Good afternoon guys. After all the work I recently had done, which I previously posted about, along with installing new o2 extension wires for the headers and new spark plugs, I'm getting a P0152 code. I have tried Seafoam, Redline and have had my fuel injectors professionally cleaned, too, but it keeps popping up. The car is running much better after the cleaning, but I noticed when I'm driving the car hard, there's hesitation at 6k RPMs. Do I need to replace the fuel injectors and coils? Not sure what else it could be.

You might have a leak somewhere...

Ilya wrote: ↑

Mon Nov 06, 2023 3:58 pm

You might have a leak somewhere...

Hmm, I cleaned my throttle body not too long ago, but I didn’t change the gasket. I wonder if that might be the problem. Is there an efficient way to check for leaks?

Your scanner can tell you whether you have a vacuum leak or not (although it can't tell you where). Monitor your Short Term Fuel Trims (STFT), if they go positive more than about 8~10% at idle but normalize toward zero when you raise the RPM's to 2K or more, there's a leak someplace.

VStar650CL wrote: ↑

Tue Nov 07, 2023 7:33 am

Your scanner can tell you whether you have a vacuum leak or not (although it can't tell you where). Monitor your Short Term Fuel Trims (STFT), if they go positive more than about 8~10% at idle but normalize toward zero when you raise the RPM's to 2K or more, there's a leak someplace.

That's great information!

Definitely great info. It took me in a new, and less expensive direction! LOL I changed the throttle body gaskets today, cleared the codes and did the throttle relearn process. Took the car for a nice long drive and rode it hard. The service engine light flashed once and went off and did not come back on. Drove it hard for another 30 minutes or so and no lights. Fingers crossed that this was the issue. If so, it will be on to some cosmetic improvements.

So today I replaced the PVC valves and checked the short term fuel trims. I didn't see anything that said STFT, but I did find SHRTFT1 and SHRTFT2. I'm assuming this is the same thing. The freeze frame result was -1.6%. I got my RPMs up to around 2k and it didn't change. Is that good or bad? Service light also came back on, too. I have ordered replacement ignition coils and will get those installed when they come. While I don't think the issue is the o2 sensor and/or wiring (new wire extensions installed with existing sensors two weeks ago), I'm beginning to wonder if it could be. I may replace both sensors when I do the ignition coils. Is it possible that I ruined the sensors by having bad A/F ratios for an extended period of time?

Different scanners use different abbreviations (Nissan doesn't actually call it STFT at all, they call it A/F-alpha). You were in the right place, and there's nothing wrong with a slight negative reading. The main thing is that there's no big change between idle and higher RPM's. If there's no change then there are no intake leaks.

You're chasing the wrong things anyway. P0152 is an open circuit code (flatlined high) for the passenger side A/F sensor (front O2). It's an electrical hard code, you either have a bad sensor or a wiring problem.

VStar650CL wrote: ↑

Sun Nov 19, 2023 6:03 am

Different scanners use different abbreviations (Nissan doesn't actually call it STFT at all, they call it A/F-alpha). You were in the right place, and there's nothing wrong with a slight negative reading. The main thing is that there's no big change between idle and higher RPM's. If there's no change then there are no intake leaks.

You're chasing the wrong things anyway. P0152 is an open circuit code (flatlined high) for the passenger side A/F sensor (front O2). It's an electrical hard code, you either have a bad sensor or a wiring problem.

You were right. Apparently the sensor was shorted out previously when the car was at the dealer (jackass mechanic let the wire harness sit on the header and the wires melted). I bought new ones and had them installed and now I'm all set. One interesting thing is I had to do an idle re-learn after the new sensors were installed. I'm not sure if the shop disconnected the throttle bodies or not, but halfway home from the shop I was getting P0300 codes. I did the idle re-learn and all was good.

On a side note, it's really, really hard to find a good mechanic in the Chicago area these days . The mess I had to go through with this process was insane. I'm thankful for everyone in this forum for their help and expertise. It helped me make sense of all the different information I was getting.

Glad to help, happy motoring.