For 1990-2009 cars
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Data Link Connector (DLC) allows the scan tool to interface with the PCM. The DLC provides the power and ground circuits to enable the scan tool. The Class II serial data circuit to the DLC allows bi-directional communication between the PCM and the scan tool. If communication between the scan tool and the PCM cannot be established, the procedure in the DLC Diagnosis table should be used to diagnose the condition.

### Diagnostic Aids

Check the following items:

• | For the PCM to establish communication with the scan tool, system voltage must be between 9.0 and 16.0V. If system voltage is not within this range, refer to Charging System for diagnosis.

• | Ensure that the correct application (model year, car line, VIN code) has been selected on the scan tool, if communication still cannot be established try the scan tool on another vehicle to ensure that the scan tool, Vehicle Interface Module, or cables are not the cause of the condition.

• | An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for poor connections or a damaged harness. Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

### Test Description

The number below refers to the step number on the Diagnostic Table:

1. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

#### DLC Diagnosis

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain ON Board Diagnostic System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn the ignition ON, and leave the engine OFF.
2. Connect a test lamp between the DLC battery feed and ground circuits.

Is the test lamp ON?

--

Go to Step 4

Go to Step 3

3 | Probe the DLC battery feed circuit with a test lamp to chassis ground. Is the test lamp ON? | -- | Go to Step 9 | Go to Step 10
4 |

1. Turn the ignition ON, and leave the engine OFF.
2. Probe the Class II serial data circuit at the DLC with a DMM to ground.

Does the voltage measure the specified value?

0.0V

Go to Step 5

Go to Step 7

5 |

1. Turn the ignition OFF.
2. Disconnect the PCM.
3. Turn the ignition ON, and leave the engine OFF.
4. Probe the Class II serial data circuit at the DLC with a DMM connected to battery positive voltage.

Does the voltage measure the specified value?

0.0V

Go to Step 6

Go to Step 8

6 |

1. Check the Class II serial data circuit for an open between the DLC and the PCM
2. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 11

7 |

1. Check the Class II serial data circuit for a short to voltage.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 11

8 | Locate and repair short to ground in the Class II serial data circuit. Refer to Wiring Repairs . Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
9 | Locate and repair open in the DLC ground circuit(s). Refer to Wiring Repairs . Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
10 | Locate and repair open or short to ground in the DLC battery feed circuit. Refer to Wiring Repairs . Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
11 | Important: : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --