The P1508 error code, particularly in vehicles like the Porsche 996 Turbo, signals an issue within the engine’s torque comparison monitoring system. This code, identified as “Torque comparison function monitor — signal implausible,” suggests a discrepancy between the engine’s expected torque output and the actual torque being produced. Let’s delve into understanding this error and potential causes.
Essentially, the P1508 code arises when the Engine Control Unit (DME in Porsche terminology) detects an inconsistency in the torque comparison function. This function is designed to compare the torque demanded by the driver, signaled through the electronic gas (e-Gas) system, against the calculated engine load, which reflects the actual torque being generated. The system monitors the acceleration of the flywheel during each cylinder’s power stroke, looking for deviations that might indicate misfires or torque imbalances. While individual cylinder monitoring primarily triggers misfire errors, P1508 points to a broader issue with the overall torque comparison logic.
The factory manual for the 996 Turbo points directly to a “faulty DME control module” as a possible cause, even suggesting DME replacement without electrical testing, hinting at a software-related malfunction. The recommended procedure involves performing adaptation after a potential DME replacement, including an ignition cycle and fault memory reset.
However, in modified vehicles, especially those with increased performance, the Mass Air Flow Sensor (MAF) should also be considered as a potential culprit before assuming DME failure. Modified engines consume air at a significantly higher rate under hard acceleration, potentially exceeding the MAF sensor’s designed measurement range. This can lead to accelerated degradation of the MAF sensor and inaccurate readings. Therefore, a degraded MAF sensor might feed incorrect data into the DME, leading to a false P1508 reading.
To diagnose P1508 effectively, especially in modified cars, investigating the MAF sensor is crucial. Data logging intake temperature and air rate, particularly when the P1508 error appears, could reveal anomalous readings indicative of a failing MAF sensor. Analyzing these data logs before, during, and after the error occurrence can provide valuable insights and help pinpoint whether the MAF sensor or the DME is the root cause of the P1508 error code.
