GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Sierra - 4WD 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC B1480 Battery Rundown Protection Circuit Malf

For a full page schematic, refer to

Cell 51: Inadvertent Power Relay, Courtesy Lamp Relay


Object Number: 294616 Size: FS
Body Control Module Components
Body Control System Circuit Description
Cell 51: Turn Signals, RAP Relay (uplevel only)
Cell 51: Head Lights
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Power Distribution Schematics
Interior Lights Schematics
Interior Lights Schematics
Interior Lights Schematics
Ground Distribution Schematics
Interior Lights Schematics
Ground Distribution Schematics
 .

Circuit Description

The battery rundown protection function allows the body control module (BCM) to disable the courtesy lamps, the cargo lamps and the underhood lamp 40 minutes after the ignition switch is turned OFF. The BCM monitors the output of the inadvertent power relay on CKT 1732.

Conditions for Setting the DTC
    •  When the BCM commands the inadvertent power relay on via CKT 1393 and CKT 1732 has an absence of voltage to the BCM, DTC B1480 will set.
    • The system voltage must be between 9.0-16.0 volts.
    • The above conditions must be met for 0.5 seconds.

Action Taken When the DTC Sets

The following lamps will be disabled:

    • The dome
    • The glove box
    • The reading
    • The underhood

Conditions for Clearing the MIL/DTC
    • This DTC will clear after the condition for setting the fault is corrected.
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.
    • Use a scan tool in order to clear the history DTC(s).

Diagnostic Aids

Important: Use the appropriate probe from the connector test adapter kitJ 35616 for any probing of the bussed electrical centers (BECs) in this table in order to avoid damage to the BECs.

    • Always diagnose the first DTC listed on the scan tool.
    • The scan tool must display DTC B1480 as a current code before performing diagnostics.
    • Perform a visual inspection for loose or poor connections at all related components.
    • Check for an open in CKT 40 or an open CTSY LP fuse.
    • Refer to Testing for Electrical Intermittents in Wiring Systems.

Test Description

Step number(s) below refer to the same step number(s) in the Diagnostic Table

  1. This step tests the CTSY LP fuse.

    2.

  2. This step inspects the control circuit of the inadvertent power relay, inadvertent power relay and the CTSY LP fuse.

    3.

  3. This step determines if CKT 1732 is open or the BCM is unable to monitor voltage on circuit 1732.

    4.

  4. This step determines if CKT 40 is open.

    5.

  5. This step checks if CKT 1393 is open between the inadvertent power relay and the BCM.

    6.

  6. This step determines if CKT 1732 is open between the mid bussed electrical center (MBEC) and the BCM.

Step

Action

Value(s)

Yes

No

1

Was the BCM Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Body Control System

2

Turn dome light switch ON (defeat switch OFF).

Test both sides of the CTSY fuse with a test lamp to ground.

Does the test lamp light on both sides of the fuse?

--

Go to Step 6

Go to Step 3

3

Does the test lamp light on either side of the fuse?

--

Go to Step 4

Go to Step 5

4

Locate and repair the short to ground in CKT 40 (ORN) or CKT 1732 (ORN).

Is the repair complete?

--

Go to Step 16

--

5

Replace the underhood bussed electrical center (UBEC).

Is the repair complete?

--

Go to Step 16

--

6
  1. Turn the ignition switch to the RUN position.
  2. With the a scan tool, monitor the current DTCs.
  3. Using a fused jumper, backprobe CKT 1393 (DK BLU) cavity A8 of the brown BCM connector to ground.

Does the scan tool display DTC 1480 as current?

--

Go to Step 7

Go to Step 15

7
  1. Disconnect the blue BCM (C2) connector.
  2. Remove the comb from the connector.
  3. Ensure that the fused jumper still connected. Backprobe, in order to prevent damage to terminal, with a J 39200 digital multimeter (DMM).
  4. Measure the voltage between CKT 1732 (ORN) wire cavity B12 and ground.

Does the J 39200 DMM display battery voltage?

--

Go to Step 15

Go to Step 8

8
  1. Remove the fused jumper wire.
  2. Remove inadvertent power relay from mid bussed electrical center (MBEC).
  3. Use the appropriate probe from the J 35616 connector test adapter kit for the next step.
  4. With a J 39200 DMM, measure the voltage between the inadvertent power relay cavities 1 and 5 (top 2 cavities of the relay connector) to ground.

Does the J 39200 DMM display battery voltage at both cavities?

--

Go to Step 9

Go to Step 13

9
  1. Disconnect the BCM C1 (brown) connector.
  2. Remove the comb from the connector.
  3. Use the appropriate probe from the J 35616 connector test adapter kit for the next step.
  4. With a J 39200 DMM, measure the resistance between the inadvertent power relay CKT 1393 cavity 2 (lower left cavity of the relay connector) and the BCM cavity A8 brown BCM (C1) connector.

Is the resistance within the specified range?

0-5 ohms

Go to Step 10

Go to Step 11

10
  1. Use the appropriate probe from the J 35616 connector test adapter kit for the next step.
  2. With a J 39200 DMM, measure the resistance on CKT 1732 between the BCM at terminal B12 of the light blue (C2) connector and terminal A10 of the MBEC (C1) connector.

Is the resistance within the specified range?

0-5ohms

Go to Step 14

Go to Step 12

11

Locate and repair open in CKT 1393 (DK BLU) between the BCM and the inadvertent power relay (MBEC).

Is the repair complete?

--

Go to Step 16

--

12

Locate and repair open in CKT 1732 (ORN) between the BCM and the inadvertent power relay (MBEC).

Is the repair complete?

--

Go to Step 16

--

13

Locate and repair open in CKT 40 (ORN) between inadvertent power relay and the UBEC.

Is the repair complete?

--

Go to Step 16

--

14

Replace the inadvertent power relay.

Is the repair complete?

--

Go to Step 16

--

15
  1. Replace the BCM. Refer to Body Control Module Replacement .
  2. Program the BCM with the proper calibrations. Refer to Body Control Module (BCM) Programming/RPO Configuration .
  3. Perform the learn procedure.

Is the repair complete?

--

System OK

--

16

Clear the DTCs. Refer to Clearing DTCs .

Is the repair complete?

--

System OK

--