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Discussion Starter #1
2004 Santa Fe
2.7 6 Cyl 4WD 150k miles
Recently I started experiencing RPMs surging upon startup and driving before my engine warms up. The problem has gotten worse to where I push on the accelerator the RPMs jump to 2700 and the transmission feels like it disengages. My initial thought was the tranny was going bad and slipping. I checked the fluid level in the T and found it was maybe a half Qt. low. I topped it off, but this had no impact on the problem. On a side note, I am able to use the manual shifting feature on the "His and Hers" Shifter and drive the vehicle without any issue. Transmission works fine in manual. The surging RPMs which only occur in Automatic mode, triggered the CEL and I got a code of P0123 which is high side voltage on the Throttle Position Sensor. I replaced the gray TPS with a new black one. Upon startup the RPMS jumped to 3000 just sitting in Park. I disassembled and reinstalled figuring I had something bound in the throttle. After reassembly the idle went up to 2200, still no good! I reinstalled the original gray TPS and the RPMs, upon starting, RPMs were 1500 with the old sensor...still too high. I did reset the ECU twice during the process of putting in the new sensor and reinstalling the old sensor. Right now I found that when I disconnect the TPS electrical connector, the engine runs normal. It starts right up with the TPS totally disconnected and idles at 750 RPMs! It will not shift to 2nd gear though, when I try to drive it in Automatic Mode. I can however drive in Manual Mode and drive normal and shift right through the gears. Who needs automatic mode right?!!! I'm scratching my head on this one. Any suggestions would be greatly appreciated.
 

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It sounds to me like you may have a problem with the TPS ground circuit.

The trouble code says the TPS signal voltage is too high. The TPS sensor is a variable resistor with 5Volts on one end of the resistor track and ground on the opposite end. The sensor signal comes from a moving contact that moves across the resistor track, so the output will be between ground or 0V (throttle closed) and 5V (throttle fully open). If the sensor ground has a high resistance or is open circuit the signal voltage will never get to 0V when the throttle is closed. This would cause the P0123 code to be set.

You can check the sensor ground by carrying out a voltage drop test using a voltmeter. With the ignition on, connect the red meter probe to the sensor ground wire by back probing the sensor connector. You need to test with the sensor connected so there is current flowing in the circuit. Connect the black meter probe to battery negative terminal. Monitor the voltage on the meter while slowly opening and closing the throttle. The voltage should remain < 0.2V (200mV)

Regards.

Scott.
 

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Discussion Starter #3
Update. I reset the codes and the CEL went off when I disconnected the battery. I installed the new TPS and removed and thoroughly cleaned the Idle Control Valve. The CEL has not relit since resetting and I drove over 850 miles this last weekend! My problem right now is the RPMs at idle in Park will rev to 2200. Once I put it in Drive the RPMs drop below 700. The 2nd issue is with the transmission not wanting to shift to the next higher gear until the RPMs reach 4000. If I take my foot off the accelerator at about 33-35k RPMs the Tranny will shift and the RPMs drop to 200 as this happens and I can resume accelerating. and letting off to get the earlier shift point.


It seems that replacing the Throttle Pos Sensor has changed the problem. I have a new issue now with the RPMs at idel being too high and the transmission shift points being at too high an RPM.
 

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With the car running, listen around your engine compartment for a vacuum leak. 1 damaged vacuum line can cause weird surging issues.
 

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Discussion Starter #5
Problem Solved! Doh! When I replaced the TPS, I incorrectly twisted the fingers which protrude off the back of the sensor and in effect telling the computer the throttle was engaged/turned about 15 percent! The fingers sticking off the back of the sensor both should sit above the mating actuators, not one above and one below like I thought. Pay attention to their position when you remove the old sensor and install the replacement in the same position.


PS
I still occasionally have to pull the positive (+) cable off the battery when the tranny starts slipping. It's not the transmission it's the sensors!
 

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Problem Solved! Doh! When I replaced the TPS, I incorrectly twisted the fingers which protrude off the back of the sensor and in effect telling the computer the throttle was engaged/turned about 15 percent! The fingers sticking off the back of the sensor both should sit above the mating actuators, not one above and one below like I thought. Pay attention to their position when you remove the old sensor and install the replacement in the same position.


PS
I still occasionally have to pull the positive (+) cable off the battery when the tranny starts slipping. It's not the transmission it's the sensors!

Is there anyway you could post a picture of the tps sensor you used?
 
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