P2121 Code and Erratic Acceleration
06-10-2015, 12:55 PM
#1
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P2121 Code and Erratic Acceleration
Hey everyone, I was wondering if anyone could provide some insight on this code I got today. Digging didn't do me too much good. The car is accelerating for the most part normal but I can tell somethings off. Sometimes it will feel like a misfire and sometimes it accelerates more than I expect it would.
06-11-2015, 04:30 AM
#2
P2121 - Throttle/Pedal Position Sensor/Switch "D" Circuit Range/Performance
OBD-II code P2121 indicates a problem with the accelerator pedal position, or APP, sensor.
The accelerator pedal position sensor is located on the accelerator pedal bracket. This pedal position sensor has two sensor elements and two signal outputs which are VPA & VPA2. VPA is there to detect problems in the VPA. When there are differences in the voltage outputs of the VPA and VPA2 that are different from the standard, the ECM will determine that the accelerator pedal position sensor is not functioning properly.
There is only one common cause of the P2121 trouble code and that’s the accelerator position sensor itself. In many applications, this sensor is in need of replacement. Other symptoms of a bad accelerator pedal position sensor include erratic throttle response and a pedal that will go “dead” while there is power to your vehicle. In very rare circumstances, any trouble codes that won’t go away, even after faulty parts are replaced, could indicate problems with the engine control module, or ECM. Problems with the ECM include poor performance and erratic shifting for automatic transmissions.
OBD-II code P2121 indicates a problem with the accelerator pedal position, or APP, sensor.
The accelerator pedal position sensor is located on the accelerator pedal bracket. This pedal position sensor has two sensor elements and two signal outputs which are VPA & VPA2. VPA is there to detect problems in the VPA. When there are differences in the voltage outputs of the VPA and VPA2 that are different from the standard, the ECM will determine that the accelerator pedal position sensor is not functioning properly.
There is only one common cause of the P2121 trouble code and that’s the accelerator position sensor itself. In many applications, this sensor is in need of replacement. Other symptoms of a bad accelerator pedal position sensor include erratic throttle response and a pedal that will go “dead” while there is power to your vehicle. In very rare circumstances, any trouble codes that won’t go away, even after faulty parts are replaced, could indicate problems with the engine control module, or ECM. Problems with the ECM include poor performance and erratic shifting for automatic transmissions.
06-12-2015, 03:40 PM
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This looks like the whole pedal assy:
78010-21020
but it's crazy expensive new ($300+)! Just search for a used tc1 pedal assy on ebay. I saw one with the sensor for $25 +$5 shipping. You don't want to spend too much on these becase they don't typically go bad, and you don't want to start throwing expensive parts at this since you haven't 100% confirmed the issue.
78010-21020
but it's crazy expensive new ($300+)! Just search for a used tc1 pedal assy on ebay. I saw one with the sensor for $25 +$5 shipping. You don't want to spend too much on these becase they don't typically go bad, and you don't want to start throwing expensive parts at this since you haven't 100% confirmed the issue.
06-17-2015, 11:52 PM
#6
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So I broke apart the old sensor today and everything looked fine. I cleaned the contacts and popped it back in and same issue. Check engine light hasn't come on yet but I'm sure it will eventually.
http://imgur.com/oOnZP8X
Next step? I'm very confident the new sensor will not fix this issue.
http://imgur.com/oOnZP8X
Next step? I'm very confident the new sensor will not fix this issue.
06-18-2015, 11:12 PM
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Thanks but that doesn't seem to help me much.
I got the new sensor in today and still have the same issue. The car is almost sputtering after it is warmed up completely and anytime I shift into neutral after having sped up, the car dies
I think next step would be to replace ECU? I was reading that Camrys with this code were able to replace the throttle body and resolve the issue. Could someone explain why that might be?
I got the new sensor in today and still have the same issue. The car is almost sputtering after it is warmed up completely and anytime I shift into neutral after having sped up, the car dies
I think next step would be to replace ECU? I was reading that Camrys with this code were able to replace the throttle body and resolve the issue. Could someone explain why that might be?
06-19-2015, 12:10 AM
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Do you have a scan tool? Can you monitor your throttle position with the car off but ignition on, and then at idle? Also blip the throttle a few times with only the ignition on and see if the scan tool registers the change. I'm trying to see if you can possibly trace a throttle position issue to the pedal or throttle body.
06-19-2015, 01:30 AM
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I'm using a bluetooth obd2 reader and the app Torque so I can't get a ton of information.
Car off, ignition on, throttle position reads 18.8%
With CEL and the car in "safe mode" or whatever where I have to push the gas pedal down twice as hard to get the same amount of power:
at idle, throttle position reads 17.7%
Gas pedal down more than half and rpms at ~7k, throttle position reads ~60%
Next I cleared the CEL and the car accelerates with normal pressure to the gas;
at idle, throttle position reads the same 17% and with gas pedal at ~7k rpms, throttle position reads the same ~60%.
I'm never at 0 or 100%.
Another factor that has to be related, is that my brake light comes on during acceleration and off when not. I previously though this was due to tensioning my e-break pads too tight because it only came on when the car was cold (before turbo) and if I lightly yanked on the e-brake while driving the light would disappear. If it was warm out this would never happen. Now even though it is warm out, it always comes on and turns off randomly. For the first time now, I was able to notice that the light comes on during hard acceleration and off otherwise.
Another side note that might also be related (my other thread explaining why my idle is so low right after a cold start): Here are my tune values:
This is my descendant turbo tune base map, in case anyone else comes across this down the road and wants to check it out:
https://drive.google.com/file/d/0B1y...ew?usp=sharing
And here is my dyno sheet:
https://drive.google.com/file/d/0B1y...ew?usp=sharing
When I go to read fuel trim values (1x1,1x2,1x3,1x4;2x1,2x2,2x3,2x4) they all read a dash like nothing shows up. When I read the general fuel trim radio it says 98%?
Car off, ignition on, throttle position reads 18.8%
With CEL and the car in "safe mode" or whatever where I have to push the gas pedal down twice as hard to get the same amount of power:
at idle, throttle position reads 17.7%
Gas pedal down more than half and rpms at ~7k, throttle position reads ~60%
Next I cleared the CEL and the car accelerates with normal pressure to the gas;
at idle, throttle position reads the same 17% and with gas pedal at ~7k rpms, throttle position reads the same ~60%.
I'm never at 0 or 100%.
Another factor that has to be related, is that my brake light comes on during acceleration and off when not. I previously though this was due to tensioning my e-break pads too tight because it only came on when the car was cold (before turbo) and if I lightly yanked on the e-brake while driving the light would disappear. If it was warm out this would never happen. Now even though it is warm out, it always comes on and turns off randomly. For the first time now, I was able to notice that the light comes on during hard acceleration and off otherwise.
Another side note that might also be related (my other thread explaining why my idle is so low right after a cold start): Here are my tune values:
This is my descendant turbo tune base map, in case anyone else comes across this down the road and wants to check it out:
https://drive.google.com/file/d/0B1y...ew?usp=sharing
And here is my dyno sheet:
https://drive.google.com/file/d/0B1y...ew?usp=sharing
When I go to read fuel trim values (1x1,1x2,1x3,1x4;2x1,2x2,2x3,2x4) they all read a dash like nothing shows up. When I read the general fuel trim radio it says 98%?
Last edited by skruff; 06-19-2015 at 01:43 AM.
06-19-2015, 05:23 PM
#11
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Side note- will this throttle body work with my TC or does it need to be the 22030-0H021 type?
06 10 Scion TC Camry Corolla RAV4 XB Throttle Body Valve Assm 232 | eBay
For $40 I figure I'll just swap out my existing one before taking the car in to the shop.
06 10 Scion TC Camry Corolla RAV4 XB Throttle Body Valve Assm 232 | eBay
For $40 I figure I'll just swap out my existing one before taking the car in to the shop.
06-27-2015, 06:44 PM
#14
The brake light coming on during acceleration sounds like an issue I had and it was due to my brake pads being worn and needing replacing.
So either your pads need replacing or you're low on brake fluid. Or possibly even both.
So either your pads need replacing or you're low on brake fluid. Or possibly even both.
06-28-2015, 10:48 PM
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I have checked pads and rotors and done my research on that end- fluid is also fine. I got another code finally for 2123 which leads me to believe this is related to my ECM, wire harness, or wires going from the sensor to the ECM. Will report back after I do some testing with my multimeter.
06-29-2015, 12:57 AM
#16
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So I checked my sensor values at the ECU and they looked fine. The idle depressed voltage was low for VPA so I unbolted and repositioned the sensor so that it would be within reccomended specs:
No fault codes were logged after this but it usually doesn't show up until after ~25 miles or so. This is a screenshot of me pressing the gas pedal down hard and then instantly releasing it. Should this be more smooth?
Although there weren't any fault codes and I didn't have a "dead" pedal yet, this is me in 3rd gear with the cruise control on:
It feels as though the car is lurking forward. Shouldn't it be much more smooth? Its almost as if I were in neutral and then dropping the clutch; speeding up some; putting it in neutral; finally, dropping the clutch again.
Again I am lost as to what to do next, because the voltages were fine for the sensor and throttle position (seemed) okay and responsive.
No fault codes were logged after this but it usually doesn't show up until after ~25 miles or so. This is a screenshot of me pressing the gas pedal down hard and then instantly releasing it. Should this be more smooth?
Although there weren't any fault codes and I didn't have a "dead" pedal yet, this is me in 3rd gear with the cruise control on:
It feels as though the car is lurking forward. Shouldn't it be much more smooth? Its almost as if I were in neutral and then dropping the clutch; speeding up some; putting it in neutral; finally, dropping the clutch again.
Again I am lost as to what to do next, because the voltages were fine for the sensor and throttle position (seemed) okay and responsive.
06-30-2015, 01:33 PM
#18
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I'm using a bluetooth obd2 reader and the app Torque so I can't get a ton of information.
Car off, ignition on, throttle position reads 18.8%
With CEL and the car in "safe mode" or whatever where I have to push the gas pedal down twice as hard to get the same amount of power:
at idle, throttle position reads 17.7%
Gas pedal down more than half and rpms at ~7k, throttle position reads ~60%
Next I cleared the CEL and the car accelerates with normal pressure to the gas;
at idle, throttle position reads the same 17% and with gas pedal at ~7k rpms, throttle position reads the same ~60%.
I'm never at 0 or 100%.
Another factor that has to be related, is that my brake light comes on during acceleration and off when not. I previously though this was due to tensioning my e-break pads too tight because it only came on when the car was cold (before turbo) and if I lightly yanked on the e-brake while driving the light would disappear. If it was warm out this would never happen. Now even though it is warm out, it always comes on and turns off randomly. For the first time now, I was able to notice that the light comes on during hard acceleration and off otherwise.
Another side note that might also be related (my other thread explaining why my idle is so low right after a cold start): Here are my tune values:
When I go to read fuel trim values (1x1,1x2,1x3,1x4;2x1,2x2,2x3,2x4) they all read a dash like nothing shows up. When I read the general fuel trim radio it says 98%?
Car off, ignition on, throttle position reads 18.8%
With CEL and the car in "safe mode" or whatever where I have to push the gas pedal down twice as hard to get the same amount of power:
at idle, throttle position reads 17.7%
Gas pedal down more than half and rpms at ~7k, throttle position reads ~60%
Next I cleared the CEL and the car accelerates with normal pressure to the gas;
at idle, throttle position reads the same 17% and with gas pedal at ~7k rpms, throttle position reads the same ~60%.
I'm never at 0 or 100%.
Another factor that has to be related, is that my brake light comes on during acceleration and off when not. I previously though this was due to tensioning my e-break pads too tight because it only came on when the car was cold (before turbo) and if I lightly yanked on the e-brake while driving the light would disappear. If it was warm out this would never happen. Now even though it is warm out, it always comes on and turns off randomly. For the first time now, I was able to notice that the light comes on during hard acceleration and off otherwise.
Another side note that might also be related (my other thread explaining why my idle is so low right after a cold start): Here are my tune values:
When I go to read fuel trim values (1x1,1x2,1x3,1x4;2x1,2x2,2x3,2x4) they all read a dash like nothing shows up. When I read the general fuel trim radio it says 98%?
My next question is about your fuel map. Do you know what size injectors you are running? If you are running larger then oem, I would have expected your fuel map to be a negative number outside of boost (~14.9 psia on the map above). This is because outside of boost, you would want to trim the larger injectors to flow like stock. That is, if you are running 550cc injectors, I would expect a trim of about -42% (or thereabouts) to flow similar to the stock of about 320cc. Your map seems to be in the positive range while still in vacuum, meaning it's dumping a lot of fuel. I imagine this may be causing your cold start issue.
I am also using the torque pro program as well. Add gaues to monitor "Long term fuel trim bank 1" and "short term fuel trim bank 1" Check these during a cold start and monitor them until the car warms up and is in closed loop. I'm really thinking that the ecu is going to pull a ton of fuel at idle to compensate for the excessive fuel in your map. I don't know is this is related to the throttle response issue you are having, but perhaps we can start here and see where it goes.
06-30-2015, 06:21 PM
#19
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Ok, I believe what you are saying about throttle position is normal. I vaguely remember mine doing the same thing. It never reached the upper or lower percent limit.
My next question is about your fuel map. Do you know what size injectors you are running? If you are running larger then oem, I would have expected your fuel map to be a negative number outside of boost (~14.9 psia on the map above). This is because outside of boost, you would want to trim the larger injectors to flow like stock. That is, if you are running 550cc injectors, I would expect a trim of about -42% (or thereabouts) to flow similar to the stock of about 320cc. Your map seems to be in the positive range while still in vacuum, meaning it's dumping a lot of fuel. I imagine this may be causing your cold start issue.
I am also using the torque pro program as well. Add gaues to monitor "Long term fuel trim bank 1" and "short term fuel trim bank 1" Check these during a cold start and monitor them until the car warms up and is in closed loop. I'm really thinking that the ecu is going to pull a ton of fuel at idle to compensate for the excessive fuel in your map. I don't know is this is related to the throttle response issue you are having, but perhaps we can start here and see where it goes.
My next question is about your fuel map. Do you know what size injectors you are running? If you are running larger then oem, I would have expected your fuel map to be a negative number outside of boost (~14.9 psia on the map above). This is because outside of boost, you would want to trim the larger injectors to flow like stock. That is, if you are running 550cc injectors, I would expect a trim of about -42% (or thereabouts) to flow similar to the stock of about 320cc. Your map seems to be in the positive range while still in vacuum, meaning it's dumping a lot of fuel. I imagine this may be causing your cold start issue.
I am also using the torque pro program as well. Add gaues to monitor "Long term fuel trim bank 1" and "short term fuel trim bank 1" Check these during a cold start and monitor them until the car warms up and is in closed loop. I'm really thinking that the ecu is going to pull a ton of fuel at idle to compensate for the excessive fuel in your map. I don't know is this is related to the throttle response issue you are having, but perhaps we can start here and see where it goes.
RC High Flow Fuel Injectors: 440cc / 550cc / 750cc
The fuel banks should be at about what numbers at startup and after several minutes? Anything above 10 would be bad?
Is this something that I can fix with the AEM software or will I have to take it up with my tuner?
06-30-2015, 08:57 PM
#20
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Well, I imagine the LTFT and STFT may not even register when cold, since the ecu is not adjusting your fuel ratios. When warm, that's when you should see the fuel trims in realtime. As a goal, the total trim should be less than +/-10% (adding both the STFT and LTFT). If you are seeing more than that, then the ECU is trying really hard to correct for excessive fuel.
Your tuner should have adjusted this for you by modifying your fuel map until the fuel trims (long term and short term) are as close to zero as possible in the closed loop range. I wouldn't be surprised if this wasn't done, as this is a quirk of using a piggyback ECU and is basically an extra step.
The other thing that will also need to be looked at is the "injector response time" under "setup" in the fic software. I don't know what this needs to be for you injectors, so you may need to do some trial and error. If you do a search on this forum, you may get lucky and find a a recommended setting for these injectors. Generally, larger injectors need a longer response time (the time needed for the injectors to fully open).
Your tuner should have adjusted this for you by modifying your fuel map until the fuel trims (long term and short term) are as close to zero as possible in the closed loop range. I wouldn't be surprised if this wasn't done, as this is a quirk of using a piggyback ECU and is basically an extra step.
The other thing that will also need to be looked at is the "injector response time" under "setup" in the fic software. I don't know what this needs to be for you injectors, so you may need to do some trial and error. If you do a search on this forum, you may get lucky and find a a recommended setting for these injectors. Generally, larger injectors need a longer response time (the time needed for the injectors to fully open).
