DTC B1440. GMC Truck Savana

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2007 🢒 Savana - AWD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC B1440

Table 1:	Correct Ignition Switch Inputs
Table 2:	Incorrect Ignition Switch Inputs

Circuit Description

The body control module (BCM) is the power mode master responsible for sending ignition switch position information on the class 2 serial data link. The BCM monitors 3 discrete wires from the ignition switch contacts and the engine run flag (ERF) in order to determine the present power mode. The BCM communicates this power mode information to all class 2 modules on the class 2 serial data link. The following table represents correct BCM power mode data:

Correct Ignition Switch Inputs

Ignition Switch Position	BCM Input and Scan Tool Display
Ignition Switch Position	Accessory Switch	Run/Crank	Ignition Unlock
OFF	Inactive	Inactive	Inactive
UNLOCK	Inactive	Inactive	Active
ACC	Active	Inactive	Active
ON	Active	Active	Active
START	Inactive	Active	Active

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1440 Power Mode Master Input Circuits Mismatch

Conditions for Running the DTC

The only requirements are voltage and ground.

Conditions for Setting the DTC

One of the 3 monitored ignition switch circuits has malfunctioned. The DTC will set, if one of the following situations is present:

Incorrect Ignition Switch Inputs

BCM Input and Scan Tool Display			Engine Running
Accessory Switch	Run/Crank	Ignition Unlock	Engine Running
Inactive	Active	Inactive	No
Active	Inactive	Inactive	No
Active	Active	Inactive	No
Inactive	Active	Inactive	Yes
Inactive¹	Active	Active	Yes
Active	Inactive	Inactive	Yes
Active	Inactive	Active	Yes
Active	Active	Inactive	Yes
¹ The module sets the DTC 1 minute after it detects the condition.

Action Taken When the DTC Sets

The BCM implements default actions for each ignition switch position when faults are 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

Schematic Reference: Body Control System Schematics and Power Moding Schematics

Connector End View Reference: Power and Grounding Connector End Views and Data Communication Connector End Views

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

Install a scan tool.
Turn OFF the ignition.
With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:

•	Ignition Unlock

•

Run/Crank

•	Accessory Switch

Does the scan tool indicate that all inputs are inactive?

Go to Step 3

Go to Step 6

Install a scan tool.
Turn the ignition switch to ACC.
With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:

•	Ignition Unlock

•

Run/Crank

•	Accessory Switch

Does the scan tool indicate that the Ignition Unlock and Accessory Switch inputs are active?

Go to Step 4

Go to Step 8

Turn the ignition switch ON, with the engine OFF.
With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:

•	Ignition Unlock

•

Run/Crank

•	Accessory Switch

Does the scan tool indicate that the all inputs are active?

Go to Step 5

Go to Step 8

Important: The engine may start in this step. Turn the engine OFF immediately after reviewing the input data.

Turn the ignition switch to START.
With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:

•	Ignition Unlock

•

Run/Crank

•	Accessory Switch

Does the scan tool indicate that the Ignition Unlock and Run/Crank inputs are Active and the Accessory Switch input is inactive?

Go to Step 11

Go to Step 8

Disconnect the ignition switch harness connectors.
With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:

•	Ignition Unlock

•

Run/Crank

•	Accessory Switch

Does the scan tool indicate that any of the Ignition Unlock, Run/Crank or Accessory Switch inputs is active?

Go to Step 7

Go to Step 9

Disconnect the body control module (BCM) harness connectors.
Test the suspect ignition switch input circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 14

Go to Step 11

Disconnect the ignition switch connectors.
Install a 3-amp fused jumper between the suspect circuits and an ignition switch B+ supply.
With a scan tool, monitor the suspect circuits in Body Control Module, Data Display, Inputs:

•	Ignition Unlock

•

Run/Crank

•	Accessory Switch

Does the scan tool indicate that the suspect circuits are now active/On?

Go to Step 9

Go to Step 10

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

Did you find and correct the condition?

Go to Step 14

Go to Step 12

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

Did you find and correct the condition?

Go to Step 14

Go to Step 11

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

Did you find and correct the condition?

Go to Step 14

Go to Step 13

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

Did you complete the replacement?

Go to Step 14

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

Did you complete the replacement?

Go to Step 14

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

Does the DTC reset?

Go to Step 2

System OK