The following chronicles troubleshooting steps taken to resolve a persistent EPC (Electronic Power Control) fault and accompanying camshaft position actuator fault on a vehicle, potentially related to a Unitronic intake upgrade. Initial attempts to resolve the issue, including reverting accelerator settings to stock and installing a Unitronic full intake kit, proved unsuccessful.
Problem Description and Initial Attempts
The primary issue presents as an EPC fault triggered under high engine load, specifically during aggressive acceleration scenarios such as highway passing. When the fault occurs, the engine abruptly loses power, the clutches disengage, and the engine reverts to a rough idle with no throttle response. Restarting the engine immediately clears the fault, allowing normal operation until the scenario is repeated.
Initially, a non-stock accelerator response setting was suspected. Reverting this setting to the factory default did not resolve the problem. Subsequently, the factory intake system was replaced with a Unitronic full intake kit, also without success. A dealership inspection and attempted repair involving cam adjuster connectors also failed to eliminate the fault.
Dealership Diagnosis and Continued Issues
The dealership, after having the vehicle for several days, believed they had isolated the problem to the cam adjuster connectors. Their diagnosis focused on a camshaft fault that consistently appeared a few seconds after the initial throttle body warning (TBW) fault during deceleration. Despite their intervention, the EPC fault continues to occur under high load conditions, typically around 80% throttle or higher.
Error Codes and Their Interpretation
The following error codes were retrieved using VCDS (Vag-Com Diagnostic System):
15138 - Control Module Malfunction - DBW Throttle Monitoring P1388 00 [00100000] - - Intermittent - Not Confirmed - Tested Since Memory Clear
... (Freeze Frame Data) ...
15396 - Cam Adjustment Actuator A; Cylinder 2 P11A6 00 [01100000] - Implausible Signal Intermittent - Not Confirmed - Tested Since Memory Clear
... (Freeze Frame Data) ...The P1388 code indicates a malfunction within the drive-by-wire (DBW) throttle monitoring system. This suggests a potential issue with the throttle pedal, throttle body, or the wiring and connections between these components. The P11A6 code points to an implausible signal from the camshaft adjustment actuator on cylinder 2. This could indicate a faulty actuator, wiring issue, or a problem with the camshaft position sensor itself. The near simultaneous occurrence of these faults suggests a potential correlation. It’s possible the camshaft position actuator fault is a secondary symptom triggered by the initial throttle control issue.
Next Steps and Potential Solutions
Given the persistent nature of the fault and the unsuccessful attempts at resolution, the next logical step involves consultation with a knowledgeable tuner specializing in Volkswagen/Audi vehicles in the Atlanta area. A tuner experienced with Unitronic products and VCDS diagnostics might possess the expertise to pinpoint the root cause. Possible areas of investigation include:
- Thorough inspection of wiring harnesses and connectors: Focusing on the throttle body, camshaft actuators, and related sensors for damage, corrosion, or loose connections.
- Testing of the throttle body and camshaft position actuators: Using VCDS to perform output tests and monitor live data to identify any anomalies.
- Evaluation of the ECU (Engine Control Unit) software: Checking for any potential conflicts between the Unitronic intake and the current ECU mapping. A custom tune or software update might be necessary to optimize performance and resolve the issue.
Further diagnostic steps guided by a specialist are required to definitively resolve the EPC and camshaft faults and ensure safe and reliable vehicle operation.
