Owner's Problem Description
The owner reports that after driving for a while, the electronic throttle control light activates, followed by the electronic stability program light. This issue occurs regardless of driving duration. The vehicle was taken to a Dodge dealer, where the MAP sensor was replaced, but the problem persists, indicating a deeper issue within the throttle control system. Currently, the vehicle continues to exhibit these warning lights intermittently, affecting drivability.
Professional Technical Analysis
The 2007 Dodge Magnum, featuring a V6 engine with an approximate mileage of 90,000 miles, is experiencing recurrent issues with the electronic throttle control system. The symptoms include the activation of the electronic throttle control light and the electronic stability program light. Diagnostic trouble codes retrieved include P2173, indicating high airflow due to a vacuum leak, P2638, which suggests a torque management feedback signal performance issue, and C121C, indicating a torque request signal denial. These codes point towards potential underlying issues within the throttle body assembly or related sensors. The MAP sensor was replaced, but this did not resolve the issue, suggesting that further investigation is needed into the throttle position sensor (TPS), the electronic throttle body assembly itself, and vacuum integrity within the intake manifold. Current vehicle conditions indicate the possibility of reduced engine performance and safety concerns due to erratic throttle response. The vehicle's electrical systems should also be assessed, as voltage irregularities or poor connections could exacerbate these problems. Ensuring that the throttle body and associated wiring are in good condition is crucial for proper vehicle operation, as any faults here can lead to cascading failures affecting the PCM and stability control systems.
Possible Causes
Most common causes (ordered by frequency):
- Throttle Position Sensor (TPS) failure: The TPS may be providing incorrect readings to the PCM, causing erratic throttle control. This component typically exhibits resistance values between 0.5-4.5V depending on throttle position. If the TPS fails, it can lead to codes such as P2173 due to perceived high airflow. Testing should involve verifying voltage outputs at various throttle positions. - Intermittent throttle response issues, erratic engine performance, potential stored codes related to TPS malfunction.
- Vacuum leak in intake manifold: A vacuum leak can cause the MAP sensor to read higher airflow, resulting in P2173. Inspecting all vacuum hoses and the intake manifold for cracks or disconnections is essential. A smoke test can be employed to identify leaks effectively. - High idle RPMs, hissing sounds from the engine bay, potential stored codes related to vacuum integrity.
- Electronic Throttle Body (ETB) malfunction: The ETB can exhibit failure patterns, especially in earlier models, leading to erratic throttle response and triggering stability control warnings. This could stem from internal motor failure or carbon buildup. An ETB cleaning or replacement may be necessary. - Erratic throttle response, warning lights activation, potential stored codes related to ETB performance.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Comprehensive OBD-II Scan: Utilize a professional OBD-II scanner or the GeekOBD APP to retrieve all stored and pending codes. Pay special attention to freeze frame data, which can provide crucial insights into vehicle behavior at the time of the fault occurrence. The presence of P2173, P2638, and C121C will guide the diagnostic focus.
- STEP 2 - Visual Inspection of the Throttle Body and Sensors: Conduct a thorough visual inspection of the electronic throttle body and associated wiring harness. Look for signs of carbon buildup on the throttle plate, damaged connectors, or frayed wires. Ensure all vacuum lines are connected and intact. If necessary, clean the throttle body using an appropriate cleaner.
- STEP 3 - Throttle Position Sensor Testing: Using a multimeter, check the TPS voltage output at idle and wide-open throttle (WOT). The voltage should range approximately between 0.5V at idle and 4.5V at WOT. If the readings are out of spec, consider replacing the TPS. Also, verify the integrity of the wiring harness leading to the TPS.
- STEP 4 - Conduct a Vacuum Leak Test: Perform a smoke test to identify any vacuum leaks in the intake system. This test will help pinpoint any hidden leaks that could be affecting the MAP sensor readings and triggering the P2173 code. Repair any identified leaks.
