P047

DTC P047/P107:

Serial Data (CKT 800) Line:

CIRCUIT DESCRIPTION:
The PCM and BCM share information through the UART (Universal Asynchronous Receiver/Transmitter) data link. The BCM is the "Master" of the link and data is only transmitted at the BCM's request. Data is sent in eight-character "Words" at the rate of 8192 characters per second.

The data from the PCM to the BCM contains engine operating information. The PCM-BCM data includes engine coolant temperature, rpm and injector pulse width values so the PCM can control cooling fans and the BCM can display rpm and mph at the IPC. The BCM sends the PCM air conditioning status to be used for idle speed control and ambient (outside) temperature for use in Torque Converter Clutch (TCC) apply and release decisions.

Code P047/P107 is logged in the PCM in the event of a UART fault. If the fault is a current failure, the PCM will not be able to communicate with the BCM and Code 13334 will be displayed as current. (Code P047/P107 is current in the PCM but can't be sent to the BCM because of the UART fault.) If the UART fault is corrected, both Code P047/P107 and Code B334 will be displayed as history codes.

Code P047/P107 should be diagnosed using the chart for BCM Code B334.

TEST CONDITION(S):
1. Code P012 not set.
2. Engine speed 500 rpm or greater for 20 seconds.

FAILURE CONDITION(S):
PCM receives invalid data from BCM for 5 seconds.

ACTION TAKEN:
1. PCM turns "ON" the "SERVICE ENGINE SOON" MIL.
2. PCM sets all incoming data to zero.
3. PCM boosts idle to compensate for possible A/C clutch engagement.
4. Cooling fan control will be based on engine coolant temperature only.

NOTES ON FAULT TREE:
1. If one code is set without the other, the PCM has an internal communication fault.
2. Checking if data link is totally not functioning.
3. Checking if the PROM is correctly seated in socket.
4. Checking for exactly which components have data link problem to the BCM.
5. Checking if the BCM is having a data link problem with the PCM or if just the PCM is having a data link problem with the BCM.
6. Check if the data link is open or if the PCM is faulty.
7. Checking for a wake-up sequence problem.