Hino P0088 Fault Code: Excessive Common-Rail Pressure
Technical description
- Common rail pressure is controlled by a discharge quantity of the supply pump
- Discharge quantity of the supply pump is adjusted by the SCV (suction control valve)
Description of malfunction
Abnormally high fuel pressure inside common rail is detected
Dtc set condition
DTC Detection Condition:
- Engine speed of 700 r/min or more
- The fuel injection quantity is 10 mm3/st. cyl or more
- A change in fuel injection quantity is less than 1.7 mm3/st. cyl
- SCV amperage reading is 1,500 mA or higher
- No DTCs related to supply pump
Judgment Criteria:
A calculated value of (actual common rail pressure reading – Target common rail pressure) remains at 15 MPa or greater for 15 seconds
RESET CONDITION
After normal operation is restored and the starter switch is on the “LOCK” position
Indication, warning or system control regulation when the dtc is set
- MIL: OFF
- SVS light: OFF
- Engine output is restricted
- Cruise control function is not available
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
Symptoms on the Vehicle Due to Malfunction:
Cruise control does not work
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
- Pre-fuel filter: Clogging
- Common rail pressure sensor:
- Irregular contact (fault in power supply, fault in GND).
- Fault in sensor
- Supply pump:
- Fault in SCV
- Fault in learned value.
- Common rail: Pressure limiter opening valve
- Harness related:
- Irregular contact of crankshaft position sensor and camshaft position sensor
- Misconnection
Inspection procedure
Troubleshooting steps
Step 1: Inspect the start of the engine
Did the engine start?
| Yes | Go to Step 4 |
| No | Go to Step 2 |
Step 2: Inspect the supply pump
Check if fuel is leaking or seeping out of the supply pump
Were any failures found?
| Yes | Replace the supply pump and go to Step 4 |
| No | Go to Step 3 |
Step 3: Function check of supply pump [Diagnostic Tool]
- Connect the vehicle to the diagnostic tool
- Set the starter switch to the “ON” position
- Select [Engine].
- Select [Actual common rail pressure] and [Target common rail pressure] in [Data monitor setting]
- Start the engine while checking the common rail pressure
| STANDARD VALUES |
| The actual common rail pressure rises and stabilizes at a constant value |
Were any failures found?
| Yes | Replace the supply pump and go to Step 4 |
| No | Go to Step 4 |
Step 4: Check the engine ECU
- Check the engine ECU software part number (ECU part number) by the diagnostic tool
- Confirm the latest part number with the OEM
Does the engine ECU have the latest software number?
| Yes | Go to Step 5 |
| No | Reprogram the engine ECU by using the diagnostic tool and then go to Step 5 |
Step 5: Inspect the fuel filter
- Check the fuel filter.
- Has the replacement period expired?
- Is it dirty, damaged, or clogged?
- Is it a genuine OEM part?
- Check if the fuel inside the fuel filter is within the standard value
| MEASUREMENT CONDITIONS | STANDARD VALUES |
| While engine is running | At least 25.4 mm {1 in.} above collar and below the element upper level. High-sped idle ≥ wide open throttle. Fuel level does not continue to drop during wide open throttle. |
Were any failures found?
| Yes | Replace the pre-fuel filter element and go to Step 6 |
| No | Go to Step 11 |
Step 6: Inspect the fuel pipe
- Check if the fuel pipe and hose between the fuel tank and pre-fuel filter are clogged, punctured, or bent
- Make sure the fuel pipe joint bolts are not loose
Were any failures found?
| Yes | Repair or replace the faulty part and go to Step 7 |
| No | Go to Step 7 |
Step 7: Inspect the fuel tank breather
- Check if the breather hose is clogged, punctured, or bent
- Make sure the check valve is functioning normally.
Were any failures found?
| Yes | Repair or replace the faulty part and go to Step 8 |
| No | Go to Step 8 |
Step 8: Inspect the fuel tank feed pipe
Make sure the fuel tank feed pipe is not clogging
Were any failures found?
| Yes | Repair or replace the faulty part and, go to Step 9 |
| No | Go to Step 9 |
Step 9: Inspect the fuel tank
Drain fuel out of the fuel tank and check if there are foreign objects inside the tank
| Yes | Remove the foreign object and clean the fuel tank. Then go to Step 10 |
| No | Go to Step 10 |
Step 10: Inspect the supply pump gauze filter
Make sure the gauze filter (built into the supply pump) is not clogged
Were any failures found?
| Yes | Clean the gauze filter and go to Step 11 |
| No | Go to Step 11 |
Step 11: Inspect the fuel high-pressure pipe
Make sure the fuel high-pressure pipe is not leaking fuel
Were any failures found?
| Yes | Repair or replace the faulty part and go to Step 12 |
| No | Go to Step 12 |
Step 12: Inspect the fuel filter
Make sure the fuel filter is not clogging
Were any failures found?
| Yes | Repair or replace the faulty part and go to Step 13 |
| No | Go to Step 13 |
Step 13: Inspect the SCV connector
Check the connection of the SCV connector (Looseness and poor contact)
Were any failures found?
| Yes | Repair or replace the faulty part and go to Step 14 |
| No | Go to Step 14 |
Step 14: Inspect the common rail pressure sensor connector.
Check the connection of the common rail pressure sensor connector (Looseness and poor contact)
Were any failures found?
| Yes | Repair or replace the faulty part and go to Step 15 |
| No | Go to Step 15 |
Step 15: Inspect the common rail pressure sensor power supply.
- Disconnect the common rail pressure sensor connector
- Set the starter switch to the “ON” position
- Use the electrical tester to measure the voltage between the terminals of the common rail pressure sensor vehicle-side connector
| MEASUREMENT CONDITIONS | TESTER CONNECTIONS | STANDARD VALUES |
| Starter switch: ON | Common rail pressure sensor vehicle- side connector
VCC1 – GND1 VCC2 – GND2 |
4.5 – 5.5 V |
Do the measurements meet the standard value?
| Yes | Go to Step 16 |
| No | Replace the common rail pressure sensor and then go to Step 16 |
Step 16: Inspect the crankshaft position sensor (engine speed main sensor) [Diagnostic Tool]
- Set the starter switch to the “ON” position.
- Select [Engine].
- Select [NE Active identification], [G Active identification] in [Data monitor setting].
- Start the engine and confirm that the engine main speed sensor (NE) and sub speed sensor (G) operate (stay ON) continuously.
Were any failures found?
| Yes | Check the faulty the crankshaft position sensor (engine speed main sensor) and repair or replace it as needed. After inspection, go to Step 17 |
| No | Go to Step 17 |
Step 17: Inspect the fuel return pipe and hose
Check if the fuel return pipe and hose are clogged
Were any failures found?
| Yes | Repair or replace the faulty part. Clear all past DTCs. Check that no DTC is detected after test drive |
| No | Procedure completed. Clear all past DTCs. Check that no DTC is detected after test drive |
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