DBW Pedal P2138 Fault with SC430 Pedal on 1JZ Swap - Replace with 350Z Pedal Kit

Electricalintermediate✓ OP Confirmed

Problem

After installing a 1JZ swap with Haltech 2500 ECU, Bosch DBW throttle body, and SC430 DBW accelerator pedal, the pedal would not calibrate in Haltech NSP software. A P2138 code (accelerator pedal position sensor correlation error) was thrown every time calibration was attempted, and the DBW system would disable itself. Releasing the pedal after pressing it would immediately trigger the fault.

P2138 fault code (APP sensor correlation error) in Haltech ECUDBW disabled fault codePedal fails calibration in Haltech NSP software every timeAPP1 reads 0.76V unpressed to 4.83V pressedAPP2 reads 1.5V unpressed to 5V pressed (maxing out the sensor voltage)Fault triggers when releasing the pedal after pressing itIssue reproduced with two separate SC430 pedals with identical readings

Root Cause

The SC430 DBW accelerator pedal's APP2 sensor was maxing out at 5V when fully pressed, which exceeds the acceptable voltage range for proper APP1/APP2 correlation. The Haltech ECU expects the two APP signals to maintain a specific ratio/correlation throughout the pedal travel. With APP2 hitting 5V (essentially the same as the reference voltage), the ECU detected a sensor correlation fault. The SC430 pedal's sensor travel range was incompatible with the mounting geometry and the ECU's expected voltage curves, even after attempting pedal stop adjustments and verifying correct wiring.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted February 2026 on SupraForums.com