Test 12H - Bus Bias Level Or Bus (+/-) Open

NOTE: For connector terminal identification, see CONNECTOR IDENTIFICATION. For wiring diagram, see WIRING DIAGRAMS . Perform TEST VER-1 after each repair.

CAUTION: Always turn ignition switch to OFF position prior to disconnecting or connecting any module connector.

This test covers following BUS BIAS LEVEL OR BUS (+/-) OPEN trouble codes. Ignition off during bus test is the most common cause for these trouble codes.

BUS BIAS LEVEL TOO LOW
BUS BIAS LEVEL TOO HIGH
BUS (+) OPEN
BUS (-) OPEN
BUS (+) & (-) OPEN
1. Turn ignition on, engine off. Disconnect DRB. Using an external voltmeter, check voltage between chassis ground and Data Link Connector (DLC) terminal No. 4 (Violet/Brown wire). If voltage is not 2.3-2.6 volts, go to step 3).
2. If voltage is 2.3-2.6 volts, check voltage between chassis ground and DLC terminal No. 3 (White/Black wire). If voltage is not 2.3-2.6 volts, go to next step. If voltage is 2.3-2.6 volts, replace DRB cable or cartridge as necessary.
3. Turn ignition off, and disconnect Powertrain Control Module (PCM). PCM is located between DLC and battery, on fenderwell. Using an external ohmmeter, check resistance between PCM terminals No. 26 and 46. If resistance is not 100-140 ohms, replace PCM.
4. If resistance is 100-140 ohms, check resistance of Violet/Brown wire between PCM connector terminal No. 26 and DLC terminal No. 4. If resistance is more than 5 ohms, repair open Violet/Brown wire.
5. If resistance is less than 5 ohms, check resistance of White/Black wire between PCM connector terminal No. 46 and DLC terminal No. 3. If resistance is more than 5 ohms, repair open White/Black wire.
6. If resistance is less than 5 ohms, disconnect Transmission Control Module (TCM). TCM is located on left side of engine compartment, near cowl. Check resistance between TCM terminals No. 5 and 44. If resistance is not 100-140 ohms, replace TCM.
7. If resistance is 100-140 ohms, check resistance of White/Black wire between TCM connector terminal No. 4 and DLC terminal No. 3. If resistance is more than 5 ohms, repair open White/Black wire.
8. If resistance is less than 5 ohms, check resistance of Violet/Brown wire between TCM connector terminal No. 43 and DLC terminal No. 4. If resistance is more than 5 ohms, repair open Violet/Brown wire.
9. If resistance is less than 5 ohms, check resistance of Violet/Brown wire between TCM connector terminals No. 5 and No. 43. If resistance is more than 5 ohms, repair open Violet/Brown wire.
10. If resistance is less than 5 ohms, check resistance of White/Black wire between TCM connector terminals No. 4 and terminal No. 44. If resistance is more than 5 ohms, repair open White/Black wire.
11. If resistance is less than 5 ohms, reconnect DRB. Using DRB in voltmeter mode, check voltage on PCM connector terminal No. 11 (Dark Blue wire). If voltage is not more than 10 volts, repair open Dark Blue wire.
12. If voltage is more than 10 volts, turn ignition off. Using DRB in ohmmeter mode, check resistance of PCM connector terminal No. 57 (Black/Red wire). If resistance is more than 5 ohms, repair open Black/Red wire. If resistance is less than 5 ohms, replace TCM.