Diesel Place banner

1 - 8 of 8 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
Last summer I was driving in the rain and my van died, I tried to start it back up and all it would do is click. Towed it back home and got looking around and seen my fuse box was wet and didn't have a cover so I replaced the whole fuse box under the hood. Still wouldn't start. So I started cleaning all the ground wires I could find on the motor and frame and that ended up letting it start, but now I've been dealing with having to take the rear fog light fuse in and out so the battery won't drain. So when its a nice clear day I can leave the fuse out and the van will run fine and everything but the wipers don't work and it has a code B1440(Power Mode Master Input Circuits Mismatched). So if it rains I have to put the fuse back in so my wipers will work, kinda a pain, but then I have to take it back out if I'm gonna leave it sitting over night cause the radio stays on and the battery light stays on and the gear selector. Also with the fuse out the acc doesn't work and the warning lights don't come on until after the van runs for 3-5 seconds. I replaced the ignition switch and still have the same problem so I was wondering if there was something else anybody could recommend I do before buying a new BCM.
 

·
Administrator
Joined
·
15,966 Posts
Welcome to DieselPlace

:thumb:
 

·
Registered
Joined
·
2,528 Posts
This info is specific t omy 2008 model, yours will be similar. Pls PM your email address to me for more info.

DTC B1440

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection\Initial Inspection and Diagnostic Overview
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B1440 00

Power Mode Master Input Circuits Mismatch

Diagnostic Fault Information



Circuit/System Description

This vehicles power mode master (PMM) is the body control module (BCM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determination of the power mode. The PMM receives the ignition switch signals, and additionally a reference voltage signal from the BCM, through the ignition switch, and back to the BCM. There are redundancies within the PMM system that can allow operation of certain subsystems when there are faults in the ignition switch circuits. Other information such as serial data input from other modules and DTCs is also used to determine what power mode signals and information is transmitted by the PMM. The BCM logic uses all this information to identify the operators desired power mode and activate specific discrete signals, and serial data messages for the operation of many different subsystems as necessary. Other modules which have switched voltage inputs may operate in a default mode if the PMM serial data message does not match what the individual module can see from its own connections.

The PMM will activate relays and other direct outputs of the PMM as needed according to the calculated power mode. Several relays controlled by the BCM are switched ignition voltage outputs the are pass through circuits within the BCM directly from the ignition switch. If these circuits short to ground, the fuse to the ignition switch will open.

Conditions for Running the DTC

Ignition switch is in the RUN position.

Conditions for Setting the DTC

BCM senses an open or short to voltage on the off/run/crank voltage circuit when both ignition accessory/run and ignition run/crank parameters are active.
BCM senses an open on the battery positive voltage circuit (to the ignition switch) while engine is running. An open on the battery voltage circuit can be caused by a short to ground on any of the following circuits:
Battery positive voltage
Accessory voltage
Run/crank ignition 1 voltage
Off/run/crank voltage

Action Taken When the DTC Sets

The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the GMLAN serial data communications circuits.
The other modules on the vehicle operate in a fail-safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the GMLAN serial data communications circuits.
The vehicle may not start.

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 of 50, without a repeat of the malfunction.

Diagnostic Aids

A short to ground in the accessory wakeup serial data circuit will cause an open fuse to the ignition switch. DTC U1814 should be current.
A short to ground in the run/crank ignition 1 voltage circuit of the run crank relay will cause an open fuse to the ignition switch. DTC B1428 should be current.
The power modes and controls are determined using BCM logic. Comparing the Body Control Module Power Mode data display parameters listed in Circuit/System Verification will determine if there is a power mode fault.

Circuit/System Verification

Verify that the following DTCs are not set: U1814, B1428.

If either of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. See: Diagnostic Trouble Code Descriptions

With a scan tool, access Body Control Module, Power Mode data display list and compare all parameters listed with the corresponding ignition key position. The PMM Power Mode Parameters table below illustrates the correct state of these input parameters (circuits) in correspondence to the ignition switch position. The circuits which the individual parameters are related to are in parentheses.



Circuit/System Testing

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

Inspect for an open Ign Switch fuse. The fuse should be OK.

If the fuse is open, test the following circuits for a short to ground, if all circuits test OK, replace the BCM.
Battery positive voltage of the ignition switch
Accessory voltage
Off/Run/Crank voltage
Ignition 1 voltage
Accessory wakeup serial data (BCM output)
Run/crank ignition 1 voltage (BCM output)

Disconnect the harness connector at the ignition switch.
Verify that a test lamp illuminates between the B+ circuit terminal 4 and ground.

If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

Important: The ignition switch component test must be preformed before proceeding with this test to verify the integrity of the switch.

Perform the ignition switch component test. The test should pass.

If the ignition switch fails, replace the ignition switch.

Ignition OFF, disconnect the X 1 harness connector at the BCM, test for less than 1.0 volt between the following circuit terminals of the BCM and ground.

Ignition key resistor signal terminal 4
Off/Run/Crank voltage terminal 2
Accessory voltage terminal 21
Ignition 1 voltage terminal 14
If greater than specified, test the circuit for a short to voltage.

Test for less than 1.0 ohm of resistance between the BCM and the ignition switch on the following circuit terminals.

Ignition key resistor signal, BCM terminal 4 and ignition switch terminal 6
Off/Run/Crank voltage, BCM terminal 2 and ignition switch terminal 5
Accessory voltage, BCM terminal 21 and ignition switch terminal 3
Ignition 1 voltage, BCM terminal 14 and ignition switch terminal 2
If greater than 1 ohm, repair the circuit for open/high resistance

Test for infinite resistance between the ignition key resistor signal circuit terminal 4 of the BCM and ground.

If less than specified, repair the signal circuit for a short to ground.

If all circuits test normal, replace the BCM.

Component Testing

Ignition Switch

Ignition OFF, disconnect the harness connector at the ignition switch.
Using the Resistance Test table below, check the resistance between the terminals of the ignition switch listed in each switch position.



If any reading is not as specified, replace the ignition switch.

Repair Instructions
 

·
Registered
Joined
·
3,490 Posts
Here is test steps for 2006 van.
 

Attachments

  • Like
Reactions: Ron Nielson

·
Registered
Joined
·
3,490 Posts
Does anyone happen to have a diagram for the wires on the BCM?
Get yourself a subscription to Alldatadiy. It is cheap and contains a lot of helpful info like this.

Sent from my XT1710-02 using Tapatalk
 
  • Like
Reactions: LCAC_Man
1 - 8 of 8 Posts
Top