Hino P0629 Fault Code: Suction Control Valve For Fuel Supply Pump – Circuit (Circuit High)

Technical Description

The supply pump controls a fuel delivery quantity to control common rail pressure.

Description Of Malfunction

Abnormal voltage of supply pump magnetic valve (suction control valve) is detected. Possible +B short.

DTC Set Condition

DTC Detection Condition:

• Starter switch ON.
• Battery voltage is in the range of 10 V to 16 V.
• The engine has stopped or runs at 500 r/min or higher.
• The injectors and injector driver circuits have started running.

The conditions described above remain for 5 seconds.

Judgment Criteria:

SCV (suction control valve) drive current remains less than 1,900 mA for 2.1 seconds.

Reset Condition

After restoration to normal condition and starter switch “OFF”.

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

• MIL: ON
• SVS light: OFF
• Engine output is restricted.
• Cruise control function is not available.
• Idling stop system is not available.
• PTO 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.
• Idling stop system does not work.
• PTO cannot be used.

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

• Harness disconnection or short-circuit.
• Looseness or poor contact of connector.
• Supply pump (SCV) unit failure.
• Engine ECU malfunction.

Inspection Procedure

Troubleshooting Steps

Step 1) Inspect the suction control valve (SCV) connector.

Check the connection of the suction control valve (SCV) connector (Looseness and poor contact).

Were any failures found?

Step 2) Inspect the suction control valve (SCV) unit.

1. Set the starter switch to the “LOCK” position.
2. Disconnect the SCV connector.
3. Use the electrical tester to measure the resistance between the terminals of the suction control valve.
4. Use the electrical tester to measure the resistance between the suction control valve terminal and ground.

Do the measurements meet the standard value?

Step 3) Inspect for short-circuit in wire harness of suction control valve.

1. Set the starter switch to the “LOCK” position.
2. Disconnect the engine ECU connector.
3. Use the electrical tester to measure the resistance between the suction control valve vehicle-side connector terminals and ground.

Do the measurements meet the standard value?

Step 4) Inspect for disconnection in wire harness of suction control valve.

1. Set the starter switch to the “LOCK” position.
2. Connect the SCV connector.
3. Connect the signal check harness to the engine ECU vehicle-side harness. (Do not connect the harness to the ECU).
4. Use the electrical tester to measure the resistance between the terminals of the engine ECU (signal check harness) terminals.

Do the measurements meet the standard value?

Step 5) Check the DTC detected (Engine ECU) [Diagnostic Tool].

1. Warm-up the engine. (Engine coolant temperature: 60°C {140°F} or more).
2. Stop the engine and set the starter switch to the “LOCK” position.
3. Connect the vehicle to the diagnostic tool.
4. Set the starter switch to the “ON” position.
5. Select [Engine] and check if the DTC P0628 or P0629 has been detected.

Has DTC P0628 or P0629 been detected?

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