P107

DTC PO47/P107:

UART (Serial Data) Circuit:

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

The data from the PCM to the IPC contains engine operating information. The PCM-IPC data includes engine coolant temperature, rpm and injector pulse width values so the PCM can control cooling fans and the IPC can display rpm and mph. The IPC 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 IPC and Code IO34 will be displayed as current. (Code P047/P107 is current in the PCM but can't be sent to the IPC because of the UART fault.) If the UART fault is corrected, both Code P047/P107 and Code IO34 will be displayed as history codes.

Code P047/P107 should be diagnosed using the chart for Code IO34.

TEST CONDITIONS
1. Code P012 not set.
2. Engine speed 500 rpm or greater for 20 seconds.

FAILURE CONDITION
PCM receives invalid data from IPC for 5 seconds.

ACTION TAKEN
1. PCM turns "ON" the Malfunction Indicator Lamp (MIL) (Service Engine Soon).
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 not functioning at all.
3. Checking if the PROM is correctly seated in socket.
4. Checking for exactly which components have data link problem with the IPC.
5. Checking if the IPC is having a data link problem with the PCM or if just the PCM is having a data link problem with the IPC.
6. Check if the data link is open or if the PCM is faulty.
7. Checking for a wake-up sequence problem.