On-Board Diagnostic (OBD) System Check
NOTE:
DTCs are retrieved using a Tech 1 or 2 scan tool, or other OBD-II compatible scan tool connected to OBD-II 16-pin Data Link Connector (DLC). See Fig 1. DLC is located below instrument panel, on driver's side of vehicle. For DLC terminal identification, see DLC TERMINAL IDENTIFICATION table.
The OBD system check is an organized approach in identifying a problem created by an electronic engine system malfunction. It must be the starting point for any driveability complaint diagnosis, because it directs service technician to the next logical step in diagnosing a complaint. Understanding and using it correctly will reduce diagnostic time and prevent unnecessary replacement of good parts.
- Connect scan tool to DLC. Turn ignition on. If scan tool powers up, go to next step. If scan tool does not power up, see DATA LINK CONNECTOR DIAGNOSIS under CIRCUIT TESTS.
- Attempt communication with PCM. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to step 4.
- Attempt to start engine. If engine starts and continues to run, go to step 6. If engine does not start, go to step 5.
- Attempt to establish communication with other systems connected to same serial data line (Passlock®/EVO, ATC, ABS controllers). If scan tool communicates with other systems, see DATA LINK CONNECTOR DIAGNOSIS under CIRCUIT TESTS. If scan tool does not communicate with other systems, diagnose systems in question. See appropriate article in ACCESSORIES & EQUIPMENT.
- Using scan tool, check for PCM DTCs. If any last test failed, history or MIL request DTCs are set, identify and diagnose DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are set, see NO START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
- If DTC P0215, P1626 or P1631 is set, identify and diagnose DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If listed DTCs are not set, go to next step.
- Turn ignition on. Using scan tool, check ECT sensor value with engine cold. Start engine and allow it to reach normal operating temperature. Recheck ECT sensor value along with other sensor values and compare with specified typical values. See SCAN TOOL DATA . If displayed values are within specified ranges, suspect an intermittent fault. See INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article. If displayed values are not within specified ranges, diagnose suspect component. See appropriate SYSTEM & COMPONENT TESTING article.
DLC TERMINAL IDENTIFICATION
| Terminal No. | Wire Color | Circuit Function |
|---|---|---|
| 1 | N/A | Not Used |
| 2 | Purple | Serial Data Signal (Class II) |
| 3 | N/A | Not Used |
| 4 | Black | Ground |
| 5 | Black/White | PCM Ground |
| 6-7 | N/A | Not Used |
| 8 | Black/White | Keyless Entry Program Enable Signal |
| 9 | Tan | SIR Serial Data |
| 10-11 | N/A | Not Used |
| 12 | Tan/White | ABS Diagnostic Signal (15,000 GVW Only) |
| 13 | Orange | TCM Diagnostic Signal |
| 14 | Dark Green | Entertainment/Comfort Diagnostic Signal |
| 15 | N/A | Not Used |
| 16 | Orange | Fuse Output (B+) |