P2129 Throttle/Pedal Position Sensor/Switch “E” Circuit Intermittent
OBD-II Trouble Code Technical Description
Throttle/Pedal Position Sensor/Switch "E" Circuit Intermittent
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to all 1996-newer vehicles (Dodge, Chrysler, Hyundai, Jeep, Mazda, etc.). Although generic, the specific repair steps may vary depending on make/model.
In my own personal experience, I have found that a stored P2129 code means that the powertrain control module (PCM) has detected an intermittent malfunction in the circuit for the "E" throttle position sensor (TPS) circuit.
The TPS is typically a potentiometer type sensor that completes a five-volt reference circuit. The TPS is mechanically actuated using an extension of the throttle plate shaft or a specially designed tab on the sensor. As the throttle is opened and closed, contacts in the sensor are dragged across a circuit board, varying sensor resistance. As sensor resistance is changed, TPS circuit voltage fluctuates. The PCM recognizes these fluctuations as varying degrees of throttle plate actuation.
The PCM uses input voltage signals from the TPS to calculate fuel delivery and ignition timing. It also uses TPS input data to monitor intake air flow, exhaust oxygen content, exhaust gas recirculation (EGR) function, and engine load percentage.
If the PCM detects a certain number of intermittent or erratic signals from the TPS, over a set period of time, and under a programmed set of circumstances, a code P2129 will be stored and a malfunction indicator lamp (MIL) may be illuminated.
Severity & Symptoms
The TPS plays an important role in engine drivability, therefore a stored code P2129 should be addressed with some degree of urgency.
Symptoms of a P2129 code may include:
Causes
Possible causes for this engine code include:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.
I typically use a diagnostic scanner, a digital volt/ohmmeter (DVOM), and an accurate vehicle information source (ALL DATA DIY) to diagnose a code P2129.
A successful diagnosis usually begins with a visual inspection of all system related wiring and connectors. I also like to test the throttle plate for signs of carbon coking or damage. Repair or replace defective wiring or components as required, then recheck the throttle body and TPS.
Connect the scanner to the diagnostic connector; retrieve all stored trouble codes and write them down for future reference. I also keep any related freeze frame data. My notes are often helpful if the stored code proves to be intermittent. Next, I would clear the codes and test-drive the vehicle. Continue with the diagnosis if the code is reset. If it is not reset, the condition may need to worsen before a correct diagnosis can be made. Operate the vehicle normally until the PCM enters readiness mode or the code is reset.
Proceed by checking for technical service bulletins (TSB) that apply to the particular malfunction (and vehicle) in question by consulting your vehicle information source. If applicable, use the information contained in the appropriate TSB to help with your diagnosis. TSBs can be especially helpful when diagnosing an intermittent condition.
The scanner data stream may yield useful information regarding glitches and inconsistencies in the throttle position sensor. If you narrow the scanner data stream to display only pertinent data, you will get a more accurate data response.
If no glitches are detected, use the DVOM to test the TPS. Using the DVOM gives you access to live data if the appropriate test leads are connected to the ground and signal circuits. Watch the DVOM display while operating the throttle manually. Look for glitches in voltage as the throttle is actuated slowly from the closed position to wide open throttle. Voltage typically ranges from .5-volts at closed throttle to 4.5-volts at wide open throttle. If glitches or other inconsistencies are detected, suspect that the sensor being tested is defective or misadjusted.
Additional diagnostic notes:
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"Delete Error Code Permanently, Disable DTC Error Code Function for p2129 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p2129 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p2129.
