B1440 heres GMs flow chart. Looks like you might need a scan tool to diag. I would clear it all and see what comes back. Odd you don't get a ABS light with the C0040 unless it messes up and goes away before it comes on.
Circuit DescriptionThe body control module (BCM) is the power mode master responsible for sending ignition switch position information on the class 2 serial data link (SDL). 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 SDL. The following table represents correct BCM power mode data:
Correct Ignition Switch InputsIgnition Switch Position
Ignition Accessory
Ignition 1
Ignition 0
OFF
Inactive
Off
Off
UNLOCK
Inactive
Off
On
ACC
Active
Off
On
ON
Active
On
On
START
Inactive
On
On
DTC DescriptorThis diagnostic procedure supports the following DTC:
DTC B1440 Power Mode Master Input Circuits Mismatch
Conditions for Running the DTCThe only requirements are voltage and ground.
Conditions for Setting the DTCOne of the 3 monitored ignition switch circuits has malfunctioned. The DTC will set, if one of the following situations is present:
Incorrect Ignition Switch InputsIgnition Accessory
Ignition 1
Ignition 0
Engine Running
Inactive
On
Off
No
Active
Off
Off
No
Active
On
Off
No
Inactive
On
Off
Yes
Inactive¹
On
On
Yes
Active
Off
Off
Yes
Active
Off
On
Yes
Active
On
Off
Yes
¹ The module sets the DTC 1 minute after it detects the condition.
Action Taken When the DTC SetsThe 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.
DTC B1440Step
Action
Yes
No
Schematic Reference: Body Control System Schematics
Connector End View Reference: Computer/Integrating Systems Connector End Views
1
Did you perform the Diagnostic System Check – Vehicle?
Go to
Step 2
Go to
Diagnostic System Check - Vehicle in Vehicle DTC Information
2
- Install a scan tool.
- Turn OFF the ignition.
- With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
- Ignition 0
- Ignition 1
- Ignition Accessory
Does the scan tool indicate that all inputs are Inactive/Off?
Go to
Step 3
Go to
Step 6
3
- 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 0
- Ignition 1
- Ignition Accessory
Does the scan tool indicate that the Ignition 0 and Ignition Accessory inputs are Active/On?
Go to
Step 4
Go to
Step 8
4
- Turn the ignition switch ON, with the engine OFF.
- With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
- Ignition 0
- Ignition 1
- Ignition Accessory
Does the scan tool indicate that the all inputs are Active/On?
Go to
Step 5
Go to
Step 8
5
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 0
- Ignition 1
- Ignition Accessory
Does the scan tool indicate that the Ignition 0 and Ignition 1 inputs are On and the Ignition Accessory input is inactive?
Go to
Step 11
Go to
Step 8
6
- Disconnect the ignition switch harness connectors.
- With a scan tool, monitor the following in Body Control Module, Data Display, Inputs:
- Ignition 0
- Ignition 1
- Ignition Accessory
Does the scan tool indicate that any of the Ignition 0, Ignition 1 or Ignition Accessory inputs is Active/On?
Go to
Step 7
Go to
Step 9
7
- 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 in Wiring Systems.
Did you find and correct the condition?
Go to
Step 14
Go to
Step 11
8
- 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 0
- Ignition 1
- Ignition Accessory
Does the scan tool indicate that the suspect circuits are now Active/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
- 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 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 BCM 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 BCM . Refer to
Control Module References for replacement, setup, and programming.
Did you complete the replacement?
Go to
Step 14
—
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
