![what does p0171 and p0174 ford engine codes mean what does p0171 and p0174 ford engine codes mean](https://www.carparts.com/blog/wp-content/uploads/2020/03/closeup-of-car-engine.jpeg)
If the fuel trim comes down chances are you have a vacuum leak. Raise engine to 2500 RPM’s, hold and re-check. Monitor your fuel trim at idle, if you engine is running lean your fuel trim is high. Short term fuel trim is also very good for diagnosing vacuum leaks. A weak MAF signal should not set a incorrect gear ration code, but it’s a very good thing to take note of in case you ever run into something like this again. It has something to do with the way the on-board computers operate. The part about the incorrect gear ration codes setting is only related to Land Rover’s.
What does p0171 and p0174 ford engine codes mean code#
The MAF signal that’s causing this code to set does not have an obvious problem, the signal looks ok at a glance. Take a look at the MAF signal graph display below. The best way to diagnosis these slight differences in MAF signal is with a scanner that has a good graph display. The signal voltage reads anywhere from 3.7-4.0 volts which is ok from my experience. Fuel pressure was within specifications (45-50 psi) and the MAF was reading correctly, I thought! I can hook up the scope and perform a snap throttle test. Then of course P0171 and P0174, lean both banks. The TCM (transmission control module) is setting incorrect gear ration codes which means the transmission is slipping (usually). The vehicle has no drivability concerns and was hard to diagnosis. Symptoms: NONE, Slight pre-detonation (pinging) when hot Vehicle: 2001 Land Rover Discover II Codes: P0171, P0174, TCM Incorrect Gear Ratio Mass Air Flow Sensor Testing,P0171-P0174 System Lean