2018 Cadillac CTS 2.0L P128A Fuel Pressure Sensor Performance issue

Question

My Cadillac started throwing a P128A code suddenly and feels a bit sluggish when merging onto the highway. Idle seems fine, but the live data shows the fuel pressure sensor readings jumping around erratically between 400 and 800 psi at idle. I am worried the high-pressure pump might be failing.

fleet_chief_42 · Accepted Answer

The issue ended up being a faulty Fuel Rail Pressure Sensor (Part #12668353). I replaced the sensor and the intermittent P128A code has not returned in over 500 miles. Note that you need a 27mm deep socket to get the old one off, and it is vital to torque it to 24 lb-ft to prevent leaks. The sensor cost about $85 from the dealer and took about 30 minutes to swap out after relieving the fuel system pressure.

Pete Sanders · Answer

Have you logged the high-pressure fuel pump (HPFP) desired vs actual pressure? If 'actual' cannot keep up with 'desired' during a wide-open throttle pull, you likely have a failing HPFP or a worn camshaft lobe.

obd2_owl · Answer

Check the wiring harness near the back of the cylinder head. These LTG engines are known for vibration causing the fuel pressure sensor wires to rub against the heat shield, which can cause intermittent signal drops.

Luis Hernandez · Answer

Before replacing parts, check if there is an ECM software update. GM released several bulletins regarding fuel pressure sensor diagnostics and threshold adjustments for the 2.0L and 3.6L engines to prevent nuisance codes.

2018 Cadillac CTS 2.0L P128A Fuel Pressure Sensor Performance issue

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