08-08-2025, 07:47 PM
Understanding the Fault and When It Occurs
An EW145B operator in Pakistan experiences repeated engine shutdowns shortly after starting the machine. Initial scans reveal ECU fault codes 128-232-4 and 128-97-7. Voltage readings on the sensor reference drop below the required 5 V, and the rail pressure remains abnormally high—indicating a stuck relief valve and shorted sensor line. After replacing the faulty sensor and repairing the wiring short, the machine runs smoothly without shutdowns.
Why This Matters
- On the Volvo EW145B excavator, operators report a critical “Stop Engine” message appearing soon after startup, causing the machine to shut down within 30 to 60 seconds.
- Diagnostic readouts show fault codes like 128 SID 232-4 (ECU error) and occasionally 128 PSID 97-7, pointing toward internal sensors or communication issues.
- 128‑232‑4 means that the engine control unit (E‑ECU) has detected a voltage drop below 4.5 V on reference lines EA7/EA11—suggesting that the rail pressure sensor’s 5 V reference may be shorted to ground.
- 128‑97‑7 indicates that the rail pressure relief valve is stuck closed, likely because the ECU cannot read pressure when the sensor circuit is compromised.
- E-ECU (Engine Electronic Control Unit): The central processor coordinating engine systems; critical for detecting voltage and pressure anomalies.
- Rail Pressure Sensor & 5 V Reference Line: The sensor monitors fuel rail pressure and relies on a stable 5 V reference supplied by the ECU. A short here throws the readings off.
- Relief Valve: The mechanism that regulates excessive pressure in the fuel rail—its failure to open disrupts engine operation.
- PSID Code: Volvo’s proprietary identifier indicating specific system-level component faults.
- Begin by connecting a diagnostic tool (like Volvo’s service scan) to extract stored fault codes promptly after startup—before the shutdown message appears.
- Use service mode to monitor rail pressure and voltage readings in real time. A dropping 5 V reference or erratic pressure behavior confirms sensor or wiring issues.
- Inspect and test wiring harnesses for ground shorts, loose connectors, or physical damage. Replace or repair as needed.
- Force a test of the rail pressure relief valve and ensure it actuates properly—clean or replace if stuck.
An EW145B operator in Pakistan experiences repeated engine shutdowns shortly after starting the machine. Initial scans reveal ECU fault codes 128-232-4 and 128-97-7. Voltage readings on the sensor reference drop below the required 5 V, and the rail pressure remains abnormally high—indicating a stuck relief valve and shorted sensor line. After replacing the faulty sensor and repairing the wiring short, the machine runs smoothly without shutdowns.
Why This Matters
- These faults trigger immediate engine shutdowns to prevent catastrophic damage—such as fuel system failures or engine seizure.
- Swift diagnosis based on accurate codes allows operators to resume work with minimal downtime and avoid costly repairs.
- Recognizing that ECU codes like SID and PSID provide direct guidance to problematic components empowers efficient troubleshooting.
- The Volvo EW145B “Stop Engine” fault is typically tied to the ECU detecting rail pressure sensor anomalies or voltage reference failures.
- Codes 128‑232‑4 and 128‑97‑7 pinpoint issues with the sensor’s 5 V reference and relief valve operation.
- Effective resolution comes from real-time diagnostic testing, careful electrical inspection, and thorough component checks.
- Understanding this process can drastically reduce machine downtime and foster safer operations.
