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Hino P0524 Fault Code: Engine Oil Pressure Too Low

09/01/2026

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Technical Description

A drop-in engine oil pressure is sensed by the oil pressure switch.

Description Of Malfunction

Drop in engine oil pressure is detected.

DTC Set Condition

Check Conditions:

While the engine is in operation – Always.

Judgment Criteria:

The oil pressure switch continues to be ON for more than 30 seconds.

Reset Condition

Immediately after normal operation is restored.

Indication, Warning Or System Control Regulation When The DTC Is Set

− MIL: OFF

− SVS light: ON

− Engine output is restricted.

− Cruise control is not available.

− Engine shuts down in models for PTL or models with customized shutdown function.

Symptoms On The Vehicle When The Dtc Is Set

Symptoms on the Vehicle Due to Backup Control (Fail Safe

Function):

− Engine output is insufficient.

− Cruise control does not work.

− Engine is shut down in models with customized shutdown function.

Symptoms on the Vehicle Due to Malfunction:

Drop in engine oil pressure.

Pre – Inspection Work

Check that the battery voltage is in the normal range.

After – Inspection Work

− Clear all past DTCs.

− Check that no DTC is stored after test drive.

Possible Causes

− Drop in oil pan oil quantity: Drop in pressure due to air suction.

− Malfunction of oil pressure circuit: Drop in pressure due to oil leakage.

− Malfunction of oil pressure switch: Correct oil pressure cannot be sensed.

− GND short-circuit of harness: The sensing result of the oil pressure switch becomes invalid.

Inspection Procedure

Troubleshooting Steps

Step 1) Check the engine oil level.

Check the oil level gauge and make sure the engine oil quantity is within the stipulated value.
Check the engine oil condition (dirt, viscosity).

Were any failures found?

Yes – Adjust the engine oil quantity so that it is within the stipulated value.

Change the oil if it is dirty.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Go to Step 2.

Step 2) Check for engine oil leaks.

Make sure there is no oil leaking from the engine unit or from around the oil pressure switch.

Were any failures found?

Yes – Repair the faulty part.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Go to Step 3.

Step 3) Inspect the oil pressure switch connector.

Check the connection of the oil pressure switch connector (Looseness and poor contact).

Yes – Connect securely, repair if needed.

Clear all past DTCs. Check that no DTC is detected after test drive.

No – Go to Step 4.

Step 4) Inspect the oil pressure switch unit.

Set the starter switch to the “LOCK” position.
Disconnect the oil pressure switch connector.
Use the electrical tester to measure the resistance between the terminals of the oil pressure switch and ground.

MEASUREMENT CONDITIONS

STANDARD VALUES

Stop the engine (OFF)

Start the engine (ON)

With engine stopped: Less than 1 Ω

With engine running: ∞ Ω

Do the measurements meet the standard value?

Yes – Go to Step 5.

No – Replace the oil pressure switch.

Clear all past DTCs. Check that no DTC is detected after test drive.

Step 5) Inspect for short-circuit of the oil pressure switch harness.

Set the starter switch to the “LOCK” position.
Connect the signal check harness to the engine ECU vehicle-side harness. (Do not connect the

harness to the ECU).

Disconnect the oil pressure switch connector.
Use the electrical tester to measure the resistance between the OLSW (E41) terminal in the engine ECU (signal check harness) and ground.

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch:

LOCK

Engine ECU (signal check harness)

OLSW(E41) – Ground

∞ Ω

Do the measurements meet the standard value?

Yes – Go to Step 6.

No – Repair or replace the harness.

Clear all past DTCs. Check that no DTC is detected after test drive.

Step 6) Inspect disconnection of the oil pressure switch harness.

Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness) and oil pressure switch vehicle-side connector.

MEASUREMENT CONDITIONS

TESTER CONNECTIONS

STANDARD VALUES

Starter switch:

LOCK

Engine ECU (signal check

harness) – Oil pressure switch vehicle-side connector

OLSW(E41) – OIL(E2R)

Less than 1 Ω