GM diagnostic strategy does not support the practice of swapping control modules during the course of diagnosis or to expedite a repair. Features in today’s vehicles are increasingly software configurable.
They can affect vehicle safety systems, anti-theft systems, performance components and customer personalization information.
First introduced in 2010, GM’s Global Architecture (Global A) electrical system and the later Vehicle Intelligence Platform (VIP) electrical system do not allow control modules to be swapped between vehicles.
Problems can occur on these models when attempting to swap a control module configured for one vehicle into another. Symptoms such as no-start conditions and DTCs that cannot be cleared are to be expected. Issues also may be introduced into vehicles that exhibit no symptoms until a later date, adding to the complexity of diagnosing the vehicle.
These “sleeper issues” may be triggered only after multiple key cycles or only after battery power has been removed from the BCM. Such issues can be time-consuming to rectify, driving up unnecessary warranty expenses and leading to customer dissatisfaction.
Symptoms of Module Swapping
A variety of symptoms may appear in a vehicle containing one or more control modules swapped from a like vehicle. Depending upon which control modules have been swapped, possible symptoms include:
• The VIN read by GDS and SPS does not match the vehicle.
• Current DTC B3902 – Incorrect IMMO ID Rec. set in IPC, SDM, ECM, HVAC, Steering Column Lock Control Module (if equipped) or BCM. There are no warning lamps or DIC messages and this DTC cannot be cleared.
• IPC module displays (- – -) for odometer and trip odometer values.
• Vehicle will enter power mode only if the key fobs that match the donor vehicle BCM are included in the swap.
• BCM and/or ECM has current DTC B389A – Environment Identification. There is a Service Theft System message on the DIC, the Security MIL is illuminated, and this DTC cannot be cleared.
• ECM odometer value is incorrect for the vehicle.
• Radio displays Locked.
Security Protocol
Swapping control modules, including the ECM, BCM, EBCM, SDM, TCM, ECC (HVAC), EPS, HPCM, IPC, and Radio, between vehicles with Global Architecture electrical systems will damage both controllers and result in a no start condition on both vehicles due to the vehicle’s security code protocol.
These modules all have IDs that must match in order for the BCM to allow the engine to start.
The control modules are coded to the vehicle when they are first programmed, which results in a unique ID being permanently stored in that module.
Swapping these security-related modules will cause difficult and time-consuming remediation processes that may include the purchase of new components for both vehicles.
There are a number of security methods in operation, including:
Security Code – The purpose of the security code is to protect the vehicle’s security information against tampering.
It’s a random code, unique to each vehicle, generated at the vehicle assembly plant.
Environmental ID – The purpose of the Environmental ID is to increase the time and complexity involved in attempting a vehicle theft by swapping control modules. In a potential theft situation, it will not allow continued running of the engine
.
Seed and Key – The purpose of Seed and Key is to protect certain control modules from unauthorized reprogramming when they are outside the assembly plant environment. Each control module that implements Seed and Key is manufactured with a unique seed value and a corresponding key value stored in memory.
On today’s vehicles, the electrical architecture plays a significant role in how a vehicle is equipped and operates.
The best diagnostic path for all vehicles, regardless of equipment, is to follow the procedures outlined in the appropriate Service Information.
Check out Bulletin #25-NA-256 for more details.
