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George H.
George H., Hyundai Technician
Category: Hyundai
Satisfied Customers: 2078
Experience:  Hyundai Gold certified, ASE Master tech 15+ years
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Thanks, getting a po121 code on my 2000 Hyundai elentra..

Customer Question

thanks, ***** ***** po121 code on my 2000 Hyundai elentra.. swapped out three different
JA: Just to clarify, what's the exact code? And have you tried to reset it?
Customer: I didn't mean to ssend..I changed out three different TPS and after clearing the code by
JA: Are you fixing your Elantra yourself? What have you tried so far?
Customer: changed the tps three times...does ok in n and p and so-so in drive but wants to try and stall in R getting the 121 code and switch
JA: Anything else you want the mechanic to know before I connect you?
Customer: what is the switch A? that comes with the code?
Submitted: 7 months ago.
Category: Hyundai
Expert:  david craig replied 7 months ago.

Hi Im David. thanks for visiting thee site. please allow m a few minutes to look up some information for you....thanks

Expert:  david craig replied 7 months ago.

well first off you can change the tps a thousand times and its not going to fix the issue. neither is the maf.

Customer: replied 7 months ago.
what do I need to do?
Expert:  david craig replied 7 months ago.

please allow me a few minutes so i can tell you what to do next. thank you.

Expert:  david craig replied 7 months ago.

P0121 Hyundai Description The throttle position sensor (TPS) responds to the accelerator pedal movement. This sensor is a kind of potentiometer which transforms the throttle position into output voltage, and emits the voltage signal to the Engine Control Module (ECM). In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM. Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor. This sensor controls engine operation such as fuel cut. On the other hand, the Wide open and closed throttle position switch, which is built into the throttle position sensor unit, is not used for engine control.

you will need to do a continuity check of the wiring between the tps and the acceleration sensor and then between each of those sensors and the ECM. not only check for continuity, but for high resistance shorts to ground and shorts to each other.

Customer: replied 7 months ago.
thanks but that's all greek to me.....
I didn't have this problem until I changed out the motor mounts and the transmission mount, I must have done something in the process that damaged something. the two additional tps came from the pick n pull, tried one and took it back and then tried another on along with the wiring that came with it but no luck....it seems a little hesitant when starting in drive and then I put it in N when stopping and it does ok but when backing in the driveway it wants to rev up and down or stumble like... it did shut off once on me in N.....it is an automatic....I crimped the newer to me tps connector wires to the original wires. would it have made any difference had I soldered them?
Expert:  david craig replied 7 months ago.

as long as the crimps were done correctly, it wouldnt have mattered. you really should have used a new oem sensor, but that just my opinion. you never know what you''re getting from a pic n pull when it comes to electronics. anyway. the above continuity procedure must be done to insure the integrity of the wiring unless you can physically find a damaged or pinched harness or wire.

Expert:  david craig replied 7 months ago.

I will be on throughout the day, but will be leaving for an appointment shortly.

Customer: replied 7 months ago.
thanks, ***** ***** give me a short lesson on how to check the continuity between the three mentioned above....also is the any reason that I have more trouble in reverse than drive?
Expert:  david craig replied 7 months ago.

reverse has a higher pressure than all the other forward gears

Expert:  david craig replied 7 months ago.

take your meter, select ohms. put one lead in the connector to the sensor you are checking(sensor disconnected) on the wire you are checking. put the other lead in the position of the ecm connector (disconnect connector)that correlates to the sensor wire you are checking. if the wire is good, the meter should read between 0.00-0.3

Customer: replied 7 months ago.
thanks, ***** ***** back from trying to take it to lunch, stalled at the first light, started back up but the tach
didn't work....never had a problem with the tach in 17 years.....it happened with the stall........mean anything???
Expert:  david craig replied 7 months ago.

does the tach move when trying to start? if not then the crank sensor is bad.

Customer: replied 7 months ago.
i'll go check. thanks
Expert:  david craig replied 7 months ago.

ill be gone fro about an hour. but will look for your answer

Customer: replied 7 months ago.
tach does not move when starting....or running....can this be the answer to all my problems?
by the way where is the crank position sensor located?
Expert:  david craig replied 7 months ago.

yes it can be, but to be sure you need to have a scan tool put on it and see if the computer is seeing rpms

Expert:  david craig replied 7 months ago.

if the computer isnt seeing rpms, then the cranks sensor will be the culprit. i dont want to tell you that just because the tach isnt working at all.

Expert:  david craig replied 7 months ago.

do you still need assistance?