PO121 code after LQ4 swap
Thread Starter
Staging Lane
Joined: May 2009
Posts: 76
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From: Waco,Tx
PO121 code after LQ4 swap The car was dyno tuned last week and retweaked by the tuner yesterday.
After about 60 miles of driving my SES light comes on.
It gives me the PO121 code, TPS. Well I changed the tps last thursday cleared the code. The ses came back on saturday and I didnt really worry about it because I was taking it back to the tuner on monday.
Driving home today the ses comes back on with the same code.
I cant figure it out, any ideas?
After about 60 miles of driving my SES light comes on.
It gives me the PO121 code, TPS. Well I changed the tps last thursday cleared the code. The ses came back on saturday and I didnt really worry about it because I was taking it back to the tuner on monday.
Driving home today the ses comes back on with the same code.
I cant figure it out, any ideas?
Teching In
Joined: Feb 2022
Posts: 5
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I was replying to the original person being he just got it tuned.
On yours I would carefully check your grounds and harness really well to make sure something isnt back feeding your TPS signal.
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I've searched the whole internet for this problem dawg. Everyone's problem is either a bad tps or they just got their engine tuned.
On AllData, it says a bad map sensor can trigger this code but, the map is working as it should. I keep a scanner plugged in as I drive to monitor the graphs but, nothing that I can see is messing up.
TECH Fanatic
Joined: Oct 2014
Posts: 1,220
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From: Virginia
I checked everything I could wire wise, including shaking the f*** out of the harness at different points.
I've searched the whole internet for this problem dawg. Everyone's problem is either a bad tps or they just got their engine tuned.
On AllData, it says a bad map sensor can trigger this code but, the map is working as it should. I keep a scanner plugged in as I drive to monitor the graphs but, nothing that I can see is messing up.
I've searched the whole internet for this problem dawg. Everyone's problem is either a bad tps or they just got their engine tuned.
On AllData, it says a bad map sensor can trigger this code but, the map is working as it should. I keep a scanner plugged in as I drive to monitor the graphs but, nothing that I can see is messing up.
1. Your TPS is in fact working and registering the appropriate voltages.
2. Your car is (assuming) running perfectly fine.
3. You have this code for no apparent reason and your TPS voltage is below 0.7 volts at idle.
With the above facts, my next step is... Go into the tune, then:
1. Go to > Engine Diag > Airflow
2. Set the P121 test to 0 and 100 appropriately
End task.
Option 2:
Go to the actual code under engine diag and set to "No error reported" since your cable anyway and it doesn't f'n matter and move on with life.
Either is appropriate really. Both should satisfy removing the annoying light. To me, you kind of have to resolve this to save the light for real problems like a MAF fail, O2 fails, knock, and other real issues that will actually cause damage.
Case in point, this code is nothing to a cable car, because it's a damn cable determining the actual throttle position. If it is providing accurate voltage and percents from 0 to 100, and some wonky number in some calculation somewhere is throwing this code, you are fine. Just get rid of the stupid code because it is not actually harmful to your motor. Different story completely if you are on a DBW TB. But cable? Nope. Just an issue for an automatic transmission if the numbers are janky. It's about the only problem that code can cause in reality for a cable car. That and PE entry. Also an issue. That said, if the numbers are good, like stated before, the code is bogus.
Last edited by ChopperDoc; Feb 12, 2022 at 02:05 AM.
TECH Fanatic
Joined: Oct 2014
Posts: 1,220
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From: Virginia
*Note: If you go with option 2 above, you will NOT get an CEL/SES light if the TPS sensor ***** the bed. You will however get weird shifting, and bad AFRs in PE (if it even enters PE). If this occurs, you should already know to investigate the TPS sensor knowing that it is disabled and will affect both of those things. Having said this, option 1 is the best course of action, provided it works for you. If not, you just need to accept that you won't have TPS fail detection and you have to know the symptoms of said failure. #justmechainic/tunerthings
Last edited by ChopperDoc; Feb 12, 2022 at 02:07 AM.
