Code B334, Loss Of ECM Serial Data (TORONADO): Notes

Fig 1: Code B334 Flowchart, Loss of ECM Serial Data (Toronado)

Fig 2: Code B334, Loss of ECM Serial Data (Toronado)

Fig 3: Code B334 Schematic, Loss of ECM Serial Data (Toronado)

Code B334 will set if communication between the ECM and the BCM is lost. If the BCM remains powered and only serial communication is lost, the vehicle will still run; but, with the ignition key on (engine not running), a "Low Oil Pressure" message will be displayed followed by an "Electrical Problem" message about 25 seconds later.

1. If the ECM loses power or ground, the code will set because the ECM cannot communicate; but the key here is that the engine will not start.
2. Checks for serial data at the ECM. Normally voltage should be above 1 volt and varying. The normal 1-5 volts varying only indicates there are no opens up to the ECM.
3. If the code resets and since the prior checks eliminated an open circuit, the fault is poor terminal contact at ECM A8, or a faulty ECM.