system scan to identify any accompanying fault codes.
  2. Visually inspect the wiring harness for obvious breaks, burns, or abrasions.
  3. Inspect all related connectors for corrosion, moisture, or bent pins.
  4. Measure the resistance of the RPM output circuit from the PCM to the receiving module to check for continuity.
  5. Use a multimeter or oscilloscope to verify if the PCM is generating the output signal.
  6. Test the receiving component (e.g., instrument cluster) for internal shorts or opens.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationSAE generic — identical on every make
Related codesP0650 — Mil Control CircuitopenP0651 — Sensor Reference Voltage B CircuitopenP0652 — Sensor Reference Voltage B Circuit LowP0653 — Sensor Reference Voltage B Circuit HigP0655 — Engine Hot Lamp Output Control CircuitP0656 — Fuel Level Output Circuit

Frequently asked

Does this code mean my crankshaft position sensor is bad?

Not necessarily. P0654 refers to the output circuit from the PCM to another device, whereas the crankshaft sensor is an input to the PCM.

Should I replace the PCM if I have this code?

No. Most P0654 faults are caused by wiring or connector issues. The PCM should only be replaced after the entire wiring harness has been verified as intact.

Will my car stop running if this circuit is open?

The vehicle will typically continue to run, although the tachometer may be non-functional and some accessory systems may enter a fail-safe mode.