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Im a used car dealer. Just purchased a 2008 chevy tahoe

Customer Question
Hi Tom , Im...

Hi Tom , Im a used car dealer. Just purchased a 2008 chevy tahoe hybrid with 144k miles . My problem is that it will not start.I put the key in the ignition , turn it to the run position, everything lights up in the speedo cluster. turn the key to start position and the speedo cluster goes dead and engine does not start. replaced the battery with a new one to ensure that the vehicle has correct operating voltage. all power windows, lights, radio, door locks , blower motor and horn are functioning correctly. these are the obd codes that I pulled up. BO790, UO100, UO101, UO140, UO121 and UO131. Any help in figuring out this problem would be greatfuly appreciated

Mechanic's Assistant: Have you checked the fuses? Have you checked the door switches?

Yes checked all these fuses. Door swiches? Interior lights go out when I close drivers door. By the way, my name is*****: Are you fixing your Tahoe Hybrid yourself? What have you tried so far?

Trying to .I've been in the used car business and repairing cars for 30 years now. Replaced the battery. Checked all fuses

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

No, I think I have covered everything so far. The vehicle is extremely clean Inside and out.

Submitted: 10 months ago.Category: Chevy
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Answered in 4 days by:
10/10/2017
Chevy Mechanic: Lou P., ASE Certified Technician replied 10 months ago
Lou P.
Lou P., ASE Certified Technician
Category: Chevy
Satisfied Customers: 6,263
Experience: Building and driving Chevy's since I was in the womb!!!! Camaro and Corvette enthusiast, access to factory diagrams and tsb's
Verified

Hello, my name is***** and i will do my best to assist you.I am going over your story now and will reply back soon with some info,thanks!

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Chevy Mechanic: Lou P., ASE Certified Technician replied 10 months ago

DTC B0790 Diagnostic Instructions * Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. * Review Strategy Based Diagnosis for an overview of the diagnostic approach. * Diagnostic Procedure Instructions provides an overview of each diagnostic category. DTC Descriptor DTC B0790 01 - Neutral Indicator Circuit Short to Battery DTC B0790 06 - Neutral Indicator Circuit Short to Ground or Open Diagnostic Fault Information

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Circuit/System Description

The neutral indicator circuit consists of an ignition 1 voltage circuit and a neutral indicator control circuit. When the neutral mode has been selected, current is supplied to the neutral indicator by the ignition 1 voltage circuit, traveling through the neutral indicator LED, at which time the transfer case shift control module supplies the ground through the neutral indicator control circuit.

Conditions for Running the DTC

* The ignition is ON.
* System voltage is 10-18 volts.

Conditions for Setting the DTC

* The system monitors the voltage on the neutral indicator control circuit.
* If the system detects a voltage of 2 volts or less for 1.5 seconds when the 2 high indicator is not commanded, the DTC is logged.
* If the system detects a voltage of 4.5 volts or more when the 2 high indicator is commanded, the DTC is logged.

Action Taken When the DTC Sets

The SERVICE 4WD indicator is commanded on for this DTC for the remainder of the ignition cycle.

Conditions for Clearing the DTC

* The transfer case shift control module clears the DTC if the condition for setting the DTC is not currently present.
* A history DTC clears after 40 consecutive warm up cycles without a fault present.
* History DTCs can be cleared using a scan tool.

Reference Information
Schematic Reference

Transfer Case Control Schematics ( See: Transfer Case > Electrical > Transfer Case Control Schematics)
Connector End View Reference

Component Connector End Views
Electrical Information Reference

* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs

Scan Tool Reference

* Scan Tool Data List ( See: Transfer Case > Scan Tool Testing and Procedures > Scan Tool Data List)
* Scan Tool Data Definitions ( See: Transfer Case > Scan Tool Testing and Procedures > Scan Tool Data Definitions)

Diagnostic Aids

A short to ground on the neutral indicator control circuit will cause the neutral indicator to remain on at all times. An open or high resistance will cause the neutral indicator to be inoperative during the 2 second bulb check.

Circuit/System Testing

Check the ignition 12 voltage reference circuit pin 2 at the transfer case shift control switch for voltage with the ignition on.

If less than battery voltage check the 12 volt reference circuit pin 14 at the BCM and pin 2 on the transfer case mode switch for an open or high resistance. If the voltage is low or non existent and the circuit tests good replace the BCM. If the BCM test good go to the next step.

If the neutral indicator is on at all times check the neutral indicator control circuit for a short to ground. If the neutral indicator is inoperative during bulb check, check the neutral indicator control circuit for an open or high resistance or short to voltage. If the circuit checks good continue to the next step.

With the ignition on shift the transmission to neutral and using transfer case output controls attempt to command the neutral indicator off and on. If the neutral indicator is still inoperative short to neutral indicator control to ground, if the neutral indicator lights replace the module, program, and complete the motor learn procedure. If the neutral indicator is still inoperative replace the switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

* Transfer Case Shift Control Switch Replacement (Without SLT) ( See: Four Wheel Drive Selector Switch > Removal and Replacement > Transfer Case Shift Control Switch Replacement (Without SLT))Transfer Case Shift Control Switch Replacement (With SLT) ( See: Four Wheel Drive Selector Switch > Removal and Replacement > Transfer Case Shift Control Switch Replacement (With SLT))
* Control Module References for TCSCM replacement, setup, and programming
* Transfer Case High/Low Clutch Reset ( See: Transfer Case > Symptom Related Diagnostic Procedures > Transfer Case High/Low Clutch Reset)

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Chevy Mechanic: Lou P., ASE Certified Technician replied 10 months ago

DTC U0100 00 - Lost Communication With ECM/PCM

DTC U0101 00 - Lost Communication With TCM

DTC U0121 00 - Lost Communication With Anti-Lock Brake System (ABS) Control Module

DTC U0140 00 - Lost Communication With Body Control Module

I do not see a U0131

so we have a diagnostic wire issue,

I need you see if you can tell what control modules have those codes in them.

them we need to disconnect each module one at a time and recheck to see if it truck will start.

a bad module or shorted wire will kill the communication system so the car will not know what gear its in and what not.

Lou

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Chevy Mechanic: Lou P., ASE Certified Technician replied 9 months ago

I have taken my time to answer your question the best I could and I will continue to help if you need follow up information , all I ask is that you PLEASE take a second to rate my service so I may receive my credit for assisting you. the only way I am paid for my info and time is when you rate, if there is a issue with the info I sent and you need more help or anything then by all means please let me know and I will continue to help you, but please take the time to rate me so I may be paid. Thank you. Lou P.

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