We recently tackled a perplexing issue on an LS3 swapped Nissan 350z, encountering DTC P0068 and P0102, pointing towards a “Map/maf Throttle Position Correlation” problem. The setup involved a brand new LS3 crate engine with stock wiring and an E38 ECU, a common configuration for engine swaps. While the engine started, we immediately noticed throttle response problems and the check engine light illuminated, eventually throwing these specific codes.
The error codes P0068 (MAP/MAF – Throttle Position Correlation) and P0102 (Mass or Volume Air Flow “A” Circuit Low) indicated discrepancies in the readings between the Mass Air Flow (MAF) sensor, Manifold Absolute Pressure (MAP) sensor, and Throttle Position Sensor (TPS). These sensors are crucial for the Engine Control Unit (ECU) to accurately determine engine load and adjust fuel and air mixture for optimal performance.
Our initial troubleshooting steps included a thorough inspection of the wiring, despite it being a new harness designed for swaps. We checked all connectors for proper seating and any signs of damage. Suspecting a faulty Throttle Position Sensor, we even swapped it with a known good unit, but the problem persisted. We also verified the MAF sensor orientation and positioning within the intake system. Interestingly, the MAF sensor was reporting around 20 g/s at a 1000 RPM idle, which seemed within a reasonable range. The intake system utilized a Sikky 4″ tube, connected to the E38 ECU that was flashed with what was supposed to be a “stock” map from the engine supplier.
However, we quickly noticed anomalies in the ECU tuning. The idle RPM was consistently at 1000 RPM, unusually high for a truly stock LS3 ECU. Comparing the current ECU map to a factory LS3 Camaro map revealed significant differences, particularly in the MAF calibration tables. This raised a red flag concerning the ECU’s fuel and air calculations, especially given the 4″ intake tube. A larger diameter intake can alter airflow characteristics and potentially skew MAF sensor readings if the ECU is not correctly calibrated for it.
Further investigation into fuel trims revealed long trim values around -8% and short trim around -3% at idle with a 40 PSI fuel pressure regulator. This negative trim indicated the ECU was removing fuel, suggesting a rich condition. The stock LS3 fuel pressure regulator typically operates at a higher pressure, around 58 PSI. We suspected that with the potentially incorrect MAF calibration for the 4″ intake and the fuel pressure discrepancy, the ECU might be misinterpreting airflow, leading to the P0068 and P0102 codes. The “Throttle Position Correlation” error likely arises when the ECU detects inconsistencies between the expected airflow (based on throttle position and MAP readings) and the actual airflow measured by the MAF sensor.
Moving forward, our recommended course of action involves:
- ECU Map Verification and Recalibration: The immediate focus should be on the ECU map. It’s crucial to confirm if the MAF calibration table is indeed stock and suitable for a 4″ intake. Recalibrating the MAF table to match the 4″ intake diameter is likely necessary. Alternatively, flashing a known good, truly stock LS3 map for an E38 ECU could be a starting point.
- Fuel Pressure Check: Verify the fuel pressure regulator is operating at the correct specification for the LS3 engine. Incorrect fuel pressure can significantly impact fuel trims and overall engine performance, potentially contributing to sensor correlation errors.
- Intake System Review: Double-check the entire intake system for any leaks or obstructions that could affect airflow and MAF sensor readings.
Addressing the ECU calibration and fuel pressure are critical steps in resolving the P0068 and P0102 codes in this LS3 swap. Properly calibrating the ECU to the specific intake setup and ensuring correct fuel pressure will ensure accurate sensor readings and restore optimal engine operation.
