Code Po174?

Hi,

Anything that can cause an engine vacuum leak can cause this code. Have you checked all vacuum hoses, intake manifold, PCV valve, and so on for leaks? If you haven't, start with that. Also, if your scanner has a live data setting, let me know what the short-term fuel trims are.

What I suggest as far as the canister is, see if you can determine where the air is coming out when you blow through it.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know,

Joe

Joe, hello, thank you for answering. I checked all the above, that you said, that is why I was asking about the 2 Terminal purge Valve solenoid. Here is a picture of what I was asking. Also, I just found this burnt plug that goes to the purge valve solenoid. Here is the short trims data freeze.

Joe, codes came back this time a po174 and po171.

Joe, here’s the picture of what I was talking about blowing in purge solenoid.

Hi,

Replace it. That shouldn't allow air to escape. I do have another question. I am looking at the fuel trims you provided. Am I reading that correctly (32.8% and 99.1%)? If I am correct, there is a serious vacuum issue or very low fuel pressure. So, I would replace the purge solenoid and inspect the connector that is burnt. I don't like how that looks. Make sure the pin in the connector isn't damaged. Clean it as best as you can.

Let me know.

Joe

Will do Joe.

Joe, I was looking around for a vacuum leak an I found this little hose crack good, can this be a vacuum leak for lean code?

This part of the EGR valve solenoid.

Hi,

Absolutely! Have you been able to make the repair? Has it changed the way it runs?

Let me know.

Joe

Joe, i was going to put evap on but i had it checked and it was good. The one i was ask about , to blow in air was one bought online, and it was bad. So, i put a new IAC valve, because when i can to a stop the truck would acts up And when I would put on the air condition The check engine light would come on all the time Also The truck would pool Like if I was giving it gas. it was running good for about a week , fell the difference right away, But this morning I didn't warm up the truck And as I was driving The check engine light came on. The codes came back PO171 P0174 But I was looking at the scanner and I noticed short-term And long-term trans were looking good But My MAF sensor Was reading 0.01 at idle and also when i was driving. I took it off a few days ago and cleaned it i wondering if i didn't put something back right. should the MAF sensor be at 0.01 or 0.04 is when i give it gas? Another thing, what would cause the check engine light to come on every time I turn on the heater or air conditioner? Because I know I don't have a vacuum leak I've checked everything from the gas tank all the way around the engines I had put a new PCV valve long time ago about it a year ago and changed it EGR a few things It just seems like This code keeps coming up but the truck is running way better since I changed the IAC . I just want to pass this smoke check. And thank you for your help. You put me in the right direction or letting me know about the short trims and long trims That was really helpful.

Hi,

Based on what the readings are for the MAF, it sounds faulty. When running, it should vary between 1v and 5v.

If you take a look below, I attached the voltages expected. You have a bad MAF based on what you are getting.

Let me know.

Joe

See pic below.

Joe, it was going well but a code po 443 po 171 po174. It was driving better than ever but this code can on. I put new evap, MAF , IAC, EGR, DPFE , 02 sensors check for vacuum, fuel pump, spark, plugs, battery. But the same old code always comes up po171, po174 with other codes? So, now I was reading about this code po443 on PCM. I have been reading about the purge solenoid. Remember Back I sent a picture of that burnt spot ? now I’m wondering could I had shorted the PCM because when I test the Evap plug I get power and ground but I don’t know now to check for short in wires . And how do I get a wire diagram for a PCM and the evap purge solenoid? Thanks Joe, I really believe that burnt spot has something to do with the vehicle giving me all these codes.

Hi,

As far as the wiring is concerned, I attached the entire wiring schematic for the powertrain circuits. I highlighted the PCM and purge valve for you.

The schematic was four pages long, but I had to cut each pic in half to make them readable. I did overlap them so you can follow from one to the next.

Starting with pic 9 below, I included the diagnostics for the codes 171 and 174. If I am reading the diagnostics correctly, there has to be a vacuum leak at some point.

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below.

Thanks so much.

Hi,

No problem whatsoever. If you have a chance, let me know how things turn out. I'm interested in knowing. Also, let me know if there is anything I can do to help.

Take care,

Joe

The truck runs a lot better, but it keeps getting a code p2195 and p171 , not at the same time, I was testing the PCM to the evap purge sensor and when I checked the Voltage on the connector positive and negative , I get 11.63 Volts and when I put the positive on the connector evap purge and the negative on the battery I get 10.39 Volts , I read something that says they should be the same voltages .? Now on 02 sensors I get this code, single biased/stuck lean bank sensor 1. I notice bank 1 sensor 1 and bank 2 sensor 1 , both kind of move up and down on scanner but bank 1 sensor 2 and bank 2 sensor 2 stay around 0.710, could the 02 sensors be bad ? See I put a four pack of O2 sensors. Supposedly they both to be universal but I noticed all four O2 sensors look the same the two in back 02 sensors are fat and kind of long and I heard the upper stream O2 sensors are supposed to be a little short and fat.

I don’t know what happened, but I wanted to also to say that tomorrow I’m going to do a smoke test but it seems like every time I leave the car sitting for a day or two that’s when I get the check engine lights. I’m kind of thinking the PCM computer is not working right that’s why I’m getting these codes.

Hi,

The STFT bank 2 indicates the computer is trying to dump fuel to make up for a lean mixture. As far as the sensors are concerned, the voltages shown are good. The only thing I can say is if they are not changing from that voltage.

Do all of the original codes return?

Joe

On warm up it keeps getting p2195 and pp2197 and I feel rough idling. When I don’t let it warm up, I get the p171 and p174 on same banks 1,2 and 2,1. I patched all the exhaust pipes and muffler for cracks and holes. How about the purge solenoid? Voltage. The 11.63 and 10.39 V ?

Joe, I have a question about the O2 sensors for my truck. What is the ohm resistance for the O2 sensors? I was testing them today, on my upstream I’m getting 3.3 Ohm one side and the other side I am getting 15.2 to 10.4 ohms. These are new ones I just put on and that why I am getting these codes p2195, p2197, on the old 02 sensors i only got one code. Someone told me that the ohms resistance should be 10 to 20 ohms?

Hi,

Normally, I'm looking for between 2 and 14 Ohms, so you are not far off. Are getting power to them? If you have a live data scan tool, watch how the sensors are reacting with the engine running. They should be producing between .01V and 1.0V.

Let me know if that is something you can do.

Take care,
'
Joe

Yes, Joe, it was my IAC, and the problem also was my fuel filter not sealing right I spray soap water around fuel filter seals on both sides of fuel filter and was getting a lot of bubbles on one side, a lot. I believe the reason why I was getting the other codes was because of a vacuum leak that was causing the other parts not to work correctly, right? I Been after this for over a year and some, but just recently it just started getting really bad where I couldn’t pass a smog. The clips where bent and not sealing it right Thank you for your help, you said it was a vacuum leak and you were right, out of all places the fuel filter I never thought about that one I checked the lines on the gas tank everything but except that one spot. My son just happened to mention it ,Thanks again. I really appreciate it. Hopefully after a month it should be good, but she’s running like a gorilla now. Also thank for helping me learn more on reading these scanner codes, and what they mean that really helped a lot.

Hi,

You are very welcome. I'm glad to hear you found the issue and that it's running good for you again.

Feel free to come back anytime in the future. You are always welcome here.

I hope you and your family have a nice Thanksgiving.

Take good care of yourself,

Joe