B334

Chart:

Schematic:

DESCRIPTION
Code B334 will set if the ignition is on and the Body Control Module (BCM) is not able to exchange data with the Electronic Control Module (ECM). When this is the only communication code stored, the problem must be one of the following:
- An open in CKT 800H
- An open CKT 800E and 800F or 800G
- A faulty ECM or ECM Calpack

During the time the failure is present, a fail soft value equal to 100°C (212°F) 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
The numbers below refer to circled numbers on the diagnostic chart:
1. This step checks for intermittent operating conditions.
2. This step checks to see if the open is in CKT 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 CKT 800H, or the ECM.

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.