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

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 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 of White/Black wire between chassis ground and DLC terminal No. 3. 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 No. 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 Body Control Module (BCM). BCM is located behind right kick panel. Check resistance between BCM terminals No. 14 and 15. See Figure . If resistance is not 100-140 ohms, replace BCM.
  7. If resistance is 100-140 ohms, check resistance of Violet/Brown wire between BCM Black connector terminal No. 14 and DLC terminal No. 4. If resistance is more than 5 ohms, repair open Violet/Brown wire.
  8. If resistance is less than 5 ohms, check resistance of White/Black wire between BCM Black connector terminal No. 15 and DLC terminal No. 3. If resistance is more than 5 ohms, repair open White/Black wire.
  9. If resistance is less than 5 ohms, check resistance between chassis ground and DLC terminal No. 4 (Violet/Brown wire). If resistance is more than 5 ohms, repair short to ground in Violet/Brown wire.
  10. If resistance is less than 5 ohms, check resistance between chassis ground and DLC terminal No. 3 (White/Black wire). If resistance is more than 5 ohms, repair short to ground in White/Black wire.
  11. If resistance is less than 5 ohms, reconnect DRB. Using in voltmeter mode, check voltage on BCM Black connector terminal No. 16 (Pink wire). If voltage is not more than 10 volts, repair Pink wire as necessary.
  12. If voltage is more than 10 volts, check voltage on BCM Black connector terminal No. 12 (Dark Blue/White wire). If voltage is not more than 10 volts, repair open Dark Blue/White wire.
  13. If voltage is more than 10 volts, turn ignition off. Using DRB in ohmmeter mode, check resistance of BCM Black connector terminal No. 13 (Black/Light Green wire). If resistance is more than 15 ohms, repair open Black/Light Green wire.
  14. If resistance is less than 15 ohms, check resistance of BCM case ground. If resistance is more than 5 ohms, repair BCM case ground as necessary. If resistance is less than 5 ohms, replace BCM.