For 1990-2009 cars

Refer to

#### Power, Ground, MIL, DLC

Underhood Accessory Wiring Junction Block, Relay Center, PWR WDO and PWR OTR Vent Fuses
IGN, SIR, T/S/G, Cruise, and PCM/Pass Key 1 Cluster Fuses
Cell 14: G100, G111 and G113
IGN, SIR, T/S/G, Cruise, and PCM/Pass Key 1 Cluster Fuses
IGN, SIR, T/S/G, Cruise, and PCM/Pass Key 1 Cluster Fuses
IGN, SIR, T/S/G, Cruise, and PCM/Pass Key 1 Cluster Fuses
Hardwire Indicators
Ignition Switch IGN Main Relay, IGN Main 1, PCM/ABS, CONVENT SOL, DRL, and PCM/Crank Fuses
Handling ESD Sensitive Parts Notice
Ignition Switch IGN Main Relay, IGN Main 1, PCM/ABS, CONVENT SOL, DRL, and PCM/Crank Fuses
Handling ESD Sensitive Parts Notice
DLC Schematic
Engine Controls Components
Powertrain Control Module Description
Ignition System, Knock Sensor
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
, and

#### DLC Schematic

Data Link Communications Components
Data Link Communications Circuit Description
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
SIR Handling Caution
Cluster BATT, RR PWR SCKT, PWR Lock, Rap Relay, CTSY Lamp, FRT PWR SCKT, Cigar/DLC and PWR Mirror Fuses
Cluster BATT, RR PWR SCKT, PWR Lock, Rap Relay, CTSY Lamp, FRT PWR SCKT, Cigar/DLC and PWR Mirror Fuses
Cell 14: G200
Cell 14: G200
in Data Link Communications.

### Circuit Description

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

• | When the Class II serial data circuit is shorted to ground, U1300 or U1305 will be set. Refer to DTC U1300 Class 2 Data Link Low , or DTC U1305 Class 2 Data Link Low or High .

• | When the Class II serial data circuit is shorted to battery positive voltage U1301, or U1305 will be set. Refer to DTC U1301 Class 2 Data Link High , or DTC U1305 Class 2 Data Link Low or High .

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.

Step | Action | Values | 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. Turn On the ignition, with the engine OFF.
2. Attempt to communicate with the PCM

Does the scan tool communicate with the PCM?

--

Go to Diagnostic Aids

Go to Scan Tool Does Not Communicate with Class 2 Device