2018 Cadillac CTS 2.0T P128A Fuel Pressure Sensor Performance

Question

My 2018 CTS is throwing a P128A code and occasionally lagging when I try to accelerate from a stop. The idle feels a bit rough when the engine is warm, but it doesn't seem to stall out completely. I am worried the high-pressure fuel pump might be failing since it sounds a bit louder than usual lately.

Jordan Lee · Accepted Answer

The issue ended up being the High Pressure Fuel Sensor located on the fuel rail, GM Part No. 12668351. I replaced the sensor and the short jumper harness that connects to it, as the pins showed signs of fretting corrosion. After clearing the codes and performing a fuel trim reset, the P128A stayed off and the car pulls smoothly again. The sensor was about $75 and took 45 minutes to install after letting the fuel system pressure bleed down.

torque_terry · Answer

This code is often triggered by a software logic error in the ECM. Check for any TSBs regarding ECM updates for the LTG engine; sometimes a reflash relaxes the diagnostic window for that pressure sensor to prevent nuisance codes.

Carlos Diaz · Answer

Start by checking the low-side fuel pressure using a mechanical gauge if possible. If the lift pump in the tank isn't providing steady pressure, the high-pressure sensor will report performance issues because it isn't getting enough volume to compress.

Dave Kowalski · Answer

Inspect the wiring harness near the back of the cylinder head. These looms are known to chafe against the heat shield, which can cause intermittent signal drops on the 5V reference circuit shared by the fuel pressure sensor.

2018 Cadillac CTS 2.0T P128A Fuel Pressure Sensor Performance

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