For 1990-2009 cars
Engine Controls Components
Power, Ground, MIL, and DLC
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

### Circuit Description

The Class 2 serial data circuit to the data link connector (DLC) allows bi-directional communication between the powertrain control module (PCM) and a 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

Inspect the following items:

• | For the PCM to establish communication with the scan tool, system voltage must be between 9.0 and 16.0 volts. If system voltage is not within this range, refer to Diagnostic System Check - Engine Electrical in Engine Electrical.

• | Ensure that the correct application (model year, carline, VIN code) has been selected on the scan tool. If communication still cannot be established, use the scan tool on another vehicle in order to determine if the scan tool or the cables are the cause of the condition.

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

### Test Description

The number below refers to the step number on the diagnostic table:

1. The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be performed.

#### DLC Diagnosis

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Disconnect the scan tool.
2. Turn on the ignition, leaving the engine off.
3. Probe the data link connector (DLC) B+ circuit with a test lamp connected to chassis ground.

Does the test lamp illuminate?

--

Go to Step 3

Go to Step 10

3 | Probe both of the DLC ground circuits with a test lamp to B+. Does the test lamp illuminate at both ground circuits? | -- | Go to Step 4 | Go to Step 9
4 | Probe the Class 2 serial data circuit at the DLC with a DMM connected to ground. Does the voltage approximately equal the specified value? | 0 V | Go to Step 5 | Go to Step 7
5 |

1. Turn off the ignition.
2. Disconnect the PCM.
3. Turn on the ignition, leaving the engine off.
4. Probe the Class 2 serial data circuit at the DLC with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 6

6 |

1. Test the Class 2 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 in Wiring Systems.

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 11

7 |

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

Did you find and correct the condition?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 11

8 | Locate and repair the short to ground in the Class 2 serial data circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
9 | Locate and repair the open in the affected DLC ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
10 | Locate and repair the open or short to ground in the DLC B+ circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --
11 | Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check | --