GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 Canyon Pickup - 2WD 🢒 DTC 🢒 DTC B1441, B1442, or B1443
Table 1: Correct Ignition Switch Inputs

Circuit Description

The body control module (BCM) monitors the ignition inputs Ignition Off/Run/Crank, Ignition 1 Run/Crank and the Ignition Accessory signals supplied from the ignition switch. The BCM uses the sequence that the signals appear, their voltage levels and the engine run flag (ERF) status to determine the power mode. Battery voltage is supplied to the ignition switch by the IGN TRANSD fuse. The ignition key resistor signal from the BCM provides a 5-volt supply voltage to the ignition switch. The following table shows the correct ignition switch signals.

Correct Ignition Switch Inputs

Ignition Switch Position

BCM Input and Scan Tool Display

Ignition Accessory

Ignition 1 Run/Crank

Ignition Off/Run/Crank

OFF

Inactive

Inactive

Active

ACC

Active

Inactive

Inactive

ON

Active

Active

Active

START

Inactive

Active

Active

DTC Descriptors

This diagnostic procedure supports the following DTCs.

    • DTC B1442 Device Ignition OFF, RUN, and CRANK Circuit Open
    • DTC B1443 Device Ignition OFF, RUN, and CRANK Circuit High

Conditions for Running the DTC

Battery positive voltage is 9-16 volts.

Conditions for Setting the DTC

DTC B1442

The BCM detects that the Off/Run/Crank signal is open for at least 1 second.

DTC B1443

The BCM detects that the Off/Run/Crank signal is shorted to voltage for at least 1 second.

Action Taken When the DTC Sets
    • The BCM stores DTC B1442 or B1443 in memory.
    • The BCM determines a fail-safe power mode dependent on the last valid power mode detected and the state of the ERF.

Conditions for Clearing the DTC
    • A current DTC clears when the malfunction is no longer present.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Test Description

The number below refer to the step number on the diagnostic table.

  1. The correct reading on this step should be B+, but the parameter was scaled to maximum 5 volts, to increase reading accuracy in the lower range.

Step

Action

Values

Yes

No

Schematic Reference: Body Control System Schematics and Power Distribution Schematics

Connector End View Reference: Data Communication Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Important: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.

  1. Install a scan tool.
  2. Observe the Ignition Off/Run/Crank parameter with the scan tool.
  3. Turn the ignition to all positions and compare the parameter to the correct ignition switch inputs table above.

Does the Ignition Off/Run/Crank signal display correctly?

--

Go to Step 3

Go to Step 6

3

  1. Observe the Crank Voltage parameter with the scan tool.
  2. Turn OFF the ignition.

Does the scan tool display the specified value?

5 V

Go to Step 4

Go to Step 6

4
  1. Observe the Crank Voltage parameter with the scan tool.
  2. Turn ON the ignition switch, with the engine OFF.

Is the voltage displayed about this value?

4.4 V

Go to Step 5

Go to Step 6

5

Important: The engine may start during this procedure. Turn the ignition OFF after verifying this power mode.

  1. Observe the Crank Voltage parameter with the scan tool.
  2. Turn the ignition switch to START position.

Is the voltage displayed in this range?

1.7-4.2 V

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 6

6
  1. Place the ignition switch in the OFF position, and pull the key off the ignition switch.
  2. Disconnect the body control module (BCM) harness connector C2.
  3. Probe the Ignition Off/Run/Crank circuit with a test lamp connected to a good ground.
  4. Probe the Ignition Off/Run/Crank circuit with a test lamp connected to B+.

Does the test lamp illuminate for either test?

--

Go to Step 10

Go to Step 7

7
  1. Place the key into the ignition switch without rotating the switch.
  2. Probe the Ignition Off/Run/Crank circuit at the BCM C2 connector with a test lamp connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 11

8
  1. Disconnect the ignition switch harness connector.
  2. Reconnect the BCM harness connector C2.
  3. Measure the voltage between ignition key resistor signal circuit at the ignition switch connector and a ground.

Is the voltage measured about this value?

5 V

Go to Step 12

Go to Step 9

9
  1. Disconnect the BCM harness connector C2.
  2. Test the ignition key resistor signal circuit between the BCM and the ignition switch for a short to ground, a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

10
  1. Disconnect the ignition switch harness connector.
  2. Test the Ignition Off/Run/Crank circuit for a short to ground or short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 12

11
  1. Disconnect the ignition switch harness connector.
  2. Test the Ignition Off/Run/Crank circuit for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs .
  3. Test the battery positive voltage circuit of the ignition switch for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 12

12

Inspect for poor connections at the harness connector of the ignition switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

13

Inspect for poor connections at the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

14

Replace the ignition switch. Refer to Ignition and Start Switch Replacement .

Did you complete the replacement?

--

Go to Step 16

--

15

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 16

--

16
  1. Reconnect all disconnected connectors.
  2. Turn the ignition ON, with the engine OFF.
  3. Clear the DTCs with the scan tool.
  4. Operate the vehicle within the Conditions for Running the DTCs as specified in the supporting text.

Does DTC B1442 or B1443 reset?

--

Go to Step 1

System OK