If your check engine light is on and a scan tool shows P1019, you’re not seeing a generic OBD2 code it’s a manufacturer-specific trouble code used by Honda and Acura. Unlike codes like P0300 or P0420, P1019 doesn’t appear in standard SAE definitions. It’s tied to the engine oil pressure switch circuit, and misreading it can send you down the wrong repair path like replacing an oil pump when the real issue is a broken wire or corroded connector.

What does P1019 actually mean?

P1019 stands for “Engine Oil Pressure Switch Circuit Low Voltage” in Honda and Acura vehicles. It means the powertrain control module (PCM) detected abnormally low voltage from the oil pressure switch usually under 0.5 volts when the engine is running. This isn’t necessarily about low oil pressure itself; it’s about the signal the PCM receives from the switch. The switch is normally open until oil pressure reaches ~6–8 psi, then it closes and grounds the circuit. If the PCM sees constant low voltage, it assumes either the switch is stuck closed, the circuit is shorted to ground, or there’s a wiring fault.

What symptoms go with P1019?

You’ll likely see one or more of these:

  • The check engine light stays on (no blinking or stalling)
  • No oil pressure warning light on the dash that’s separate and often not triggered by P1019
  • No drivability issues: no rough idle, hesitation, or loss of power
  • Oil level and condition look normal during inspection

That last point matters: if the engine runs fine and oil is clean and at the right level, P1019 is almost certainly an electrical issue not mechanical. Jumping straight to oil pump replacement is a common mistake we see in troubleshooting guides for mechanics.

Where is the oil pressure switch located?

On most Honda 4-cylinder engines (like the R18 or K24), it’s threaded into the cylinder block near the oil filter housing often behind the alternator or tucked beside the exhaust manifold. On V6 models (like the J35), it’s typically on the front timing cover. Access varies, but it’s rarely buried deep. Before pulling anything, inspect the connector first: corrosion, bent pins, or moisture are frequent culprits.

What causes P1019 and what doesn’t?

Real causes include:

  • A damaged or shorted wire between the switch and PCM (especially near heat sources or sharp edges)
  • A failed oil pressure switch (internal short to ground)
  • Corrosion or loose fit in the switch connector
  • Rarely: a faulty PCM (only after ruling out all wiring and switch issues)

What doesn’t cause P1019:

  • Low oil level (that usually sets P2159 or triggers the oil light)
  • Clogged oil filter or dirty oil (those affect actual pressure, not the switch circuit voltage)
  • Failing oil pump (again unless it somehow shorts the switch wiring, which is extremely unlikely)

For deeper diagnostics, technicians often reference the DTC meaning tailored for automotive technicians, including pinout diagrams and live-data expectations.

How to test the P1019 circuit yourself

You don’t need a lab scope, but you do need a multimeter and basic access:

  1. Turn the ignition to ON (engine off) and measure voltage at the switch connector’s power wire should be ~5V reference from the PCM
  2. Check continuity from the switch ground wire to the PCM connector (look for breaks or high resistance)
  3. Unplug the switch and measure resistance across its terminals should be infinite (open) when cold and unpowered
  4. With the engine running, monitor the signal wire voltage at the PCM end: it should drop to near 0V once oil pressure builds

If voltage stays low even with the switch unplugged, the short is in the harness not the switch. That’s a key detail covered in Honda-specific diagnostics resources.

Next step: verify before replacing

Before buying a new oil pressure switch or chasing wiring, do this quick verification:

  • Clear the code with a scanner
  • Start the engine and let it idle for 30 seconds
  • Rescan if P1019 returns immediately, the circuit fault is active
  • If it takes several drive cycles to return, the issue may be intermittent (often connector-related)

If you’re seeing P1019 on a 2006–2015 Civic, CR-V, or Accord, double-check the connector behind the alternator it’s a known wear point. And if you're using aftermarket gauges or oil cooler kits, inspect any spliced wires near the switch location.