The customers concern is the check engine light on with a Diagnostic trouble code stored in the computer of P0171 indicating the fuel trims are too high and the engine is running lean. One of the most common trouble codes with the Toyota 4Runner is the P0171 code. I go back and am able to pass smog. This will not affect the way the engine accelerates. So it it has a vacuum leak, it will show up at idle or lower engine rpms and usually cause a surging or high idle condition if the vacuum leak is large enough. I disconnected negative side of battery to try and clear code.
Tech notes If the P0171 is combined with the P0174 code, it's very likely that the problem is caused by an intake leak. Another known issue in Ford vehicles is a vacuum leak from a ripped-through rubber elbow on one of the vacuum lines at the back of the intake manifold. If the fuel trim suddenly shoots the other direction rich then you have found the area at fault. When faced with this issue, replacing the piston rings should fix it. Drive for a month then the light comes back on.
Usually what happens is the sensing element on the mass air flow sensor gets dirty and it cannot measure the amount of air coming into the engine properly. I've never changed just the pump before, usually I get the whole assembly. Soon as I did all this the P0171 was gone. Based on my experience, the mass air flow sensing element gets dirty because of a dirty air filter that has not been serviced or replaced regularly. If that doesn't work anybody have any suggestions. The last time my light was on it was because of the gas cap so I just pulled the fuse and reset the light.
Check engine light on: P0171 System Too Lean, Long term fuel trim at 35. Could be the fuel pump? In the process I noticed that the negative lead from the battery to chasis ground was broke. Toyota Technical Service bulletin 0074-08 addresses these codes. The calculated load reading should increase to 85% or higher on a wide open throttle acceleration. I took it to auto store to put on computer. I have cleaned the maf, replaced the maf with new, replaced fuel filter , replaced tps , fixed exhaust leaks, checked for vacuum leaks. Typically the code will be triggered by a lean condition in the engine.
Lean code P0171, but the engine is running very rich. Good luck figuring out what is wrong with your 4Runner. Toyotas seem to get hit hard with this code and you can waste a lot of time chasing it. If so, the sensor is faulty and will need to be replaced. I've been having the same problem as all of you. The coils and fuel injectors might have been a bit hasty without a misfire code. Take a look around and see if you can find the vacuum leak.
I will go over some of the more common ones I have seen on a Toyota Corolla and even the Toyota Matix as they use the same 4 cylinder engine. The master mechanic said that one of the other mechanics had my same car 97 Camry and he too had the exact same problem - hesitation in power, followed by check engine light, followed by lean condition codes. If anybody has any ideas please let me know. If it is a California vehicle its a bit of a different approach. I would think that better mileage would mean better emission. Took truck back to get p0171 code cleared, now along with p0171, the computer also got p0113 and p0102 codes.
I have seen this vehicle with a number of trouble codes including the P0171 lean code stored in the computer. Much appreciated was that he got the parts to be covered by Toyota and I just had to pay for the labor only. It was driven on the highway for about 4 hours after getting the code and there is no noticeable change in mileage, the way it runs, no funny smells, etc. They are barely noticeable and the car seems to drive just fine. If the oxygen sensor shows low voltage and the fuel trim readings climb, check the performance of the oxygen sensor.
The brake booster is vacuum assisted and works off of engine vacuum. Two weeks later the light comes on again. Anyway, I've had to learn a ton about this stuff because I'm military stationed overseas, in the middle east, with not lots of local parts or expertise. Or Is there any way to reset the computer? This is the same engine, sensor and set up as the 07 Toyota Camry with a 2. I drove with it on for a few months and several thousand miles with pretty much no problems. First is a brief overview of this code. The funny thing is that with p0171 code, my Mileage went up from 23-24 Miles per Gallon to 25-26 Miles per Gallon.
Twist them and manipulate them a little to make sure they aren't cracked or split. We have done some research and posted common problems for some cars, please read further. If there is an aftermarket type of air filter, remove it and see if the fuel trims remain normal. Basic checks under the hood include: is the air filter box properly closed? Fuel injectors The fuel injectors are also a common concern for these codes on this 3. I've been able to clear the Check engine light but it comes back. Does anyone have a list of things to do in order of likelihood? If the numbers are low at idle but climb on a part throttle cruise, the airflow meter could be reading low or it may also have low fuel pressure.
The updated part number for the right hand side exhaust manifold is. My check engine light came on the other day while I was driving on the highway. The mass air flow sensor grams per second should be 3. All 4 wires should read voltage; 12 volts for the heater voltage input, 3. I am a little confused now. Without Stability Control the O. If the fuel trim readings are high at idle and at cruise, suspect fuel injectors.