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2009 GMC Acadia P0192, P0191, P0087 Fault Diagnosis After Head Gasket Repair

Model: 2009 Acadia Fault Code: P0087 Posted: 2022-01-02 13:58

I own a 2009 GMC Acadia with a 3.6L engine and recently experienced overheating issues that led to a head gasket failure. The cylinder heads were replaced, and the head gasket along with timing components were reinstalled during the motor removal process. After reassembly, the vehicle began displaying multiple diagnostic trouble codes: P0192 (Low Front Rail Pressure Sensor Voltage), P0191 (Front Rail Pressure Sensor Failure), P0087 (Fuel Rail Pressure Low), and P050A (Cold Start Idle Failure). The engine starts but exhibits erratic idle behavior with a strong fuel smell from the exhaust for approximately 10 minutes. After this period, the idle stabilizes and the P050A code clears, being replaced by P0089 (Fuel Pressure Regulator Failure). I'm seeking guidance on how to properly diagnose these issues. Given that this is a GDI engine with high-pressure fuel pump system, I believe the problem may be related to fuel pressure regulation or sensor malfunctions. However, without proper diagnostic tools and data analysis, it's difficult to pinpoint the root cause. Any advice on next steps—such as fuel pressure testing, sensor evaluation, or circuit checks—would be greatly appreciated.

Related fault codes
P0087P0191P0192
Comments (4)
Anonymous 2022-01-03 10:51

This vehicle has a GDI (Gasoline Direct Injection) system. Without a dedicated scan tool capable of monitoring real-time fuel pressure data, stored fault flags (STFT/LTFT), and sensor inputs, accurate diagnosis is extremely challenging.

Anonymous 2022-01-03 10:57

The 2009 Acadia uses a 3.6L engine with a high-pressure fuel pump. Unfortunately, I don’t have access to a scan tool that can perform the required diagnostic tests for this system.

Anonymous 2022-01-03 11:22

For GDI engines like this one, a high-quality scan tool is essential—capable of reading real-time fuel pressure, STFT (Short-Term Fuel Trims), and LTFT (Long-Term Fuel Trims). There are also functional tests specific to GDI systems that can help identify issues. I recommend finding an ASE-certified shop and scheduling a diagnostic session for 1–2 hours. Replacing parts without proper diagnostics may only address symptoms, not root causes. Common issues include wiring faults or connector problems. A comprehensive diagnosis requires scan tools, lab-grade oscilloscopes, accurate schematics, and in-depth understanding of engine operation. I’d suggest analyzing the enabling criteria of these codes and performing circuit checks to identify faulty components. I wish I could offer more direct help—let me know if you have any diagnostic equipment or meters available.

Anonymous 2022-01-03 11:25

A practical next step would be to test the fuel rail pressure sensor (FRP) directly, either by replacing it with a known-good unit or performing circuit continuity checks. This could help isolate whether the issue stems from the sensor itself or downstream components.