P0172 on 2003 dodge Ram 1500 3.7L 6 cylinder
#11
#13
#15
I believe your truck came from factory with NGK 6987. Hopefully this change will help. You would not be first person with fuel trim problems that were caused by aftermarket plugs. I rec you put the plugs in and clear the codes.
Let us know if the codes come back. It is interesting that your plugs look lean but the code indicates rich. Your truck thinks it needs to reduce fuel. This would explain sluggishness during acceleration. Be sure to gap the plugs correctly.
Let us know if the codes come back. It is interesting that your plugs look lean but the code indicates rich. Your truck thinks it needs to reduce fuel. This would explain sluggishness during acceleration. Be sure to gap the plugs correctly.
Last edited by jrsick; 10-14-2021 at 07:43 AM.
#16
The screen shot you provide of the $11 code is great info for someone with reference materials for your vehicle. It's more detailed than standard OBDII scanners, but it is hard to come by the references to interpret that info.
Can you get a regular OBDII scanner?
What make/model scanner are you using now?
Can you get a regular OBDII scanner?
What make/model scanner are you using now?
#17
To answer the scanner question, I am using the iOBD2 by XTOOL, it is a small device you can purchase from Amazon for $29.99
So Friday, I put the new spark plugs in, I went with the NKG 6987 that I was able to verify in my Chilton’s manual as the OE. I reset the codes and started the truck up, for a brief moment, it seemed that the truck was actually idling smooth and for the first time, I saw the LTFT at 0.0 (at idle) for the first time, but my elation ended quickly as I drove Saturday morning, the CEL came back on and I saw the P0172 code back. I have reset the code again on Sunday and the truck idles around 700 rpm when I start, but, after I drive, the truck is racing at 1300 rpm in drive, the throttle position sensor is reading 22.7. I turn the truck off and back on and the idle is back to normal. Also, the STFT and LTFT are both at -33 at idle and the engine is running rough again. I have not had a chance to pull the O2 sensors yet, but I will do that this week.
So Friday, I put the new spark plugs in, I went with the NKG 6987 that I was able to verify in my Chilton’s manual as the OE. I reset the codes and started the truck up, for a brief moment, it seemed that the truck was actually idling smooth and for the first time, I saw the LTFT at 0.0 (at idle) for the first time, but my elation ended quickly as I drove Saturday morning, the CEL came back on and I saw the P0172 code back. I have reset the code again on Sunday and the truck idles around 700 rpm when I start, but, after I drive, the truck is racing at 1300 rpm in drive, the throttle position sensor is reading 22.7. I turn the truck off and back on and the idle is back to normal. Also, the STFT and LTFT are both at -33 at idle and the engine is running rough again. I have not had a chance to pull the O2 sensors yet, but I will do that this week.
#18
So we are all thinking same thing, it looks like you are getting a lean fuel trim. Fuel trim is based on O2 sensor output that is reading air before and after cat.
Try taking an IR sensor to your cat. Outlet side should be at least 100 degrees hotter than inlet.
Take readings of both O2 sensors. Rear sensor should be fairly steady while front sensor makes larger corrections. Do this test with warm engine, truck parked, and idle at 2000 rpm.
Try taking an IR sensor to your cat. Outlet side should be at least 100 degrees hotter than inlet.
Take readings of both O2 sensors. Rear sensor should be fairly steady while front sensor makes larger corrections. Do this test with warm engine, truck parked, and idle at 2000 rpm.
#19
so, after I got home from work, I ran the truck at 2000 rpms and measured the CAT, unfortunately, the unit I borrowed only goes to 482 degrees F, the inlet and the outlet were > 482 degrees F. I do have some thermocouples that can go higher, but I would have to hose clamp them one after the truck cools, I am pretty sure zip ties will not withstand that temperature. I did look at the O2 sensors, the voltage of both of them looked (to me the amateur) right on.
#20
Your O2 sensor data looks OK to me. The front sensor is cycling between rich and lean below .9 volts. The downstream is reading high, but that will not affect gas mileage or performance. Your plugs look like you may be lean.
If you are lean, it's likely in the fuel delivery vice fuel trim. Maybe fuel pump, fuel pressure regulator, or partially clogged fuel filter. I'll have to think on this some.
If you are lean, it's likely in the fuel delivery vice fuel trim. Maybe fuel pump, fuel pressure regulator, or partially clogged fuel filter. I'll have to think on this some.