TAC MODULE?

[Maximus1]

Pardon my rant:
This is probably the most frustrating problem I have ever experienced as a mechanic for the past 20 years. 2004 Tahoe 5.3L L59 Flex fuel engine with a drive by wire setup which by the way the dumbest thing GM ever did and is also the reason for my problem. Yes it could all be fix with a simple throttle cable, stupid stupid stupid. I also don't understand the stupid reason for removing the dependable throttle cable and replacing it with unreliable electrical wires and parts from China, again STUPID!!!!!
Anyways..... codes as follows
U0107 lost communication with TAC module

P2108 TAC module performance

P1516 intake manifold runner control input error

I've replaced the throttle body position sensor twice and replaced the pigtail to the throttle body twice which was a recall by GM.

Replaced the gas pedal sensor twice and also checked the wiring from the pedal to the TAC module and from the module to the throttle body and all looks good.

My last and only solution is to replace the TAC module itself. The reason for this being last and I'm hesitant to do the replacement is that it's expensive at $241 and I've been told that this is very rarely the actual problem like 1 in 50,000 modules.

Does anyone have any other ideas for the trouble codes I have before I replace the TAC module? Any help or information is welcome and greatly appreciated.

I will update this post when I find and correct the problem. Thanks

 

[Maximus1]

Here's a picture of the TAC module. It's located on the driver side firewall under the hood.

 

[retiredsparky]

A couple of thoughts:
Would it be worthwhile to check your grounds for corrosion/looseness? Maybe add a couple if you can't find one from engine to cab and cab to frame.

How old is your battery? I have fixed unexplained GM problems in Silverado's, equinox and tahoes by replacing supposedly good batteries, even when the batteries started and tested fine. Try swapping a temporary battery.

Clean your battery terminals.

Put a multimeter on the alternator output and check for AC voltage.

If the mounting plate is used as a ground for the module, make sure that at least one of the mounting screws is corrosion free. Any resistance in the power supply circuit for modules can vary and cause noise on the communication buss between the various modules.

Pull the connectors off the ECU/ECM behind the battery and check for corrosion.

Make a breakout terminal and pull the fuse that feeds power for the throttle control so you can verify operating voltage with the fuse plugged back in.

Has the car been used to jump a dead battery in another vehicle?

Etc.

Larry

 

[Maximus1]

Thanks Larry, I'm going to check the grounds today. I know that there is a major ground for the wiring harnesses on the back of the engine that I'm going to remove and clean. I also added a ground from the battery to the front of the cylinder head

 

[Maximus1]

A couple of thoughts:
Would it be worthwhile to check your grounds for corrosion/looseness? Maybe add a couple if you can't find one from engine to cab and cab to frame.

How old is your battery? I have fixed unexplained GM problems in Silverado's, equinox and tahoes by replacing supposedly good batteries, even when the batteries started and tested fine. Try swapping a temporary battery.

Clean your battery terminals.

Put a multimeter on the alternator output and check for AC voltage.

If the mounting plate is used as a ground for the module, make sure that at least one of the mounting screws is corrosion free. Any resistance in the power supply circuit for modules can vary and cause noise on the communication buss between the various modules.

Pull the connectors off the ECU/ECM behind the battery and check for corrosion.

Make a breakout terminal and pull the fuse that feeds power for the throttle control so you can verify operating voltage with the fuse plugged back in.

Has the car been used to jump a dead battery in another vehicle?

Etc.

Larry

My battery is about 1-1/2 years old. While checking the battery I noticed that the negative terminal was loose and would not tighten because it was stripped out. I replaced the terminal bolt and now it's tight.

I also removed the terminal plugs from the ECM and noticed that a few of wires looked dirty so I cleaned them. Here's a picture

I'm not 100% sure if this fixed my intermittent problem but it needed to be cleaned anyways.

 

[Maximus1]

Ok so I removed the harness ground wire from the back of the engine and it looks like it wasn't grounding very good so I cut off the connector and spliced it to make it longer then I attached it to an extra grounding wire I had made awhile back and it's bolted to the front of the engine and then directly to the negative side of the battery. The throttle seems to be a lot more responsive than before and no codes so far. This problem seems to be a grounding issue and not a module issue. Glad I didn't spend $241 on a new module. Thanks Larry for your help. Your advice is what I was thinking but I just needed that push to check all the wires again. Here's some pictures

 

[Maximus1]

A couple of thoughts:
Would it be worthwhile to check your grounds for corrosion/looseness? Maybe add a couple if you can't find one from engine to cab and cab to frame.

How old is your battery? I have fixed unexplained GM problems in Silverado's, equinox and tahoes by replacing supposedly good batteries, even when the batteries started and tested fine. Try swapping a temporary battery.

Clean your battery terminals.

Put a multimeter on the alternator output and check for AC voltage.

If the mounting plate is used as a ground for the module, make sure that at least one of the mounting screws is corrosion free. Any resistance in the power supply circuit for modules can vary and cause noise on the communication buss between the various modules.

Pull the connectors off the ECU/ECM behind the battery and check for corrosion.

Make a breakout terminal and pull the fuse that feeds power for the throttle control so you can verify operating voltage with the fuse plugged back in.

Has the car been used to jump a dead battery in another vehicle?

Etc.

Larry

Do you know where the small negative battery cable connects to? The negative cable is a two in one cable. I know that the bigger fat one connects to the engine block but I'm not sure where the smaller one connects to.