P1174 Engine Code – Diagnosis & Troubleshooting

The P1174 engine fault code for Chevy and GMC vehicles reads “Fuel Trim Cylinder Balance Bank 1“. Additionally, you might see a P1175 code which represents the same problem but is related to Bank 2. But what does that mean and how do you fix it?

A P1174 & P1175 trouble code means that your air to fuel ratio is either running too lean or too rich. 

Engines will have two banks. In traditional V-shaped engines, the 2-4 cylinders (depending on whether it is a V4 or V8, etc.) on the left side are considered “Bank 1” and the cylinder on the left are considered “Bank 2”. Ultimately, whether you are getting a bank 1 or bank 2 error code is somewhat irrelevant as the underlying problems do not differ. They are differentiated because the two different banks sometimes have different sensors, etc.

These error codes are all too common on Chevy and GMC vehicles and can be caused by a number of different factors relating to both fueling and air.

Air-to-Fuel Ratios

A lean air to fuel ratio, or AFR, occurs when your engine is getting too little fuel compared to the amount of air it is getting. Inversely, a rich AFR occurs when you are getting too much fuel compared to the amount of air. Because an AFR is a ratio, the issue can be caused from both sides of the ratio. As an example, a rich AFR can occur because you have an intake air leak and aren’t getting enough air, or because your injectors are stuck open and you sending too much fuel.

Bad AFR ratios can cause a number of performance issues such as rough idling, sluggish or hunting acceleration, misfires, etc. Imbalances can lead to serious engine problems if an engine is run lean or rich for too long.

P1174 Fault Code Causes

As mentioned above, P1174 codes can come from sensors, the fueling system, or the intake system. On Chevy’s it is common for these codes to appear once a day, once a month, etc. and continually reappear even once being cleared with a code scanner. Here are the most common causes on Chevy’s:

• Bad O2 Oxygen Sensor
• Dirty or faulty MAF (mass air flow sensor)
• Faulty fuel injectors (either clogged, failed shut or open)

Fortunately, on Chevy and GMC cars, a faulty O2 sensor tends to be the most common cause. It also tends to be more common with folks who are running exhaust systems and intakes, or K&N drop-in filters.

Symptoms

Obviously, the “symptom” of this fault code is a check engine light that is reading P1174: Fuel Trim Cylinder Balance Bank 1. But, depending on what is causing the engine code, you might have various different performance and engine symptoms. Determining whether you have any of these can be helpful is diagnosing the cause.

• Rough idling
• Engine misfires
• Sluggish performance, acceleration, etc.
• Poor fuel economy / gas mileage

If you aren’t experiencing any engine or performance issues, you probably just had a bad sensor. A bad O2 sensor won’t necessarily have any negative engine effects with the exception of worse fuel economy. If you are experiencing idling/driving related issues then you probably have a vacuum leak (intake leak) or a fuel injector problem.

How to Fix a P1174 Engine Error Code

If you aren’t experiencing any engine performance issues or rough running, you likely have a bad O2 sensor. In this case, the fix is as simple as replacing your O2 sensor, which costs about $50 and can be DIY’d easily. After replacing your O2 sensor, if you continue to receive P1174 or P1175 engine codes, you should check your MAF and try cleaning or replacing that.

If you are having performance issues, you’ll need to do a little more diagnosing to determine if it’s being caused by the injectors or by an air leak.

DIY O2 Sensor Guide: https://www.1aauto.com/how-to-replace-o2-sensor-07-13-chevy-silverado/video/1401