ECM Codes P0178?

TDCHRYSLER

MEMBER
2014 BUICK LA CROSSE
3.6L
V6
AUTOMATIC
130,000 MILES

Originally, I had my car scanned and received the codes 'P0178-00 Fuel Composition Sensor Circuit Low Frequency' and 'P2119-00 Throttle Closed Position Performance'. I changed the throttle body, cleared the codes and the engine light came off. Unfortunately, once I drove the car and rescanned, the engine light came back on, and the code was 'P0178-00 Fuel Composition Sensor Circuit Low Frequency'.

I also began to notice when I would go to the gas station for fuel, if I would open the tank cover before turning off, it has a rough idle/drag to turn off. Once I'm done getting the fuel and go to start the car there would be a drag/rough start. This has never happened before. I have even noticed a slight change in my fuel efficiency.

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
48,313 POSTS

So this can be caused by a weak primary fuel pump which makes sense since the car is hard starting at times.

P0178 - Fuel Composition Sensor Circuit Low Input

The circuit is low due to the low pressure. Here is how to check the primary fuel pressure to help confirm the issue. Verify the fuel pressure is between 345-690 kPa (50-100 psi) with the fuel pump running.

Check out the images (below). Please let us know what happens.

Images (Click to make bigger)

ECM Codes P0178?

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