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Discussion Starter · #1 ·
So my 2001 tj is throwing the codes po121 and po123... TPS high voltage codes. So I take my multimeter and check the ground, reference, and signal voltage. The ground is good. The reference is within spec. The signal is the same as the reference and goes down as I open throttle
5v closed
1.3v wot
What could be the problem because right now I'm stuck. Thanks
 

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Does the signal voltage vary smoothly each time in step with the control with repeated tests? The usual problem with the TPS is it wears inside and pieces of its variable resistor get in the way and cause erratic indications to the computer.
 

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Discussion Starter · #3 ·
No I believe the TPS is good. I'm
Testing the wires and the middle signal wire is not at the correct voltage. No wires are touching or broken so I'm stumped
 

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As a starting point why not just replace the TPS? If it's not the culprit you have a spare. They're $22 on rockauto.com.
I wouldn't touch an aftermarket sender/sensor, for critical components like sensors/senders/water pumps/starters etc. I'll stick with Mopar which isn't $22 for their TPS.

Here's just one reason why... it took me three aftermarket sensors from Autozone one Sunday before I finally got one that worked properly.
 

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Discussion Starter · #7 ·
As a starting point why not just replace the TPS? If it's not the culprit you have a spare. They're $22 on rockauto.com.
I wouldn't touch an aftermarket sender/sensor, for critical components like sensors/senders/water pumps/starters etc. I'll stick with Mopar which isn't $22 for their TPS.

Here's just one reason why... it took me three aftermarket sensors from Autozone one Sunday before I finally got one that worked properly.
It's not the sensor I already have a spare that has the same results it's the wires somewhere that are messed up except I don't know where to start
 

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P0121 -- TPS Voltage Does Not Agree With MAP -- TPS signal does not correlate to MAP sensor signal.

P0123 -- Throttle Position Sensor Voltage High -- Throttle position sensor input above the maximum acceptable voltage.

I’m not sure of the order in the connector but here are the wire colors & their function.

Orange is 5v supply
Black/light blue is sensor ground
Orange/dark blue is sensor signal

From the FSM

The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. This will vary in an approximate range of from .26 volts at minimum throttle opening (idle), to 4.49 volts at wide open throttle.

Doesn’t look like this is what you are seeing.
 

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Discussion Starter · #9 ·
P0121 -- TPS Voltage Does Not Agree With MAP -- TPS signal does not correlate to MAP sensor signal.

P0123 -- Throttle Position Sensor Voltage High -- Throttle position sensor input above the maximum acceptable voltage.

I’m not sure of the order in the connector but here are the wire colors & their function.

Orange is 5v supply
Black/light blue is sensor ground
Orange/dark blue is sensor signal

From the FSM

The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. This will vary in an approximate range of from .26 volts at minimum throttle opening (idle), to 4.49 volts at wide open throttle.

Doesn’t look like this is what you are seeing.

No I'm seeing the complete opposite with po121 and 123. The signal wire (middle one) has the same voltage as the reference wire. It also changes with the throttle only opposite. With the throttle wide open I get 1.3volts at the plug and with the throttle closed I get 5 volts
 

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Are you saying that the reference (5v) wire voltage drops with the signal voltage?

Also, do the wire colors match with the colors on the other side of the connector? It appears that the wire positions in the connectors may have changed between years.
 

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Discussion Starter · #11 ·
Are you saying that the reference (5v) wire voltage drops with the signal voltage?

Also, do the wire colors match with the colors on the other side of the connector? It appears that the wire positions in the connectors may have changed between years.
No the signal voltage drops with the throttle. This is when it is not plugged into the TPS but I am testing the prongs on the plug. The plug has 2 orange and a black going to it.
When I open the throttle the signal drops when according to spec it should start low and climb to around 5 volts which it is doing the opposite; starting high and going low.
 

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Why would the voltage drop in the harness when not plugged in to the sensor as when not plugged nothing changes when the throttle moves as far as the harness is concerned

If you mean voltage drops in sensor when not plugged in then I am still lost as sensor has no voltage to drop when not plugged in

I prefer to check a TPS measuring resistance between pins with it off the vehicle as the inside part is rotated
 

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Discussion Starter · #13 ·
Why would the voltage drop in the harness when not plugged in to the sensor as when not plugged nothing changes when the throttle moves as far as the harness is concerned

If you mean voltage drops in sensor when not plugged in then I am still lost as sensor has no voltage to drop when not plugged in

I prefer to check a TPS measuring resistance between pins with it off the vehicle as the inside part is rotated
What I am doing is turning the car to the on position not starting but just on. I go and ground one of the prongs on my multimeter and check the voltage supply for each of the electrodes on the plug. The ground and the power supply wire are within spec it's just the signal wire should be at .6 volts when it is actually matching the power supply wire at 5volts that is my confusion
 

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So you think the signal wire is shorted to the 5 volt supply wire

If I though that I would unplug the throttle sensor turn key to off and measure resistance signal wire to the power wire at the harness plug that you unplugged from the sensor

But to test the sensor remove it and measure resistance as you move the sensor thru its range of travel and observe for a smooth resistance change
 

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Discussion Starter · #15 ·
So you think the signal wire is shorted to the 5 volt supply wire

If I though that I would unplug the throttle sensor turn key to off and measure resistance signal wire to the power wire at the harness plug that you unplugged from the sensor

But to test the sensor remove it and measure resistance as you move the sensor thru its range of travel and observe for a smooth resistance change
Yeah I believe that may be it. I tested for continuity but I'm not sure if that was working great. I will test it as soon as I get off work
 

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I wouldn't touch an aftermarket sender/sensor, for critical components like sensors/senders/water pumps/starters etc. I'll stick with Mopar which isn't $22 for their TPS.

Here's just one reason why... it took me three aftermarket sensors from Autozone one Sunday before I finally got one that worked properly.
No it's $106. I just replaced a TPS on my jeep Monday with a pep boys model. Cost me $50 but worked like a charm and took all of 10 minutes. Call me a risk taker :)
 

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Mine was idling fast but no codes. Hooked up scanner and not TPS value wasn't changing with throttle position. Replaced it with one from Orielly's that worked great.
 

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Discussion Starter · #19 ·
If anyone was having the same problems... I switched the two outside wires and soldered them together. happy with no problems... Yet.
 
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