p0121 after new fuel pump and tank coincidence or not?
03-04-2015, 06:36 PM
#1
Racer
Thread Starter
p0121 after new fuel pump and tank coincidence or not?
I already made a post in the tech section, but after doing so I figured I should post in FI being you guys will have more experience with boost a pumps and such.
Hey guys so Ive got an issue going on that I'm trying to figure out. So I had the dreaded fuel leak and ended up getting a new fuel pump and tank installed by the dealer. I just got the car back yesterday and went to take it for a drive WOT to make sure it behaves correctly. Well, it threw a p0121 which is the code for the TPS. I actually had this code thrown approx. 6 months ago intermittently and after cleaning the throttle body and unplugging then replugging the MAF connector on the air bridge the problem seemed to go away. Well now that it's back it makes me wonder whether it is just a coincidence that I just had the pump and tank replaced or if it could be related to the work performed. The car is supercharged with an A&A kit and is equipped with a boost a pump. Well while they were in there they noticed that the wiring for the fuel pump where the boost a pump is tied in looked chared we assume to be from a bad ground. They were going to get a new harness for back there but they are on backorder so he went ahead and repaired my current harness with new wire to fix the issue.
So my question is, is the p0121 code unrelated to what they did and is just a coincidence that it came back after the repair or is it possible that they poorly repaired the fuel pump wiring and is causing the code to display somehow because the boost a pump isn't operating correctly? I am no expert mechanic by any means but I am wondering if the boost a pump isn't working now so under boost conditions it is expecting X amount of air/fuel and isn't getting the proper amount so the car thinks that the TPS is the issue.
I do not have gauges for the car yet, it was going to be my next mod but haven't had the chance to do it yet so I have no way of looking at the air fuel, fuel pressure, etc.
Hey guys so Ive got an issue going on that I'm trying to figure out. So I had the dreaded fuel leak and ended up getting a new fuel pump and tank installed by the dealer. I just got the car back yesterday and went to take it for a drive WOT to make sure it behaves correctly. Well, it threw a p0121 which is the code for the TPS. I actually had this code thrown approx. 6 months ago intermittently and after cleaning the throttle body and unplugging then replugging the MAF connector on the air bridge the problem seemed to go away. Well now that it's back it makes me wonder whether it is just a coincidence that I just had the pump and tank replaced or if it could be related to the work performed. The car is supercharged with an A&A kit and is equipped with a boost a pump. Well while they were in there they noticed that the wiring for the fuel pump where the boost a pump is tied in looked chared we assume to be from a bad ground. They were going to get a new harness for back there but they are on backorder so he went ahead and repaired my current harness with new wire to fix the issue.
So my question is, is the p0121 code unrelated to what they did and is just a coincidence that it came back after the repair or is it possible that they poorly repaired the fuel pump wiring and is causing the code to display somehow because the boost a pump isn't operating correctly? I am no expert mechanic by any means but I am wondering if the boost a pump isn't working now so under boost conditions it is expecting X amount of air/fuel and isn't getting the proper amount so the car thinks that the TPS is the issue.
I do not have gauges for the car yet, it was going to be my next mod but haven't had the chance to do it yet so I have no way of looking at the air fuel, fuel pressure, etc.
03-04-2015, 09:15 PM
#2
Melting Slicks
Member Since: Mar 2007
Location: Santa Barbara CA
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I don't think I have any experience with that exact code, but I don't really see any connection to the fuel tank, pump, or BAP. When you go WOT, the PCM enters open-loop mode -- meaning it has no idea as to what's actually coming out the exhaust. That fault code has nothing to do with mixture control.
Just from a quick search, this seems like a MAP/throttle plausibility code -- meaning the pressure the MAP sensor is reading doesn't jive with the throttle angle. Not too shocking on an engine that's had a blower retrofitted. While I can't remember if it was this exact code, I had some type of MAP/TPS correlation code pop up on my old A&A car right after I put the blower on. Since it's happened to you before, I'm guessing it isn't a new issue. Maybe an intermittent one.
Just from a quick search, this seems like a MAP/throttle plausibility code -- meaning the pressure the MAP sensor is reading doesn't jive with the throttle angle. Not too shocking on an engine that's had a blower retrofitted. While I can't remember if it was this exact code, I had some type of MAP/TPS correlation code pop up on my old A&A car right after I put the blower on. Since it's happened to you before, I'm guessing it isn't a new issue. Maybe an intermittent one.
03-04-2015, 09:41 PM
#3
Race Director
Member Since: May 2004
Location: Raleigh, NC
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St. Jude Donor '15
I had this one pop up the other day when I started tuning higher RPM's..
from what I read at the time it sounded like it was an error between expected vs. actual throttle blade location, but I'm not 100% sure on that. I wonder if it's more related to a difference in actual airflow was measured?
Found this on it:
from what I read at the time it sounded like it was an error between expected vs. actual throttle blade location, but I'm not 100% sure on that. I wonder if it's more related to a difference in actual airflow was measured?
Found this on it:
P0121 - GM
Type Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description
TP Sensor Performance Conditions
Cause
No MAP or TP sensor codes set, engine running, ECT input over 158°F, MAP input under 50 kPa or over 70 kPa, MAP input steady, and PCM detected the Actual TP input was over the Calculated TP input with MAP input under 50 kPa, or was below the Calculated MAP input with the MAP input over 70 kPa for 10 seconds.
Type Powertrain - Fuel and Air Metering - ISO/SAE Controlled
Description
TP Sensor Performance Conditions
Cause
No MAP or TP sensor codes set, engine running, ECT input over 158°F, MAP input under 50 kPa or over 70 kPa, MAP input steady, and PCM detected the Actual TP input was over the Calculated TP input with MAP input under 50 kPa, or was below the Calculated MAP input with the MAP input over 70 kPa for 10 seconds.
Last edited by schpenxel; 03-04-2015 at 09:43 PM.
03-05-2015, 10:47 AM
#4
Racer
Thread Starter
Awesome, thank you for your input guys! When I looked this issue up when it happened months ago, the consensus is either TPS, TB, accelerator pedal assembly, or wiring. I am going to go ahead and get a new throttle body I guess, being there is no way I know of to determine which is causing the issue. Ill probably just go ahead and get a ported one, so at least ill get a small gain out of it. If that doesnt fix it Ill try to change out the pedal assembly, hopefully it wont be a wiring issue.