For 1990-2009 cars

### Circuit Description

The Powertrain Control Module (PCM) is the control center of the fuel injection system. It constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The PCM also performs the diagnostic function of the system. It can recognize operational problems, alert the driver through the Malfunction Indicator Lamp (MIL) (Check Engine), and store a DTC or DTCs which identify the problem areas to aid the technician in making repairs. The PCM consists of 2 internal sides that communicate to each other. When communication between the 2 sides is lost, the PCM cannot function properly and a DTC will set.

### Conditions for Setting the DTC

The PCM cannot communicate between the 2 sides.

### Action Taken When the DTC Sets

• | The malfunction indicator lamp (MIL) will illuminate.

• | The PCM will attempt to record the operating conditions at the time during which you detect this failure, however, since this is a internal PCM failure, you cannot rely on this information. This information will store in the Freeze Frame and Failure Records buffers.

• | A history DTC stores.

### Conditions for Clearing the MIL/DTC

• | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.

• | A history DTC will clear after 40 consecutive warm-up cycles without a fault.

• | The MIL/DTCs can be cleared by using the scan tool.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored on the scan tool for later reference.

2. Replacement PCM's must be reprogrammed. Refer to the latest Techline information for programming procedures.

#### DTC P0600-Loss of Serial Communication Link

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Replace the PCM. Is the action complete? | -- | Go to Step 3 | --
3 |

1. Using the scan tool, clear the DTC's.
2. Start the engine and idle at normal operating temperature.
3. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has ran and passed?

--

Go to Step 4

Go to Step 2

4 | Check if any additional DTC's are set. Are any DTC's displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK