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Q: have a check engine light coming on. the code is a 121 and 122 low voltage on 2003 Hyundai Elantra

have changed the TPS senor, new computer, have had it checked by 5 different shops and the check engine light still come on the same code 121 122
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Check the wiring integrity and look even for possible rodent damage to the wiring. Check the following links,
Hyundai as a car manufacturer put a lot of free technical information and workshop manuals on line for Hyundai owners. Check out lots of great information. is not avaialble to open to the public. like myself... My 2003 hyundai Elantra with the 2.0 engine is reving at 3ooo rpm and will not come down. Has a manual throttle cable...Not seized... I have sprayed every single item with WD40 looking for a vaccum leak and lifted the car up to see if the intake bolts were loose and there tight.. No leaks found... TPs Maybe ? or IAC Motor Maybe ? Could you send the info to I;ve scanned it 4 times and 2 out of 4 times code comes up TPS,, and the other 2 times it says no problems found ...The one time after I cleared it it cam down to 1200 and the engine was hunting up and down drastically...attention Garry asap.. Thanks for now
for this code, you can
1. If you have access to a scan tool, see what the idle and WOT (wide open throttle) readings are for the TPS. Check if they're close to the specifications mentioned above. If not, then replace the TPS and re-check.

2. Check for an intermittent open or short in the TPS signal. To do that, you can't use a scan tool. You'll need an oscilliscope. The reason is because scan tools take samplings of many different readings over just one or two data lines and can miss an intermittent drop out. Hook up your oscilliscope and watch the signal. It should sweep up and down smoothly with no drop outs or spikes.

3. If no problems were noticed, perform a wiggle test. Do this by wiggling the connector and harness while watching the pattern. Does it drop out? If so, replace TPS and re-check.

4. If you have no TPS signal, check for 5 Volt reference at the connector. If it's present, check the ground circuit for open or shorts.

5. Make sure the signal circuit isn't 12V. It should never have battery voltage. If it does, trace circuit for short to voltage and repair.

6. Look for any water in the connector and replace TPS as necessary.

Pull out the alternator and have it checked for possible diodes broken or it could be faulty battery. Replace the battery or alternator when necessary.
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