Refer to Engine Controls Schematics .
Circuit Description
The Class 2 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
Inspect for the following:
| • | 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 Symptoms - 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 try the scan tool on another vehicle to ensure that the scan tool or cables are not the cause of the condition. |
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The number below refers to the step number on the diagnostic table:
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The serial data circuit voltage will constantly vary and should measure between 0.5 and 3.0 volts.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Does the test lamp illuminate while probing both circuits? | -- | ||
3 | Connect a test lamp between the battery feed circuit of the Data Link Connector and a good ground. Does the test lamp illuminate? | -- | ||
Does the voltage measure less than the specified value? | 4.5V | |||
5 |
Does the voltage measure at or near the specified value? | 0.0V | ||
6 | Repair the open in the Class II serial data circuit . Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
7 | Repair the short to voltage in the Class II serial data circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | ||
8 | Repair the short to ground in the Class II serial data circuit. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |
9 | Repair the open in the DLC ground circuits. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |
10 | Repair open or short to ground in the DLC battery feed circuit. Replace the fuse, if necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | -- | |
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- |
