Code B334 - Loss Of ECM Data: Notes

Code B334 will set if the ignition is on and the BCM is not able to exchange data with the ECM (if any other communication codes are stored along with B334, see the end of this article, MULTIPLE INTERMITTENT CODES). When this is the only communication code stored, the problem must be one of the following:

• An open in circuit 800H
• An open circuit 800E and 800F or 800G
• A faulty ECM or ECM CalPak

During the time the failure is present a fail soft value equal to 100°C will be used for the coolant temperature, the cooling fans will be commanded to high speed, and no ECM diagnostic information will be available for display. Also, while in the service diagnostic mode, this code will remain active, always checking for proper operation.

1. This step checks for intermittent operating conditions.
2. This step checks to see if the open is in circuit 800H or the rest of the data circuitry.
3. A double open condition is isolated in this step, which occurs on both sides of the ECM, in the dash side of the data line.
4. This step isolates the fault to be poor terminal contact at the engine to dash harness interconnect circuit 800H, or the ECM.