Tip & How-To about Mercedes-Benz E-Class

TPS faults and how to fix

1.3b) TPS Throttle Position Sensor faultsSymptoms of faulty TPS:
Associated OBD2 error codes DTCs: P0121 - P0123

  • Poor starting: The engine may start and then stall immediately.The engine may be encouraged to keep running by slowly pressing the accelerator pedal: pressing too quickly may again stall the engine.
  • Erratic/fast idling: The idle may be so erratic as to have some impact on the automatic gear shift characteristics and may actually prevent gear shifts. The engine idle speed may be increased above normal if the TPS fails to report that the throttle is closed. After the engine has been run at high speed the engine may take longer than is usual to return to idle as the ECU will not be able determine how quickly to shorten the injector cycles.
  • Engine hesitancy/ jump in revs: Engine may fail to respond quickly to the accelerator pedal input or may suddenly jump in revs inappropriate to pedal movement. When working properly the TPS should instantaneously signal the rapidly opened throttle position to the ECU. The speed of this signal is much quicker than any similar signal sent from Manifold Air Pressure (MAP) sensor or MAF/IATequivalent. The ECU responds by increasing the fuel injection volumes to match the rapid increase in air volume. If the TPS fails to send the correct signals, the engine will seem to "hesitate" as the throttle is applied as the ECU looks to the other (slower) sensors to determine engine status. A sudden blip of the accelerator at idle can stall the engine (see above - poor start) as the ECU reacts too slowly to increase the injection time to match the sudden intake of air.
  • Engine Misfire: Spurious, beyond normal range, signals from the TPS causes the ECU to set inappropriate fuel injection cycles resulting in misfire.Detected misfire leads to a check engine light(CEL); mal-function indicator lamp (MIL). Cylinders with misfire events detected by the knock sensor may be shut down (disable specific injectors) by the ECU to prevent engine damage.

Note: - With the TPS disconnected the ECU depends on the slower signals it receives from the Mass Air Sensor (MAS) and/or the Manifold Air Pressure (MAP) sensor along with feedback from the oxygen sensor to help regulate engine speed and fuel injection cycle.

How to check? The socket for electrical connection with the TPS has 3 pins, one for 'ground', one for 5 volts 'reference' and a third (generally the middle one) for 'signal' output. Back probe the signal pin in the connector to the TPS. Attach the positive lead of a voltmeter to the probe and measure the voltage output as the throttle plate is rotated. If working correctly the meter should show a voltage consistent with the throttle position from approximately 1 volt when closed and 5 volts when fully open. What is looked for is smooth voltage increase with throttle change.If there are drop outs in the throttle transition voltage signal or if there is no transition then the TPS is faulty.

How to fix? If the track is dirty causing drop outs, try cleaning it with residue-free electrical cleaningspray. If the track is worn it is perhaps easiest toreplace the complete device. In some instances it may be possible to adjust the location of the central mount of the TPS contact arm along the throttle shaft by a few millimeters and in the process cause a fresh concentric region of track to be used

NEXT 1.4) Idle Air/speed control valve

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2003 sta fe hyundai give code 121


P0121 HYUNDAI - Throttle/Pedal Position Sensor/Switch 'A' Circuit Range/Performance

Possible causes - Faulty throttle position sensor - Throttle position sensor harness is open or shorted - Throttle position sensor circuit poor electrical connection - Faulty Engine Control Module (ECM) What does this mean? When is the code detected? Malfunction is detected when an excessively low or high voltage from the sensor is sent to ECM. Possible symptoms - Engine Light ON (or Service Engine Soon Warning Light) 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.

Nov 20, 2016 | Hyundai Cars & Trucks

1 Answer

03 caravan showing codesP0123 and P0121. Can anyone help me with this. The van is not shifting gears properly. Thanks!


Hi there:
P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance

The Throttle position sensor is a potentiometer that measures the amount of throttle opening. As the throttle is opened, the reading (measured in volts) goes up. The powertrain control module (PCM) supplies a 5 Volt reference signal to the throttle position sensor (TPS) and usually a ground also. A general measurement is: at idle = .5 Volts; full throttle = 4.5 Volts. If the PCM detects that the throttle angle is greater or less than it should be for a specific RPM, it will set this code.


Symptoms of a P0121 trouble code could include:

Malfunction Indicator Lamp (MIL) illumination (Check Engine Light or Service Engine Soon light)
Intermittent stumble on acceleration or deceleration
Blows black smoke on acceleration
No start


A code P0121 may mean that one or more of the following has happened:
TPS has intermittent open or short internally
Harness is rubbing and causing an open or short in the wiring
Bad connection at the TPS
Bad PCM (less likely)
Water or corrosion in connector or sensor

Possible Solutions:
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.


P0123 Code - Throttle Position Sensor/Switch A Circuit High Input
A P0123 code means that the the car's computer has detected that the TPS (throttle position sensor) is reporting too high a voltage.


Symptoms may include:
Rough idle
High idle
Surging
other symptoms may also be present


A code P0123 may mean that one or more of the following has happened:
TPS not mounted securely
TPS circuit short to ground or another wire
Faulty TPS
Damaged computer (PCM)

Possible Solutions
If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, carefully inspect all wiring and connectors that lead to the TPS. More than likely the problem is with the TPS wiring. Check the voltage at the TPS (refer to a service manual for your vehicle for this specific information). If the voltage spikes or is too high (over 4.65 volts with key on, engine off), then that is indicative of a problem. Carefully trace each wire from the TPS wiring harness to check for breaks, rubbing against other components, etc.


Hope helps

Apr 19, 2012 | 2003 Dodge Caravan

3 Answers

p0121 generic throttle/pedal position sensor a circuit range/ performance


P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance Problem

The Throttle position sensor is a potentiometer that measures the amount of throttle opening. As the throttle is opened, the reading (measured in volts) goes up. The powertrain control module (PCM) supplies a 5 Volt reference signal to the throttle position sensor (TPS) and usually a ground also. A general measurement is: at idle = .5 Volts; full throttle = 4.5 Volts. If the PCM detects that the throttle angle is greater or less than it should be for a specific RPM, it will set this code.

Potential Symptoms: Symptoms of a P0121 trouble code could include:
Malfunction Indicator Lamp (MIL) illumination (Check Engine Light or Service Engine Soon light)
Intermittent stumble on acceleration or deceleration
Blows black smoke on acceleration
No start

Causes: A code P0121 may mean that one or more of the following has happened:
TPS has intermittent open or short internally
Harness is rubbing and causing an open or short in the wiring
Bad connection at the TPS
Bad PCM (less likely)
Water or corrosion in connector or sensor

Possible Solutions:
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.

Other TPS sensor and circuit related DTCs: P0120, P0122, P0123, P0124

May 01, 2011 | Volkswagen New Beetle Cars & Trucks

2 Answers

please can you give me the code of TPS of Chevrolet Epica 2004


There are 3 DTC codes related to the TPS....

1. P0121 - Throttle Position (TP) Sensor Performance

2. P0122 - Throttle Position (TP) Sensor Circuit Low Voltage

3. P0123 - Throttle Position (TP) Sensor Circuit High Voltage

If there is any further assistance, please let us know

Sep 27, 2010 | Chevrolet Chevy Cars & Trucks

3 Answers

2003 jeep wrangler trouble codes p0123, p0121, and p0152. What do they mean? Any help would be appreciated.


A code P0123 may mean that one or more of the following has happened:
  • TPS not mounted securely
  • TPS circuit short to ground or another wire
  • Faulty TPS
  • Damaged computer (PCM)
Possible Solutions If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, carefully inspect all wiring and connectors that lead to the TPS. More than likely the problem is with the TPS wiring. Check the voltage at the TPS (refer to a service manual for your vehicle for this specific information). If the voltage spikes or is too high (over 4.65 volts with key on, engine off), then that is indicative of a problem. Carefully trace each wire from the TPS wiring harness to check for breaks, rubbing against other components, etc.
A code P0121 may mean that one or more of the following has happened:
  • TPS has intermittent open or short internally
  • Harness is rubbing and causing an open or short in the wiring
  • Bad connection at the TPS
  • Bad PCM (less likely)
  • Water or corrosion in connector or sensor
Possible Solutions 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.
P0152 Oxygen Sensor Circuit High Voltage (Bank 2 Sensor 1)

Feb 16, 2010 | 2003 Jeep Wrangler

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