B1970

DTC B1970 Exterior Lamp Power:

CIRCUIT DESCRIPTION
The Body Control Module (BCM) controls all exterior lamps by supplying power from terminal B10 to the high side of the park lamp and the low beam relay coils. The BCM commands the exterior lamps On by grounding the appropriate relay at either terminal C9 or terminal C12.

CONDITIONS FOR SETTING THE DTC
^ The BCM can only test for this condition when the exterior lamp power is active ( headlamp On request ). During this time battery voltage is present at terminal B10.
^ The BCM detects the voltage output at terminal B10 went low ( short to ground ).
^ The condition must be present for 300 ms.

ACTION TAKEN WHEN THE DTC SETS
^ The BCM attempts to reactivate the exterior lamp power every 1.2 seconds until the request is no longer required.
^ Stores a DTC B1970 in the BCM memory

CONDITIONS FOR CLEARING THE DTC
^ The conditions for the fault are no longer present.
^ The use of a scan tool.
^ A history DTC will clear after 50 consecutive ignition cycles if the condition for the fault is no longer present.

DIAGNOSTIC AIDS
^ When the diagnostics direct you to take electrical measurements at the relay box, refer to Fuse Block Details for an end view and terminal assignments of the relay box.
^ The problem may be intermittent if the DTC is a history DTC. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to appear. Refer to Intermittents and Poor Connections. Intermittents and Poor Connections

TEST DESCRIPTION
The following numbers refer to the numbers on the diagnostic table:
2. The status should match the commanded state when the exterior lamp power is commanded On/Off. In most cases a no change in status indicates a circuit problem. A voltage check is made at the furthest point of the circuit to determine it the circuit is complete.
3. This test checks for proper voltage and ground input to the BCM. After checking the voltage and the ground inputs, check the BCM again to see if the DTC resets indicating an internal failure.
6. The problem may be intermittent. Perform a wiggle test to see if the fault reappears.