B334

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 Multiple Intermittent Codes). When this is the only communication code stored, the problem must be one of the following:
^ An open CKT 800E and 800F or 800E and 800D.
^ An open or short to ground in circuit 439 or 1605.
^ 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.

TEST DESCRIPTION
Numbers below refer to numbers on the diagnosis chart.
1. This step checks for intermittent operating conditions.
2. This step checks to see if the open is in CKT 8OOF or 800D.
3. If there is an open in circuit 800F or 800D, this step finds which side of the ALDL it is on.
4. This step checks for an open in circuit 800E.

NOTE ON INTERMITTENTS
If only Code B334 is stored as "History", check the power and grounds for intermittent faults and 800E for an intermittent open circuit. If ECM code EO52 history is also set, refer to ECM Diagnostic Charts. Testing and Inspection