The Gpec2 engine control module, found in various Chrysler vehicles, can present unique tuning challenges. This article delves into a persistent issue with a 2013 Ram 1500 4×2 equipped with a GPEC2, specifically focusing on inactive short-term fuel trims (STFTs) on Bank 2. We’ll explore the vehicle’s history, the problem’s symptoms, diagnostic steps taken, and potential solutions for resolving this GPEC2-related issue.
A History of Modifications and Tuning Adjustments on the GPEC2
This Ram 1500 has undergone significant modifications, including a 6.4L SRT engine swap with upgraded camshaft, intake, and exhaust. The transmission was also upgraded from a 65RFE to an 8HP70 using a Sound German Automotive (SGA) harness and computer. This involved numerous tuning revisions using DiabloSport and HP Tuners (HPT) software, including a custom HemiFever tune and adjustments by multiple tuners. Notably, the original 65RFE transmission failed twice, necessitating rebuilds and further tuning adjustments to accommodate the 8HP70 swap. The current tune was developed by a reputable HPT tuner and delivers satisfactory performance, but persistent inactivity in Bank 2 STFTs remains.
The Persistent Issue: Bank 2 STFTs Remain at Zero
Despite the truck running well overall, the STFTs for Bank 2 consistently read zero, indicating a lack of fuel adjustment based on oxygen sensor feedback. This issue has persisted through multiple tunes and even after replacing the upstream oxygen sensors with new OE NTK units. While Bank 1 STFTs function normally, Bank 2 remains unresponsive, raising concerns about a potential problem with the GPEC2 itself.
Diagnostic Steps and Findings Related to GPEC2
Several diagnostic steps have been taken to identify the root cause of the inactive Bank 2 STFTs:
- Oxygen Sensor Verification: All four oxygen sensors exhibit voltage fluctuations, initially suggesting proper operation. However, Bank 2 sensors eventually showed high, static voltage readings around 5V.
- Sensor Replacement: Replacing the upstream oxygen sensors on both banks with new OE NTK units did not resolve the issue.
- VE Bank 2 Disable Parameter Adjustment: Toggling the “ECM 2102 VE Bank 2 Disable” parameter within the HPT tuning software had no effect on the STFTs.
- Sensor Swapping: Swapping the Bank 1 and Bank 2 upstream sensors did not change the behavior; the issue remained on Bank 2.
- Heater Circuit Check: The oxygen sensor heater circuits on Bank 2 were confirmed to be functioning correctly, with proper voltage and resistance readings.
Current tune file
Further Diagnostic Plans for the GPEC2 Issue
Future diagnostic steps include:
- Direct Voltage Comparison: Directly comparing the voltage readings from the Bank 1 and Bank 2 upstream oxygen sensors at the sensor connector with the corresponding readings at the GPEC2 to identify any discrepancies.
- PCM Reset: Disconnecting the battery and shorting the cables to clear any stored fault codes or learned values in the GPEC2, potentially addressing a software or memory-related issue.
First log last night without changing anything
Conclusion: Seeking Solutions for the GPEC2 STFT Issue
The inactive Bank 2 STFTs on this modified Ram 1500 with a GPEC2 present a complex diagnostic challenge. Despite extensive modifications and tuning adjustments, the root cause remains elusive. Further diagnostics, focusing on the GPEC2’s interaction with the oxygen sensors, are necessary to pinpoint the problem and implement a solution. The possibility of a faulty GPEC2 or underlying wiring issue must be considered. Continued investigation and collaboration with experienced tuners familiar with the GPEC2 platform are crucial for resolving this issue and achieving optimal engine performance.
