Hi all. two months ago my car had problems starting and stalled on the road during a snowstorm. They finally found the problem which they said was a relay(?). I don't know what that is but it seemed to at least get the car running. However the engine light remained on, and being fearful of more expenses, I just asked them if it was safe to drive, they said yes and what the code was. It was code 121, throttle position sensor. I noticed the hesitation, low gas mileage, rpm problems at idle, and went home and checked on the computer, and sure enough the symptoms matched the code. After driving my car for afew daysto test it, I looked in to getting the part, and a friend got one used. This fixed the problem about 75%, so I was tempted to just go with it, since the only remaining symptom was occasional hesitation. Specifically, I can't slowly accelerate, which I had trouble doing anyway because the gas pedal always has seemed stiff to me. you try to put your foot down and either the pedal doesn't move at all, or goes down too much(for my liking,I would prefer the pedal to go down more smoothly, but I don't know if a stiff pedal could have caused this problem, maybe a censor works better with a softer pedal).Anyway if my car does hesitate(only after a stop), I just lessen the pressure on the gas, and the car speeds up. once I am up to 10 mph, everything is normal.If I don't put enough pressure from a stop, there is no room to back off if it hesitates, and if someone is behind me, Ihave no choice but to gas it, and then it goes. Finally I called the hyundai dealership and asked them if anything else could be causing this problem, and they said an air flow meter. I asked if that would cause the same code, they said no. So I took the chance that the used tps was no good and bought another one-new. I then went to change my oil, where they do free code readingsand again, code 121, which was fine, I new the code would still be there and was happy their wereno other codes. I would say the car is better than with the used tps, but the damn light came back on and their is still some hesitation.Does it take awile for the new tps to work? Is their anything special about installing it? It seems like just 2 screws and a clip, which is all I did. How specific does the positioning of the sensor have to be?Does a crappy tps make my throttle body clog up and this needs to be clean? Is their anything else that could cause this(change spark plugs)? The one think that hit me just today is maybe the tps, being electrical is being set off by the relay replacment which is also electrical, or maybe they didn't replace that relay thing properly, or it was a defective part(I am just guessing, maybe this is stupid). The other thing electrical I noticed is my left headlight doesn't work sometimes when it is cold, so I honk the horn, and it immediately goes on. Seems like an elctrical problem.

 

Did you simply remove the original TPS and replace with the used one? There is a procedure you must follow when installing a TPS to make sure the voltage being passed from the sensor to the Engine Control Module is within correct limits at both closed and open throttle settings. This process also tells you if the TPS is operating as designed. If you just installed the part without further adjustment, I can see why you continue to get TPS error codes. I wouldn't mess with the MASS aiflow sensor until you know the TPS is working correctly and within tolerances. I'm guessing you won't have to once the TPS situation is corrected.

This is an odd one to solve. Involving only one headlight strongly suggests a bad ground wire connection (likely the one at the affected headlight bucket), but the horn business is a twist I've never experienced.

 

To be honest, my friend did the change from old to used. I wanted to be their, but he said I didn't need to be so I didn't want to nag, so I don't know what he did. I actually wanted to be their because the guy selling me the used part sold it for 70$ and it included the throttle body. He said if I seperated the censor from the new body and only put the sensor on, and it didn't work, it would void the warrenty, but my friend didn't listen, and took it off anyway.He has experience as a mechanic, but I can't be sure if he knew the proper process. When I did the second change, from the used to the new I did it myself. That time I know I didn't do anything special, just screwed it on.

 

When I had the relay problem, did this reset something on the original tps. Is it possible the original one was never a problem.

 

What year is your Accent and which engine?

 

Its an 02, 1.5

 

Here is a thread on this forum where TPS adjust was discussed:

https://www.hyundaiforum.com/m_12563/tm.htm

Below is the TPS trouble shooting section from the Hyundai Service site for your car. You need to use a multimeter to measure voltage and resistance of the TPS. Fundementally, your computer is receiving the wrong information regarding the throttle position and cannot provide the correct fuel/air mixture to the engine.


2002 > G 1.5 SOHC > Fuel System

THROTTLE POSITION SENSOR (TPS)

The TP Sensor is a rotating type variable resistor that rotates with the throttle body's throttle shaft to sense the throttle valve angle. As the throttle shaft rotates, the throttle angle of the TP Sensor changes and the ECM detects the throttle valve opening based on the TPS output voltage.[/align]



CIRCUIT DIAGRAM



TROUBLESHOOTING HINTS[/align]

1.The TPS signal is important for the control of the automatic transaxle. Shift shock and other trouble may occur if the sensor is faulty.[/align]

2.If the idle condition or acceleration is abnormal, check the TPS connector. (When the TPS connector is not connected properly, the current data on HI-SCAN can show that the idle state remains off, although the accelerater pedal is released. This results in the improper idle or acceleration.)[/align]

3.Input voltage from throttle position sensor is below 0.1V or above 4.7V when ignition switch is turned on.[/align]

USING VOLTMETER[/align]

Check item[/align]

Check condition[/align]

Test specification[/align]

Throttle position sensor output voltage[/align]

(TP Sensor side connector No.1 or ECM harness side connector No.16)[/align]
At idle rpm[/align]0.25 ~ 0.8V[/align]
Wide open throttle[/align]4.0 ~ 4.8V[/align]

HARNESS INSPECTION PROCEDURES[/align]



SENSOR INSPECTION[/align]

1.Disconnect the throttle position sensor connector.[/align]
2.Measure the resistance between terminals 2 (sensor ground) and terminal 3 (sensor power).[/align]

[hr]0.7 ~ 3.0 kΩ[/align][hr]
3.Connect an analog ohmmeter between terminals 2 (sensor ground) and terminal 1 (sensor output).[/align]

4.Operate the throttle valve slowly from the idle position to the full open position, and check that the resistance changes smoothly in proportion with the throttle valve opening angle.[/align]

5.If the resistance is out of specification, or fails to change smoothly, replace the throttle position sensor.[/align]

[hr]Tightening torque[/align]Throttle position sensor :[/align]1.5 ~ 2.5 Nm (15 ~ 25 kg·cm, 1.1 ~ 1.8 lb·ft)[/align][hr]
[/align]

 

Thanks Ken. It sounds like my friend would have needed a manual for my car to do this properly, in order to know what ranges to look for, which probably means he just slapped it on like I did with the new one.

 

The basic things you need to measure are:

1) Make sure the sensor is receiving adequate voltage from the harness (4.7 to 5.2 VDC).

2) Adjust the output of the sensor at full throttle to 4.0 to 4.8 VDC.

3) Once you adjust the open throttle voltage, check the closed throttle voltage to see if it is between 0.25 and 0.80 VDC.

4) Repeat steps 2 and 3 until both settings are in tolerance.

At some point you will need to get the TPS error code in the computer reset. The old error will remain resident until it is cleared. Many parts stores will loan scanners to customers for this purpose.

Good luck.

 

I brought it to a dealership to do the work and they said it was precalicrated.
All I have to do is just screw it on. I called another dealership and they said
the same thing, so now I am confused. I drove it home from the dealership,
and there was no hesitation so I don't know what they might have done to
fix it, if anything,but now they said(contrary to what I said in my first post)
that a code 121 can be caused by a bad MAF.I was told it would be a
different code if it was the MAF.That's why I went ahead and bought the
TPS since the symptoms match the code They also said the sensor wasn't
completely on properly(a tiny gap on the bottom screw) which was stripped.
So I echanged the screws, because the top screw is easier to screw on,
and it looks like it is on perfect now. I will drive to work and seehow it runs.