2007 Tahoe won't start!

[mtrdrms]

Hi Everyone,

I've got a 2007 Tahoe LTZ that suddenly won't start. On Saturday night we were headed out shopping and the truck started fine but none of the instruments were working. When we came out of the store it wouldn't start. No crank at all. All lights seem to work and windows, locks, radio etc. all work. So I had it towed home and went after all the normal culprits that I thought might cause this. I removed and cleaned both the positive and negative batt cables, checked all fuses and relays and, yes, charged the battery up. Still nothing. Any suggestions?

Thanks!

Andy

[anumber1]

My best Internet guess; ignition switch.

[mtrdrms]

Thanks for the reply. This could very well be the problem. I am going to check for DTCs this afternoon and see if that can point me in the right direction. Do you know of a good test for the ignition switch?

[sefiroxx]

Bypass starter relay with a jumper from starter battery cable to the solenoid. If no crank, bad starter

 

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[mtrdrms]

Starter is good. Oddly, the obd port won't even power up my scan took??

[mtrdrms]

Ok, I found a bad aux pwr fuse and now the port works. I've got codes U0121 and U0140...

[Coby7]

U codes are communication codes that come up when one CPU can't communicate with an other.

 

DTC U0121 ___ Lost Communication With Anti-Lock Brake System (ABS) Control Module ( This should not stop your Tahoe from starting )

DTC U0140 ___ Lost Communication With Body Control Module ( But this one will )

 

Most common affliction for this is corrosion on the contact pins. Disconnect B+ cable at the battery ( While there check the fusible link for green stuff, BCM is fed through this fusible link ) Then disconnect cables from the BCM and re-seat them a few times to scuff and clean the contacts. Put everything together and try to start your Tahoe. If this doesn't work look for a broken or chaffed dark green wire. ( GMLan )

 

File is too big to load here but you can have a look at it in my DropBox. What you're looking for is pin 10 of connector ''C3'' low speed GMLan

 

https://www.dropbox.com/s/szpu3sckav045c9/2007%20Tahoe%20BCM.pdf?dl=0

[NBSFan]

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

[NBSFan]

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

[mtrdrms]

This is great information. I'll let you know what I find.

[Coby7]

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

 

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

 

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

 

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

 

Did you check your + & - battery cables for corrosion and good contacts at the starter, firewall and frame ? The cables are prone to corroding inside out (turning green) and they also corrode where the ground cables bolt to the firewall and frame.

 

U0121 = Elec Brake Control has lost communication

U0140= Body Control Module has lost communication

You really wanted to put your point across lol

[deepstuff]

Hi i have a 2007 LTZ. went after all the regular stuff but problem was the crimped on fitting on the positive battery cable. Cut it off and usdd a bolted together clamp style. Cut old fitting in half and could see the vurning caused by loose connection. That was two years ago. Last year did the same with the neg cable.

 

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