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Ask Chad Farhat Your Own Question
Chad Farhat
Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems
Category: Buick
Satisfied Customers: 2783
Experience:  Owner at Carolina Auto Service & Sales , 20 years Experience in Foreign & Domestic vehicles
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2006 buick lacurne key was stuck in ignition after driving

Customer Question

2006 buick lacurne key was stuck in ignition after driving to the vet car was working fine came out then key wouldnt come out or start i got the key out replaced the weak battery but still no start . the only code is u0140 loss of communication with the body control module checked all fusses they are good
Submitted: 3 months ago.
Category: Buick
Expert:  Chad Farhat replied 3 months ago.

Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP.

Expert:  Chad Farhat replied 3 months ago.

Hey how are you

1-Please click on the blue link to view diagram

2- DTC U0140

Circuit/System Description Modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module. The body control module (BCM) activates the high speed GMLAN serial data wake up and the accessory wake up serial data circuits by applying voltage when the ignition key is in ACC, ON or START. The high speed GMLAN serial data wake up circuit wakes up the electronic brake control module (EBCM) for bus communication and the accessory wake up serial data circuit wakes up the engine control module (ECM) and transmission control module (TCM) Conditions for Running the DTC - The system voltage is between 9-16 volts. - The vehicle power mode requires serial data communication to occur. Conditions for Setting the DTC A supervised periodic message that includes the transmitter module availability has not been received. Action Taken When the DTC Sets The module uses a default value for the missing parameters. 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 - Use the DTC Descriptor list above to determine the module which is not communicating. - If there are multiple non-communicating modules choose the one closest to the data link connector (DLC). - Use Data Link References to determine if the module uses high or low speed GMLAN serial data communications - Some modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no module output voltage circuit is shorted to ground before replacing the module. - This diagnostic can be used for any module that should communicate with high or low speed GMLAN serial data providing the vehicle is equipped with the option that uses that module. Circuit/System Testing Important: If more than one module is not communicating use Data Link Connector Schematics to determine which module is closest to the DLC. Start diagnostics with that module. 1. Using the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested. 2. Ignition OFF, disconnect the harness connector of the module that is not communicating. Important: Only the high speed GMLAN modules have a wired serial data wake up circuit. Refer to the module schematics to identify which modules have a wake up circuit. If the module that is not communicating does not have a serial data wake up circuit, proceed to step 4. 3. Ignition ON, verify that a test lamp illuminates between the high speed GMLAN serial data wake up circuit OR the accessory wake up serial data circuit and ground. - If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM. 4. Ignition ON, verify that a test lamp illuminates between all battery positive voltage circuits and ground. - If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module. 5. Verify that a test lamp illuminates between all ignition voltage circuits and ground. - If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module. 6. Test for less than 1 ohm between the module ground circuits and ground. - If greater than 1 ohm, repair the ground circuit for an open. 7. Test for less than 1 ohm in the GMLAN serial data circuit(s) between the non-communicating module and the module that displays the DTC. - If greater than 1 ohm, test the GMLAN serial data circuit(s) for open/high resistance. 8. If all circuits test normal, replace the module that is not communicating. Repair Instructions Perform the Diagnostic Repair Verification after completing the diagnostic procedure. - GMLAN Wiring Repairs - Control Module References for module replacement, setup, and programming

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But let Try A master Reset first then we can move forward if it does not work

Master reset Procedure

1- Disconnect Battery Cables ( Negative & Positive Cables )you can use any electrical wire as an extension if battery cables don't reach .

2- Hold cables Together for 60 secs ,then let go

3- Wait 15 minutes

4- Make sure all doors are closed

5- Reconnect battery Cables

6- Lock & unlock the vehicles using the key from driver door side (if you have a key fob with no blade key, just lock & unlock using the key fob buttons)

7- Enter the vehicle and attempt to start

Please let me know

Thank You

Chad Farhat

ASE Certified Technician

Expert:  Chad Farhat replied 3 months ago.

Hi, just checking in ,to see how things are going,Do you need further assistance ?

Please let me know if you need anything else on it, just reply back and we will continue

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Thank You
Chad Farhat
ASE Certified Technician