GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC Sierra Denali 🢒 Restraints 🢒 SIR 🢒 DTC B1422
Table 1: Valid States
Table 2: Invalid States

Circuit Description

The hybrid control module (HCM) monitors Ignition 1, Ignition 0 discrete wires from the ignition switch contacts, and the Crank state message from the powertrain control module (PCM). If HCM detects a mismatch between the ignition switch signals and the Crank state message, it will set the DTC. The following table represents correct HCM power mode data:

Valid States

Ignition Switch Position

HCM and BCM inputs and Scan Tool Display

Ignition 0

Ignition 1

Crank State

OFF

Off

Off

False

UNLOCK

On

Off

False

ACC

On

Off

False

ON

On

On

False

START

On

On

True

Conditions for Running the DTC

Either one of the below conditions has to satisfied:

    • Ignition 0 voltage is between 8-16 volts.
    • Power maintain is true and DC/DC direction is 42-14 volts.

Conditions for Setting the DTC

The DTC will set if any of the following cases is detected for about 2.5 milliseconds:

Invalid States

Ignition 0

Ignition 1

Crank State

Off

Off

True

Off

On

False

Off

On

True

On

Off

True

Action Taken When the DTC Sets

The HCM implements default actions when a fault is detected.

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.

Step

Action

Yes

No

Schematic Reference: Starting and Charging Schematics in Engine Electrical

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Retrieve DTCs from body control module (BCM).

Did you record DTC B1440?

Go to DTC B1440

Go to Step 3

3
  1. Install a scan tool.
  2. Turn OFF the ignition.
  3. With a scan tool, monitor the following in HCM and BCM, Data Display:
    4. • Ignition 0
    • Ignition 1

Does the scan tool indicate that all inputs are Off?

Go to Step 4

Go to Step 6

4
  1. Install a scan tool.
  2. Turn the ignition switch to ACC.
  3. With a scan tool, monitor the following in HCM and BCM, Data Display:
    4. • Ignition 0
    • Ignition 1

Does the scan tool indicate that the Ignition 0 input is On?

Go to Step 5

Go to Step 8

5
  1. Turn the ignition switch ON, with the engine OFF.
  2. With a scan tool, monitor the following in HCM and BCM, Data Display:
    3. • Ignition 0
    • Ignition 1

Does the scan tool indicate that the both inputs are On?

Go to Step 10

Go to Step 8

6
  1. Disconnect the ignition switch harness connectors.
  2. With a scan tool, monitor the following in HCM and BCM, Data Display:
    3. • Ignition 0
    • Ignition 1

Does the scan tool indicate that any of the Ignition 0 or Ignition 1 inputs is On?

Go to Step 7

Go to Step 9

7
  1. Disconnect the hybrid control module (HCM) harness connectors.
  2. Test the suspect ignition switch input circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 11

8
  1. Disconnect the ignition switch connectors.
  2. Install a 3-amp fused jumper between the suspect circuits and an ignition switch B+ supply.
  3. With a scan tool, monitor the suspect circuits in HCM and BCM, Data Display:
    4. • Ignition 0
    • Ignition 1

Does the scan tool indicate that the suspect circuit is now On?

Go to Step 9

Go to Step 10

9

Inspect for poor connections at the ignition switch harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 12

10

Important: If this step is performed following step 5, consider ignition 0 circuit of the HCM as suspected circuit.

  1. Disconnect the HCM harness connectors.
  2. Test the suspect ignition switch input circuits for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 11

11

Inspect for poor connections at the HCM harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 13

12

Replace the ignition switch. Refer to Ignition and Start Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 14

--

13

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

Did you complete the replacement?

Go to Step 14

--

14
  1. Reconnect all components.
  2. Use the scan tool in order to clear DTCs.
  3. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

Go to Step 1

System OK