Test C: Scan Tool Does Not Communicate With Electronic Brake Control Module

NOTE: Brake Pressure Modulator Valve (BPMV) and Electronic Brake Control Module (EBCM) are not serviced separately.

1. If engine controls diagnostic system check has been performed, go to next step. If engine controls diagnostic system check has not been performed, perform engine controls diagnostic system check. See ENGINE CONTROLS DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
2. Connect scan tool to Data Link Connector (DLC). DLC is located under left side of instrument panel, right of steering column. Attempt to communicate with Brake Pressure Modulator Valve/Electronic Brake Control Module (BPMV/EBCM). If communication is not established, go to next step. If communication is established, system is okay.
3. If vehicle is equipped with Anti-Lock Brake System (ABS), go to next step. If vehicle is not equipped with ABS, go to step  5 .
4. Attempt to communicate with PCM. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to step  6 .
5. Turn ignition switch to LOCK position. Disconnect BPMV/EBCM 24-pin harness connector. BPMV/EBCM is located under brake master cylinder. Measure resistance in White wire between BPMV/EBCM harness connector terminal No. 4 and DLC terminal No. 7. See Figure and Fig 1 . If resistance is 2 ohms or more, repair open in White wire between BPMV/EBCM and DLC. After repair, go to step  2 . If resistance is less than 2 ohms, go to step  12 .
6. Turn ignition switch to LOCK position. Disconnect scan tool from DLC. Turn ignition switch to RUN position. Measure voltage between ground and DLC terminal No. 7 (White wire). If battery voltage exists, go to next step. If battery voltage does not exist, go to step  8 .
7. Using a test light connected to ground, probe DLC terminal No. 7 (White wire). If test light illuminates, go to step  10 . If test light does not illuminate, go to step  11 .
8. Turn ignition switch to LOCK position. Disconnect BPMV/EBCM 24-pin harness connector. BPMV/EBCM is located under brake master cylinder. Measure resistance in White wire between BPMV/EBCM harness connector terminal No. 4 and DLC terminal No. 7. See Figure and Fig 1 . If resistance is less than 2 ohms, go to next step. If resistance is 2 ohms or more, repair open in White wire between BPMV/EBCM and DLC. After repair, go to step  2 .
NOTE: Serial data circuit is connected to DLC, EBCM, PCM and SDM. It may be necessary to disconnect each module to ensure module is not internally grounded. For circuit identification, see DATA LINK COMMUNICATIONS article in WIRING DIAGRAMS.
9. Repair short to ground in serial data circuit. After repair, go to step  2 .
NOTE: Serial data circuit is connected to DLC, EBCM, PCM and SDM. It may be necessary to disconnect each module to ensure module is not internally shorted to voltage. For circuit identification, see DATA LINK COMMUNICATIONS article in WIRING DIAGRAMS.
10. Repair short to voltage in serial data circuit. After repair, go to step  2 .
11. Replace defective scan tool. After repair, go to step  2 .
12. Inspect BPMV/EBCM harness connector for loose, corroded terminals or intermittent condition. See PROBLEM DIAGNOSIS  under INTERMITTENTS. If concern still exists, go to next step. If concern does not exist, go to step  2 .
13. Replace BPMV/EBCM. After repair, go to step  2 .

Fig 1: Identifying Brake Pressure Modulator Valve/Electronic Brake Control Module Harness Connector Terminals