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Possible but I doubt it. The code means the computer is not getting a signal back from the sensor. To test the sensor you would have checked for the reference voltage on the yellow wire, then check the resistance of the sensor with a meter. You probably don't have voltage going to the sensor, or else the harness is bad between the sensor and the computer. The return voltage is low at idle and goes up as the throttle is opened. ( I think )
• Powertrain Control Module Description for the 2.8L engine
• Powertrain Control Module Description for the 3.5L engine
Throttle Actuator Control (TAC) System
Throttle Actuator Control (TAC) Overview
The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle blade. This eliminates the need for a mechanical cable attachment from the accelerator pedal to the throttle body. This system also performs the cruise control functions as well.
The TAC system components include, but are not limited to the following:
• The accelerator pedal position (APP) sensors
• The throttle body
• The powertrain control module (PCM)
Each of these components interface together to ensure accurate calculations and control of the throttle position.
Accelerator Pedal Position (APP) Sensor
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The APP is 2 individual APP sensors within one housing. There are 2 separate signal, low reference, and 5-volt reference circuits. APP sensor 1 voltage increases as the accelerator pedal is depressed. APP sensor 2 voltage decreases as the accelerator pedal is depressed.
Throttle Body Assembly
The throttle body for the throttle actuator control (TAC) system is similar to a conventional throttle body with several exceptions. One exception being the use of a motor to control the throttle position instead of a mechanical cable. Another exception is the throttle position (TP) sensor. The TP sensor is mounted in the throttle body assembly. The TP sensor is 2 individual TP sensors within the throttle body assembly. Two separate signals, low reference, and 5-volt reference circuits are used to connect the TP sensors and the powertrain control module (PCM). TP sensor 2 signal voltage increases as the throttle opens. TP sensor 1 signal voltage decreases as the throttle opens.
Reduced Engine Power Mode
When the PCM detects a problem with the throttle actuator control (TAC) system the PCM enters one of the following Reduced Engine Power Modes:
• Acceleration Limiting--The control module will continue to use the accelerator pedal for throttle control, however the vehicle acceleration is limited.
• Limited Throttle Mode--The control module will continue to use the accelerator pedal for throttle control, however the maximum throttle opening is limited.
• Throttle Default Mode--The control module will turn OFF the throttle actuator.
• Forced Idle Mode--The control module will perform the following actions:
- Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned OFF.
- Ignore accelerator pedal input.
• Engine Shutdown Mode--The control module will disable fuel and de-energize the throttle actuator.
Have you had it checked for DTC'S - diagnostic trouble codes ?
The commanded throttle position (TP) is compared to the actual TP. Both values should be within a calibrated range of each other. The powertrain control module (PCM) continuously monitors the commanded and actual TPs. If the values are greater than the calibrated range, DTC P2176 sets.
The accelerator pedal position (APP) sensors 1 and 2 are located within the accelerator pedal assembly. Each sensor has the following circuits:
• A 5-volt reference circuit
• A low reference circuit
• A signal circuit
This provides the powertrain control module (PCM) with a signal voltage proportional to accelerator pedal movement. The APP sensor 1 signal voltage at rest position is near the low reference and increases as the pedal is actuated. The APP sensor 2 signal voltage at rest position is near the 5-volt reference and decreases as the pedal is actuated.
The throttle actuator control (TAC) assembly has 2 throttle position (TP) sensors mounted within the assembly. The powertrain control module (PCM) provides individual signal, ground, and 5-volt reference circuits to each sensor. Both sensors operate within a voltage range between 0.35-4.65 volts. When the throttle is opened from 0-100 percent, one sensor signal voltage increases while the other decreases. The signal circuit for TP sensor 1 is referenced to ground, and the signal circuit for TP sensor 2 is pulled up to 5 volts within the PCM.
What's this ? gaugesax out P0123 - Throttle Position (TP) Circuit High Input
The TP sensor circuit is monitored by the PCM for a high TP rotation angle (or voltage) input through the comprehensive component monitor (CCM). If during key ON engine OFF or key ON engine running the TP rotation angle (or voltage) changes above maximum calibrated limit, the test fails.
TP sensor not seated properly
TP circuit short to PWR
TP circuit short to ETCREF
SIG RTN circuit open to TP sensor
Damaged TP sensor
A TP PID (TP V PID) reading greater than 93% (4.65 volts) in key ON engine OFF, continuous memory or key ON engine running indicates a hard fault.
P0123 - ETC Throttle Position (TP1) sensor Circuit High Input
The ETC TP sensor 1 was flagged as fault status by the PCM indicating high voltage.
ETC TP1 sensor harness shorted to VREF
ETC TP1 sensor harness shorted to PWR
Damaged TP1 sensor
VREF circuit shorted to TP1 sensor
Drive vehicle, bring to a stop, turn key OFF. Start vehicle, run key ON engine running self-test at idle. Access KOER diagnostic trouble codes on scan tool.
P0193 - Fuel Rail Pressure Sensor Circuit High Input (FRP)
The comprehensive component monitor (CCM) monitors the FRP sensor circuit to the PCM for high voltage. If voltage were to fall below a calibrated limit and a calibrated amount of time during testing, the test will fail.
FRP signal shorted to VREF or VPWR.
FRP signal open (gasoline only)
Low fuel pressure (NG only)
Damaged FRP sensor.
High fuel pressure (caused by damaged fuel pressure regulator) NG.
A FRP PID value during KOER or KOEO less than 0.3 volts for gasoline or 0.5 volts for natural gas vehicles (NG) would indicate a hard fault.
P0340 - Camshaft Position (CMP) Sensor Circuit Malfunction (Bank 1)
The test fails when the PCM can no longer detect the signal from the CMP sensor on Bank 1.
CMP circuit open
CMP circuit short to GND
CMP circuit short to PWR
SIG RTN open (VR sensor)
CMP GND open (Hall effect sensor)
CMP misinstalled (Hall effect sensor)
Damaged CMP sensor shielding
Damaged CMP sensor
Harness routing, harness alterations, improper shielding, or electrical interference from other improperly functioning systems may have intermittent impact on the CMP signal.
TR Circuit Failure
TR circuits, indicating an invalid pattern in TR_D. Condition caused by a short to ground or an open in P/N, D, R, 2 or 1 circuits. Open in the taillamp ground circuit. This DTC can be set by an incorrectly adjusted TR sensor.
Increase in control pressure (harsh shifts). Defaults to D for an invalid position. MIL on.
Inspect the taillamp ground circuit. Go To Pinpoint Test C .
Some throttle position sensors are adjustable. Follow manufacturer's instructions.
On older engines, correct adjustment is crucial to proper system operation.
On newer engines, this is not as important because the computer uses whatever reading it takes at idle as base voltage (adaptive learn strategy).
Incorrect TP sensor adjustment may cause:
Inaccurate idle speed,
Engine stalling, and
Follow these steps to adjust a typical TP sensor:
Backprobe the TP sensor signal wire and connect a voltmeter from this wire to ground.
Turn on the ignition switch and observe the voltmeter reading with the throttle in the idle position.
If the TP sensor does not provide the specified voltage, loosen the TP sensor mounting bolts and rotate the sensor housing until the specified voltage is indicated on the voltmeter.
A TP Sensor with elongated slots for sensor adjustments. Courtesy of General Motors Corporation - Chevrolet Motor Division.
Hold the sensor in this position and tighten the mounting bolts to the specified torque.
Most throttle position sensors are made so that their adjustments are tamperproof. They have screws that are either soldered or staked.
To remove the switch, these might need to be drilled or filed off. After the new switch is installed and adjusted, the new mounting screws are restaked.
Improve the Fixya.com experience for everyone by voting! NOTE: In order to perform a meaningful diagnosis, it is necessary to utilize either a code scanner or code reader. A test light, ohmmeter, digital voltmeter, vacuum gauge and jumper wires may be required. You do not need any of the aforementioned items to inspect vacuum hoses, wiring, or disconnected plugs or adapters. All of these items can be borrowed from AutoZone -- FREE!
Before undertaking any repair or diagnostic work, be sure to inspect wiring for proper connection, burned or worn/chafed spots, and cuts.
Be sure to check hoses that are hard to see beneath the air cleaner, compressor, alternator, etc.
It sounds to me like your idle relief valve and/or the throttle position sensor is malfunctioning.
The throttle position sensor is used by your on-board computer to determine the amount of throttle demanded by the driver.
Detailed Explanation: The Throttle Position (TP) sensor is connected to the throttle shaft and is controlled by the throttle mechanism. A 5 volt reference signal is sent to the TP sensor from the ECM. As the throttle valve angle is changed (accelerator pedal moved), the resistance of the TP sensor also changes. At a closed throttle position, the resistance of the TP sensor is high, so the output voltage to the ECM will be low (approximately 0.5 volt). As the throttle plate opens, the resistance decreases so that, at wide open throttle, the output voltage should be approximately 5 volts. At closed throttle position, the voltage at the TP sensor should be less than 1.25 volts.
The idle air relief valve does a lot of good things but is a pain when not functioning.
• Regulates the amount of air entering the engine during idle.
• When not replaced, vehicle could experience high or low idle, engine dies at idle and/or severe high idle possibly causing internal engine damage and safety issues.
Please understand that these are mere suggestions and a comprehensive analysis requires a code scanner or code reader as stated above.
The steps I'm going to outline are the same as we use in my shop for hesitation, sag and stumble. Out of the box, I'd say that you have a problem with the fuel management system. However, there's a good chance that it's something simple and inexpensive like a clogged fuel filter or water in the fuel tank.
All of the tools required can be borrowed from AutoZone at NO COST!
•The sensors can be checked with an OBD-II code scanner borrowed from AutoZone. Pay special attention to an TP (Throttle Position) warnings. The sensor can be manually checked for binding or sticking.
•Check the Heated Oxygen Sensor (HO2S) found near the firewall and screwed into the exhaust manifold for signs of corrosion on the threads. That will cause a faulty ground.
•Check the fuel pressure with that fuel pressure gauge from AutoZone. You reading should be 40-45 PSI and holding steady.
•Contaminated fuel is a constant problem and if the pressure does not hold steady, replace the fuel filter.
•Make certain that the engine thermostat is functioning and is the correct temperature.
•Make certain that the alternator voltage output is not less than 9 volts nor more than 17 volts.
Here's a little general information that will assist you in comprehending the readouts from the code scanner. This is simply for your edification. You may be aware of all this but we've never done business before and all assumptions are off the table.
All the best,
With both codes pointing at TP sensor, I'd certainly take the time to replace it, as well as make sure connections to it are clean, and good. Chances are, you won't be able to take part back anyway. As far as exhaust goes, if it's leaking in the right places in may cause improper readings at sensors downstream, but if not obvious leak, I wouldn't be concentrating in that area right now.
Disconnect the throttle position (TP) sensor electrical
Remove the TP sensor attaching screws
Remove the TP sensor
Remove the TP sensor O-ring seal
Install the TP sensor O-ring seal (7) on the TP sensor (6).
Install the TP sensor on the throttle body with the throttle valve in
the closed position. Make sure the TP sensor lever lines up with the TP sensor
drive lever on the throttle shaft.
Notice: Use the correct fastener in the correct
location. Replacement fasteners must be the correct part number for that
application. Fasteners requiring replacement or fasteners requiring the use of
thread locking compound or sealant are identified in the service procedure. Do
not use paints, lubricants, or corrosion inhibitors on fasteners or fastener
joint surfaces unless specified. These coatings affect fastener torque and joint
clamping force and may damage the fastener. Use the correct tightening sequence
and specifications when installing fasteners in order to avoid damage to parts
Idle air control at base of throttle body. Passages could be plugged or idle hard stop needs adjusting.
Air Intake System Sensors
Air intake system sensors include a heated resistor-type mass air flow (MAF) sensor and throttle position (TP) sensor; both supply data to the powertrain control module (PCM). The PCM also monitors engine speed.
Air Intake System Control Devices
The idle air control (IAC) solenoid regulates idle speed by adjusting the amount of air allowed into the intake manifold. Adjustment is made by varying the duty cycle output by the powertrain control module (PCM). The PCM will increase the duty cycle for added mechanical or electrical loads. The IAC solenoid is combined with the fast idle control (FIC) solenoid which is turned on when the air conditioner is engaged to help compensate for the additional load. The IAC valve must be replaced as an assembly with the FIC solenoid.
Fast Idle Control (FIC) Solenoid
The fast idle control (FIC) solenoid (Figure 1) compensates for idle speed change caused by the operation of the air conditioner compressor. The FIC solenoid is controlled by the FIC relay. The FIC relay is energized when the air conditioner clutch is energized and the relay allows the FIC solenoid to turn on and let an additional volume of air into the intake manifold.
Figure 1: Fast Idle Control (FIC) Solenoid
Throttle Body (TB)
The throttle body (TB) controls the amount of air that flows into the engine through a single butterfly valve. The single butterfly valve opening is determined by the accelerator pedal. The TB is cast with an air bypass channel and houses several emission-related components for the powertrain control module (PCM).
Throttle Position Sensor (TP Sensor)
The throttle position (TP) sensor responds to the accelerator pedal movement. The TP sensor is a potentiometer that transforms the throttle plate opening angle into output voltage and sends the voltage signal to the powertrain control module (PCM). In addition, the sensor detects the opening and closing speed of the throttle plate and sends the voltage signal to the PCM. Also, the TP sensor is used to determine the air intake when the mass air flow (MAF) sensor fails. This mode of operation is called Fail Safe.
The TP sensor integrates the idle (IDL) switch within the housing. The IDL switch detects when the throttle plate is closed and an idle condition occurs. The PCM is supplied with this input signal.
Rough idling commonly comes from defective components of the electronic fuel injection system. You may start with fine tune adjustment of the idling speed using the idling speed adjustment port just above the TP sensor. If it will not help, try loosening the bolt of TP sensor, change the mounting angle and observe for any improvement. If doing this will not work, replace the TP sensor. If still the problem is present try cleaning or replacing the idle air control valve. The one with hose connection to the air intake pipe. If still it will not work, try replacing the MAF sensor just after the air filter. The last thing you may do if all of the things above will fail, have someone check your ECM.
Cleaning the PCV (positive crankcase ventilation) valve may help too. Why not start with this activity.