TPS voltage readings

I recommend you test the tps according to procedure below. Especially step 8. Suspect you will see drop outs in the voltage, which indicate sensor is worn out.
Operation

The Throttle Position Sensor (TPS) is mounted to the side of the throttle body and connects to the throttle blade shaft. The TPS is a variable resistor that provides the PCM with an input signal (voltage). The signal represents throttle blade position. As the position of the throttle blade changes, the resistance of the TPS changes.
The PCM supplies about 5 volts of DC current to the TPS. The TPS output voltage (input signal to the PCM) represents throttle blade position. The TPS output voltage to the PCM varies from about 0.5 volt at idle to a maximum of 4.0 volts at wide open throttle. The PCM uses the TPS input, and other sensor input, to determine current engine operating conditions. The PCM also adjusts fuel injector pulse width and ignition timing based on these inputs.
Testing

In order to perform a complete test of the TPS and related circuits, you must use a DRB or equivalent scan tool, and follow the manufacturers directions. To check the Throttle Position Sensor (TPS) only, proceed with the following tests.

1. Visually check the connector, making sure it is attached properly and that all of the terminals are straight, tight and free of corrosion.
2. The TPS can be tested using a digital ohmmeter. The center terminal of the sensor supplies the output voltage. The outer terminal with the violet/white wire is the 5-volt supply terminal and the black/light blue wire is the sensor ground terminal.
3. Connect the DVOM between the center terminal and sensor ground.
4. With the ignition key to the ON position and the engine OFF, check the output voltage at the center terminal wire of the connector.
5. Check the output voltage at idle and at Wide Open Throttle (WOT):
6. For 1996 vehicles at idle, the TPS output voltage should be greater than 0.35 volt (0.4 volt for the 2.4L engine). At WOT, the output voltage should be less than 4.5 volts (3.8 volts for the 2.4L engine).
7. For 1997 and later vehicles at idle, the TPS output voltage should be about 0.38-1.20 volts. At WOT, the output voltage should be about 3.1-4.4 volts.
8. The output voltage should gradually increase as the throttle plate moves slowly from idle to WOT.
9. If voltage measures outside these values, replace the TPS.
10. Before replacing the TPS, check for spread terminals and also inspect the PCM connections.

I found this picture, if that is correct? Probably a three wire connector, ref voltage--ground--signal. I did see another picture, I wasn't sure? This picture said dfi.

They are easier to test on the car 3 wires 1) 5 volt reference 1) signal return (testing this wire) last wire is ground. place + lead of a volt meter on the signal return wire with key on engine off negative lead on block or battery resting closed throttle should .3 to .8 volts slowly increase throttle opening and watch meter it should increase without voltage ever going lower E.G 1.0,1.1,1.2,1.3,.09,1.5 the .09 is a drop sensor bad this should continue to wide open throttle with a ending reading of 4.95 and above voltage. rdo this several times to catch a glitch.

The 3 wire Throttle Position Sensor (TPS) is mounted on the throttle body and is connected to the throttle blade.
The TPS is a 3wire variable resistor that provides the Powertrain Control Module (PCM) with an input signal (voltage) that represents the throttle blade position of the throttle body. The sensor is connected to the throttle blade shaft. As the position of the throttle blade changes, the resistance (output voltage) of the TPS changes.
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. Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. In response to engine operating conditions, the PCM will adjust fuel injector pulse width and ignition timing.
The PCM needs to identify the actions and position of the throttle blade at all times. This information is needed to assist in performing the following calculations:

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• HOME
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• 2001 JEEP GRAND CHEROKEE 4WD 4.0L MFI 6CYL REPAIR GUIDE
• ENGINE PERFORMANCE & EMISSION CONTROLS
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• THROTTLE POSITION SENSOR

Cherokee, Grand Cherokee, 1999-2005
Throttle Position Sensor

• OPERATION
• REMOVAL & INSTALLATION

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Operation

The 3 wire Throttle Position Sensor (TPS) is mounted on the throttle body and is connected to the throttle blade.
The TPS is a 3wire variable resistor that provides the Powertrain Control Module (PCM) with an input signal (voltage) that represents the throttle blade position of the throttle body. The sensor is connected to the throttle blade shaft. As the position of the throttle blade changes, the resistance (output voltage) of the TPS changes.
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. Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. In response to engine operating conditions, the PCM will adjust fuel injector pulse width and ignition timing.
The PCM needs to identify the actions and position of the throttle blade at all times. This information is needed to assist in performing the following calculations:


Ignition timing advance Fuel injection pulse-width Idle (learned value or minimum TPS) Off-idle (0.06 volt) Wide Open Throttle (WOT) open loop (2.608 volts above learned idle voltage) Deceleration fuel lean out Fuel cutoff during cranking at WOT (2.608 volts above learned idle voltage) A/C WOT cutoff (certain automatic transmissions only)

Removal & Installation

3.7L & 4.0L

1. Disconnect TPS electrical connector.
2. Remove TPS mounting screws.
3. Remove TPS.

To Install:
The TPS is mounted to the throttle body. The throttle shaft end of throttle body slides into a socket in the TPS. The TPS must be installed so that it can be rotated a few degrees. (If sensor will not rotate, install sensor with throttle shaft on other side of socket tangs). The TPS will be under slight tension when rotated.

1. Install TPS and retaining screws.
2. Tighten screws to 7 Nm (60 inch lbs.) torque.
3. Connect TPS electrical connector to TPS.
4. Manually operate throttle (by hand) to check for any TPS binding before starting engine.

4.7L

1. Remove air duct and air resonator box at throttle body.
2. Disconnect TPS electrical connector.
3. Remove two TPS mounting bolts (screws).
4. Remove TPS from throttle body.

To Install:
The throttle shaft end of throttle body slides into a socket in TPS. The TPS must be installed so that it can be rotated a few degrees. If sensor will not rotate, install sensor with throttle shaft on other side of socket tangs. The TPS will be under slight tension when rotated.

1. Install TPS and two retaining bolts.
2. Tighten bolts to 7 Nm (60 inch lbs.) torque.
3. Manually operate throttle control lever by hand to check for any binding of TPS.
4. Connect TPS electrical connector to TPS.
5. Install air duct/air box to throttle body.

Hope this helps

Can you send us exactly the OBD Codes - Mercury Diagnostic Trouble Codes that Autozone find there? With this code number could send other details.

Keep in touch.

this is an obd2 trouble code table, it can help you understand the meaning of code.
and for p0120
the Causes:
Sticking throttle return spring
MAP or TPS connector corrosion
Misrouted harness causing chafing
Bad TPS
Bad PCM
Possible Solutions:
If you have access to a scan tool, with KOEO (Key on engine off) observe the TPS voltage. With throttle closed, voltage should be about .45 volts. It should gradually sweep upwards to approximately 4.5 to 5 volts as you depress the throttle. Sometimes only a scope can capture an intermittent glitch in the TPS signal voltage. If you notice a glitch in the TPS sweep voltage, replace the TPS.
NOTE: Some TPS sensors require fine adjustment. If you aren't comfortable with using a DVOM (Digital Volt Ohm meter) to adjust the new TPS, then it's best to take the vehicle to a shop. If the voltage is not .45 volts (+or- .3 volts or so) with the throttle closed or if the reading is "stuck" then unplug the TPS connector. With KOEO check for 5 volts reference voltage present at the connector and a good ground. You can check the signal circuit for continuity by jumping a fused wire between the ground circuit of the TPS connector and the signal circuit. If the TPS reading on the scan tool now reads zero, then replace the TPS. However if that doesn't change the reading to zero, then check for an open or a short on the signal wire and if none is found, suspect a bad PCM. If manipulating the TPS wiring harness causes any change in idle, then suspect bad TPS.

Symptoms Symptoms of a P0105 check engine light code may include:

• Poor running engine
• Engine runs rich
• Engine won't idle
• Engine backfires through tailpipe
• Engine misfire under load or at idle
• MIL (Malfunction Indicator Lamp) illumination
• In some extreme cases there may be no symptoms other than MIL illumination

Causes A P0105 DTC could be caused by:

• MAP sensor vacuum hose disconnected or plugged
• Bad MAP Sensor
  
• Bad TPS
• Damaged or problematic MAP sensor connector
• Damaged or problematic TPS connector
• Damaged wiring
• Short to reference voltage on signal circuit of MAP Sensor
  
• Loss of ground to MAP sensor or TPS
• Open on signal circuit of MAP sensor
• Bad PCM

Possible Solutions Using a scanner or code reader, turn the ignition on and engine OFF; what does the MAP sensor voltage read? It should be about 4 Volts for sea level. If you are at a higher altitude, it should decrease about half a volt or so for each 1,000 ft. of altitude (this will vary from model to model) Or if you have a separate MAF (Mass air flow) sensor on your vehicle, they are usually equipped with a Barometric pressure reading. If so, the Baro reading should match the MAP reading (they both measure ambient air pressure). If they're roughly equal, then, check for Freeze Frame data of the MAP sensor (if available).
NOTE: Freeze Frame data is the PCM recording a fault when it happens. It captures the readings of the various PIDS (parameter identifiers)available to troubleshoot what happened. It's like a recording of the problem as it happened. At idle a typical MAP sensor Voltage reading should be about a volt, and at WOT (wide open throttle) it should approach 4.5 to 5 Volts. As for the TPS, at idle, the voltage reading is about 1 Volt or less. As the throttle is opened the reading will increase to 4.5 Volts at WOT. Do the two readings make sense? For example, if the TPS reading on Freeze Frame data shows 2.5 Volts (indicating partial throttle) does the MAP sensor indicate a reading that isn't at either extreme? Using the Freeze Frame data (if available) compare the MAP reading to the TPS when the problem occurred. This can help you identify what happened
If you have no access to Freeze Frame data then check if the MAP sensor voltage changes when you apply vacuum to it. You can do this by mouth or a vacuum pump. The voltage should increase as you apply vacuum. If the reading doesn't change as you apply vacuum, make sure there are no obstructions in the hose to the sensor. If the hose is clear, the MAP sensor is usually bad, but it doesn't rule out the following from causing the problem: Does the MAP sensor appear to be stuck at less than .5 Volts? Then:
NOTE: This code shouldn't set if the MAP is stuck at extremely low voltage, however, I'm adding it in because there's no way to know for certain for which vehicles a low voltage condition may set a P0105

1. Inspect the wiring harness and MAP sensor connector. Repair any damage
2. Unplug the MAP sensor connector. Also, at the PCM connector, remove the MAP sensor signal wire and check for continuity to the MAP sensor connector. If there is infinite resistance, then repair open in MAP signal circuit. If the signal wire has continuity to the MAP sensor connector, then check for 5 volt reference voltage to the connector and a good ground. If both are present, then re-install all removed wiring and replace the MAP sensor.

Does the MAP sensor appear to be stuck at full 4.5 voltage? Then:

1. Inspect the wiring harness for damage. Repair as needed
2. Remove the MAP sensor signal wire from the PCM connector. With a voltmeter measure the voltage with KEY ON ENGINE OFF. Is there 4.5 Volts? If so, unplug the MAP sensor and recheck. If it is still present, then repair short between the signal wire and 5 volt reference wire.
3. If unplugging the MAP sensor causes the voltage to disappear, check that the ground is intact. If it is, then replace the MAP sensor due to internal short.

The error is indicating that the Throttle Position Sensor (TPS) is out of the normal range with respect to the Idle Speed Control (ISC). Try something really simple and inexpensive first by removing the air ducting between the air filter box and the throttle body. Clean the throttle body interior and throttle plate with a cloth sprayed with WD40. Turn the throttle plate by pushing it at the top with your fingers and clean the throttle throat behind the plate as best you can. Reassemble the ducting and ensure that there are no air leaks at the junctions and no splits. Turn the key to position 2 (engine not running) and depress the accelerator pedal to the floor and then back up again. Start the car and nine times out of ten that should fix it. The TPS measures the opening angle of the throttle plate. The TPS is device consisting of a circular carbon track with a slider, corresponding to the throttle plate, sweeping along it. It as three wires to it, two to provide the 0 to 5 volt range along the length of the carbon track and the third to measure the voltage at the contact point of the slider. To check the TPS measure the voltage of the middle pin of the connector when the ignition is at position 2 (engine off) as you push the throttle plate open and closed by pressing on the accelerator pedal. The voltage should alter in a smooth continuous way. Any drop outs of signal indicate a worn carbon track and the TPS should be replaced.

Check the TPS (Throttle position sensor) wire lead and replace the TPS if any signs of damage or failure.

The Throttle Position Sensor (TPS) is used to send input signals to the Powertrain Control Module (PCM) to indicate the current angle of the throttle blade.

Theory/Operation:
This sensor is a variable resistor that has a 5 volt reference signal applied to it by the PCM. The TPS sends signals back to the PCM in the range of approximately 1 to 4 volts, depending upon the throttle shaft angle. The PCM uses these input voltages to determine the current position of the throttle.
The PCM uses the voltage signals from the TPS and other input sensors to determine the proper air/fuel mixture and ignition timing for certain operating conditions. Some of these operating conditions are: acceleration, deceleration, idle, and wide open throttle.


Typical Readings:
An input voltage of approximately 1 volt indicates a minimum throttle opening, idle, or deceleration condition. An input voltage of approximately 2 volts indicates a cruise or light acceleration condition. An input voltage of approximately 4 volts would indicate a maximum throttle opening or wide open throttle condition.
NOTE: The following procedure tests the TPS only.

1. The TPS can be tested with an analog voltmeter. The center terminal of the TPS is the output terminal.
2. With the ignition key in the ON position, check the TPS output voltage at the center terminal wire of the connector. Check this at idle (throttle plate closed), and at wide open throttle (WOT).
   • At idle, TPS output voltage should be approximately one volt. The output voltage should increase gradually as the throttle plate is slowly opened from idle to WOT.
   • At wide open throttle, TPS output should be approximately 4.5 volts.

As always, check the service manual for the proper procedures and specifications for your particular vehicle.

Thank you using Fixya and good luck.

"TPS" is your throttle position sensor located on the right side of your throttle body (if you are facing your engine) the function of the tps is to send imput to your pcm (power control module) by the movement of the throttle plate at idle/part throttle/wide open. the pcm will adjust air/fuel mix/egr functio/timing of spark based on tps imput by way of voltage signals. you can check for a bad tps sensor by using a voltmeter and back probing the tps connector. there are 3 wires with the connector tange facing up, the 3 wires are sensor ground (the wire closest to you) the middle wire is the sensor signal wire and the wire furthest away from you is the 5v supply wire. turn ign key to "on" (do not start engine) voltage should be between 0.2-1.4v with probes still inserted into the plug, slowly turn throttle pulley toward wide open throttle, youe readings should slowly rise to about 4.5v - IF NO VOLTAGE PRESENT- check wiring harness for supply voltage (around 5v) ground (0.3v) if both supply voltage and ground voltage present AND no output voltage tps FAULTY TPS. remove/replace tps. if voltage values exist, but are less than what they should be, look for problem with wiring harness, or bad pcm. my other thoughts are partially plugged fuel filter/pressure sensor, or a vacuum leak gremlin somewhere.