GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1997 🢒 S/T Isuzu - 2WD 🢒 Restraints 🢒 SIR 🢒 DTC B1042 Loop Energy Reserve Voltage Low

Object Number: 57148 Size: LF

Circuit Description

During the Turn On tests performed at the beginning of each ignition cycle, the supplemental restraint Diagnostic Energy Reserve Module (DERM) delays charging of the Driver 36 VLR terminal A4 power supply. After the delay has expired the Driver 36 VLR power supply is allowed to charge. The DERM monitors the Driver 36 VLR power supply to ensure that it has charged to a voltage above a specified value within 10 seconds after ignition 1 voltage is first applied to the DERM. When the Driver 36 VLR power supply does not reach the specified voltage within the allowed time, or once reaching the specified voltage, falls below it for 500 milliseconds, DTC B1042 is set.

Conditions for Setting the DTC

The voltage measured at the Driver 36 VLR power supply does not exceed a specified value within 10 seconds after ignition 1 voltage is first applied to the DERM, or, once the Driver 36 VLR power supply reaches the specified value, the Driver 36 VLR power supply falls below the specified value for 500 milliseconds during continuous monitoring.

Action Taken When the DTC Sets

The DERM turns on the AIR BAG warning lamp and sets a diagnostic trouble code.

Conditions for Clearing the DTC

The voltage measured at the Driver 36 VLR terminal A4 is above a specified value for 500 milliseconds during continuous monitoring.

Diagnostic Aids

An intermittent condition may be caused by one of the following reasons:

    • A short from the Driver 36 VLR to B+.
    • An open from the Driver 36 VLR to ground.
    • A short inside the supplemental restraint arming sensor.

Test Description

Refer to step numbers on the diagnostic table.

  1. Start at the SRS Diagnostic System Check for all diagnosis.

    2.

  2. This test determines if the diagnostic trouble code has set falsely.

    3.

  3. This test checks whether a malfunctioning supplemental restraint arming sensor is preventing the Driver 36 VLR from charging. This test will cause DTC B1014 (Supplemental Restraint Arming Sensor Disconnected) to set.

    4.

  4. This test determines if a short to B+ is preventing the Driver 36 VLR from charging.

    5.

  5. This test locates a short to B+ which is preventing the Driver 36 VLR from charging.

    6.

  6. This test determines if a short-to-ground is preventing the Driver 36 VLR from charging.

    7.

  7. This test locates the short-to-ground that is preventing the Driver 36 VLR from charging.

When measurements are requested in this table, use J 39200 Digital Multimeter with correct terminal adapter fromJ 35616 Connector Test Adapter Kit. When a check for proper connection is requested, refer to Intermittents and Poor Connections in Section 8A4. When a wire, connector or terminal repair is requested, use J-38125 Terminal Repair Kit and refer to Wiring Repair.

DTC B1042- Loop Energy Reserve Voltage Low

Step

Action

Value

Yes

No

1

Was the SRS Diagnostic System Check performed?

Go to Step 2

Go to SRS Diagnostic System Check

2

  1. Turn ON the ignition switch.
  2. Using the Scan Tool SRS Data List function select Driver 36 VLR.

Is the specified voltage more than the value specified?

32.5 V

Go to Integrity Check

Go to Step 3

3

  1. Record the displayed voltage on the repair order.
  2. Turn OFF the ignition switch.
  3. Disconnect the yellow 2-way electrical connector C214 at the base of the steering column.
  4. Disconnect the supplemental restraint arming sensor.
  5. Turn ON the ignition switch.
  6. Using the Scan Tool SRS Data List Function select Driver 36 VLR.

Is the displayed voltage about the same as the recorded voltage?

Go to Step 5

Go to Step 4

4
  1. Turn OFF the ignition switch.
  2. Replace the supplemental restraint arming sensor. Refer to Supl Rst Arming Sensor .

Has the sensor been replaced?

Go to Step 13

5

Using the Scan Tool SRS Data List Function select Ignition.

Is the displayed voltage about the same as the recorded voltage?

Go to Step 6

Go to Step 9

6

  1. Turn OFF the ignition switch.
  2. Disconnect the supplemental restraint arming sensor jumper harness electrical connector C109.
  3. Turn ON the ignition switch.
  4. Using the Scan Tool SRS Data List Function select Ignition.

Is the displayed voltage about the same as the recorded voltage?

Go to Step 7

Go to Step 8

7
  1. Turn OFF the ignition switch.
  2. Repair the short-to-B+ from circuit 236 of the SRS wiring harness.

Has the short circuit been repaired?

Go to Step 13

8
  1. Turn OFF the ignition switch.
  2. Repair the short-to-B+ from circuit 236 of the supplemental restraint arming sensor jumper harness.

Has the short circuit been repaired?

Go to Step 13

9

Turn OFF the ignition switch.

Is the recorded voltage on the repair order less than the value specified?

1 V

Go to Step 10

Go to Integrity Check

10

  1. Disconnect the supplemental restraint discriminating sensor intermediate harness electrical connector C109.
  2. Turn ON the ignition switch.
  3. Using the Scan Tool SRS Data List Function select Driver 36 VLR.

Does the scan tool display a value less than the value specified?

1 V

Go to Step 11

Go to Step 12

11
  1. Turn OFF the ignition switch.
  2. Repair the short-to-ground from circuit 236 in the SRS wiring harness.

Has the short circuit been repaired?

Go to Step 13

12
  1. Turn OFF the ignition switch.
  2. Repair the short-to-ground from circuit 236 in the supplemental restraint arming sensor jumper harness.

Has the short circuit been repaired?

Go to Step 13

13
  1. Reconnect all the SRS components.
  2. Ensure that the components are properly mounted.

Have all the SRS components been reconnected and mounted?

Go to Step 14

14

Clear the SRS Diagnostic Trouble Codes.

Have the SRS Diagnostic Trouble Codes been cleared?

Go to SRS Diagnostic System Check