Vehicle On-Board Diagnostic System Check
NOTE:
Use this check as the starting point when diagnosing powertrain, chassis or any other electrical sub-system. BCM is a very reliable component, and is not likely the cause of malfunction. Most malfunctions are caused by faulty wiring, connectors or components.
It is important to establish serial data communications with each module, read DTCs from each module, and record information gathered. The BCM is closest to Data Link Connector (DLC) and is referred to as the data link master. BCM is capable of detecting when another module on class-2 serial data link or CAN link is missing. When BCM detects a module missing, a "U" type DTC will be stored in BCM. If communications cannot be established with BCM, attempting to establish communication with the Sensing and Diagnostic Module (SDM) should be next. The following procedure will aid in diagnosing whether a serial data link fault exists or if an individual module is not capable of communicating:
- Connect scan tool to DLC. See COMPONENT LOCATIONS . Turn ignition on. If scan tool powers up, go to next step. If scan tool does not power up, go to TEST A: SCAN TOOL DOES NOT POWER UP under SYSTEM TESTS.
- Using scan tool, attempt to establish communication with Body Control Module (BCM), Sensing and Diagnostic Module (SDM), PCM (4-cylinder), ECM (V6), Transaxle Control Module (TCM) and EBTCM (if equipped). If scan tool communicates with BCM, go to step 4. If scan tool does not communicate with BCM, go to next step.
- If scan tool communicates with SDM, go to step 8. If scan tool does not communicate with SDM, go to TEST B: NO COMMUNICATION ON CLASS-2 SERIAL DATA LINK under SYSTEM TESTS.
- If no BCM DTCs exist, go to step 8. If "U" type BCM DTCs exist, go to next step. If BCM DTCs other than "U" type exist, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
- If BCM DTC U1300 or U1301 exist, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . On models equipped with V6, if other "U" type BCM DTCs exist, go to next step. On models equipped with 4-cylinder, if other "U" type BCM DTCs exist, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
- If both BCM DTC U2105 and U2106 exist, go to next step. If only BCM DTC U2105 or U2106 exist, perform DTC U2105: LOST COMMUNICATION WITH ECM or DTC U2106: LOST COMMUNICATION WITH TCM diagnosis. If other "U" type DTC exists, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
- If BCM DTC U2100 exists, perform DTC U2100: CAN BUS COMMUNICATIONS MALFUNCTION diagnosis. If BCM DTC U2100 does not exist, perform DTC U2105: LOST COMMUNICATION WITH ECM diagnosis.
- If no SDM DTCs exist, go to next step. If SDM DTC U1064 exists, perform DTC U1064: LOST COMMUNICATIONS WITH BCM . If SDM DTC U1064 does not exist, perform appropriate diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .
- On models equipped with 4-cylinder, go to step 12. On models equipped with V6, if scan tool is able to communicate with ECM, go to next step. On models equipped with V6, if scan tool is not able to communicate with ECM, go to step 11.
- Using scan tool, attempt to establish communication with TCM. If scan tool is able to communicate with TCM, go to step 12. If scan tool is not able to communicate with TCM, check for open in Keyword Protocol 2000 (KWP2000) data link between TCM and DLC. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair as necessary and retest operation. If KWP2000 data link checks okay, replace TCM. See TRANSAXLE CONTROL MODULE under REMOVAL & INSTALLATION.
- Using scan tool, attempt to establish communication with TCM. If scan tool does not communicate with TCM, go to step 16. If scan tool communicates with TCM, check for open in Keyword Protocol 2000 (KWP2000) data link between ECM and DLC. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair as necessary and retest operation. If KWP2000 data link checks okay, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
- On models equipped with 4-cylinder, check for DTCs set in PCM memory. On models equipped with V6, check for DTCs set in ECM or TCM memory. On all models, if DTCs exist, perform appropriate test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If ECM or TCM DTCs exist, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE, or ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS for related diagnostic procedure. If no DTCs exist, go to next step.
- Using scan tool, attempt to communicate with EBTCM. If scan tool communicates with EBTCM, go to next step. If scan tool does not communicate with EBTCM, perform TEST C: NO COMMUNICATIONS WITH ELECTRONIC BRAKE/TRACTION CONTROLS SYSTEM diagnosis.
- Using scan tool, check for DTCs set in EBTCM memory. If DTCs are stored in EBTCM memory, see appropriate ANTI-LOCK article in BRAKES. If no DTCs are stored in memory of EBTCM, go to next step.
- If engine does not start and run, see appropriate BASIC DIAGNOSTIC PROCEDURES article in ENGINE PERFORMANCE. If engine starts and runs, ON-BOARD DIAGNOSTIC SYSTEM CHECK is complete.
- Turn ignition off. Disconnect ECM 64-pin connector J2. Turn ignition on. Using scan tool, attempt to communicate with TCM. If scan tool still does not communicate with TCM, go to next step. If scan tool communicates with TCM, replace ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE.
- Turn ignition off. Disconnect TCM connector. Check for open, short to ground or short to voltage in KWP2000 data link between ECM, TCM and DLC. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. Repair as necessary. Reconnect all disconnected components and connectors. Retest operation. If KWP2000 data link is not open, shorted to ground or shorted to voltage, go to next step.
- Reconnect all disconnected components and connectors ensuring all have a good connection. Retest operation. If problem still persists, replace TCM.