Encountering a check engine light after a car repair can be frustrating, especially when the vehicle seems to be running smoothly. This is precisely the situation faced by a GM Silverado owner who recently swapped out their transmission and is now grappling with a persistent P2535 error code. Let’s delve into this issue, understand what the P2535 code signifies, and explore potential solutions for this perplexing problem.
The initial query comes from a user who replaced the transmission in their 2009 Silverado with a unit from a 2010 model. While reporting no drivability issues in the six months since the swap, a check engine light remains illuminated, accompanied by the diagnostic trouble code (DTC) P2535. Adding to the confusion, the user mentions that generic code readers might only display a P0700 code, which is a general transmission fault indicator, making the specific P2535 code harder to pinpoint without a more advanced scanner.
The core question revolves around whether the Transmission Control Module (TCM) from the 2010 transmission needs to be reprogrammed or “flashed” to be fully compatible with the 2009 Silverado’s Engine Control Module (ECM). The user contacted a GM dealer who suggested flashing the TCM as a potential fix, but with a significant cost and no guarantee of success. This hesitation is understandable, especially since the transmission appears to be functioning flawlessly. The dealer quoted a price of $150 for a flash that “may work,” and if unsuccessful, an additional $600 for a new TCM plus flashing and labor.
The user’s observation that the 2010 TCM seems to be communicating effectively with the 2009 ECM, given the smooth transmission operation, is a valid point. This raises the question: Is the P2535 code a result of a subtle incompatibility or a completely different issue altogether? While the P0700 code broadly indicates a transmission fault, the P2535 code itself requires further investigation to understand its specific meaning in this context. Unfortunately, the original poster was unable to find specific information on the P2535 code, highlighting the need for more detailed diagnostic resources.
For anyone facing a P2535 code after a transmission replacement, especially in GM vehicles, consider these steps:
- Professional Scan: Obtain a professional-grade scan to confirm the P2535 code and check for any other related codes that might provide further clues.
- TCM Compatibility: Investigate the compatibility of the 2010 TCM with the 2009 Silverado. While physically compatible, software or calibration differences could be triggering the code.
- Consult a Specialist: Seek advice from a transmission specialist or a mechanic experienced with GM vehicles and TCM programming. They can offer more specific guidance than a generic dealer response.
- Consider Flashing: If TCM incompatibility is suspected, explore options for TCM flashing. Independent shops specializing in ECU/TCM programming might offer more cost-effective solutions than dealerships.
In conclusion, while the transmission swap seems mechanically sound, the persistent P2535 code suggests a potential electronic communication issue, likely related to the TCM. Further diagnostics and expert consultation are crucial before committing to costly solutions like TCM flashing or replacement. Understanding the nuances of error codes like P2535 and the complexities of modern vehicle electronics is key to effective auto repair.
