Engine Power Is Reduced - Ongoing Issue, Updates throughout thread.

[Mighty Hd]

Vehicle is a 2013 Tahoe LT Z71 with 90k. Max towing pkg, two speed transfer case (2hi, 4hi, 4low & auto 4wd).

Fuel pump failed and also the fuel pump control module. I swapped the fuel pump today and I’m waiting on the FPCM to arrive at the local dealer.

I checked the modules and noticed there are quite a number of codes on the transfer case module, however the 4wd works fine and shifts smoothly. All bi-directional tests, actuator test, etc passed.

Codes C0321 - Range actuator engagement control circuit short to battery..

C0379 - Front axle engagement system short to battery.

B0770 - 4wd auto range indicator control circuit short to battery

B0775 - 4wd high range indicator control circuit short to battery

B0780 - 4wd low range indicator control circuit short to battery

B0790 - Transfer case neutral range indicator control circuit short to battery

C0374 - General system performance temperature high

U0073 - Control Module communication BUS off invalid data

Fuel pump module now only has:’P0606 indicating an internal failure on the module.

I cleaned the ground wires to the engine block from the battery. Ground strap on driver side head to the firewall Ground wires on the frame mount under the driver door Ground wires on the driver side last body mount.

Transfer case encoder was plugged in, no signs of any damaged wiring or wire loom.

I’m not sure what do do at this point. Any suggestions?

 

[swathdiver]

Vehicle is a 2013 Tahoe LT Z71 with 90k. Max towing pkg, two speed transfer case (2hi, 4hi, 4low & auto 4wd).

Fuel pump failed and also the fuel pump control module. I swapped the fuel pump today and I’m waiting on the FPCM to arrive at the local dealer.

I checked the modules and noticed there are quite a number of codes on the transfer case module, however the 4wd works fine and shifts smoothly. All bi-directional tests, actuator test, etc passed.

Codes C0321 - Range actuator engagement control circuit short to battery..

C0379 - Front axle engagement system short to battery.

B0770 - 4wd auto range indicator control circuit short to battery

B0775 - 4wd high range indicator control circuit short to battery

B0780 - 4wd low range indicator control circuit short to battery

B0790 - Transfer case neutral range indicator control circuit short to battery

C0374 - General system performance temperature high

U0073 - Control Module communication BUS off invalid data

Fuel pump module now only has:’P0606 indicating an internal failure on the module.

I cleaned the ground wires to the engine block from the battery. Ground strap on driver side head to the firewall Ground wires on the frame mount under the driver door Ground wires on the driver side last body mount.

Transfer case encoder was plugged in, no signs of any damaged wiring or wire loom.

I’m not sure what do do at this point. Any suggestions?

Any critters chewing on your wiring harnesses? When we see multiple codes across several different areas it is usually an electrical problem. First culprit is usually a tired, worn out battery, or a battery that pasts tests but has a bad cell. Next up are the battery cables and grounds. Then critters chewing on the wires. I find it odd that the pump and module went out at the same and then the controller for the transfer case went too. Could she have been struck by lightning?

I got a code for the tc switch recently, cleared it and it kept on working just fine. Replaced it anyway because I didn't want an issue when might really need it.

 

[Doubeleive]

sounds like a shorted wire or circuit somewhere, you might try poking around for any service bulletins noting those codes and hopefully pointing to a potential area to look/inspect.

 

[Mighty Hd]

So I got the fuel pump control module replaced and programmed today, those codes are now clear.

Verified that the 4wd system works. No CEL/service 4wd light illuminated; for $15, I swapped the selector switch and also did a relearn on the encoder motor. All bi-directional tests operate as they should.

Checked the ground again by the driver door body mount and it’s clean as a whistle. No wires are pinched, no rubbing underneath or within the dash.

If it were the TCCM, the 4wd system would not function / or be unable to bidirectionally communicate with the module.
Grrrr

 

[Mighty Hd]

Oh. Battery is a year old. I have the hall monitor unplugged and has been for several years now. That stopped my annual battery replacement issue.

Cables are clean and tight.

Stored in the garage, no critters or bugs.

 

[Mighty Hd]

Any critters chewing on your wiring harnesses? When we see multiple codes across several different areas it is usually an electrical problem. First culprit is usually a tired, worn out battery, or a battery that pasts tests but has a bad cell. Next up are the battery cables and grounds. Then critters chewing on the wires. I find it odd that the pump and module went out at the same and then the controller for the transfer case went too. Could she have been struck by lightning?

I got a code for the tc switch recently, cleared it and it kept on working just fine. Replaced it anyway because I didn't want an issue when might really need it.

When I replaced the fuel pump module assembly, there were very fine metal flakes clogging the sock and all around the bottom of the white module cup that contains the pump.

The dealer advised today that most likely the pump motor was the culprit. As a result the pu p probably pulled too many amps for too long, thus burning up the.pump control module.

It’s running like a scalded dog now…just need to get the other codes addressed.

 

[Fless]

It looks to me like the 4x4 codes indicate that the system is seeing high voltage on the encoder circuit coming out of the TCCM/ATCM. Have you measured the voltage (typically 5v, but I'm not specifically familiar with your system) that the TCCM provides to the switch and encoder circuit? A Tech 2 scanner would show you what the supplied voltage is, as well as the voltages that the various modes send back by the encoder motor.

The circuit voltage can be measured at the dash mode switch harness, for starters; then at the T/C connector. One cause could be a 12v wire rubbing on the reference voltage circuit. Also disconnect, inspect, and clean the encoder circuit connectors if that hasn't been done yet.

EDIT: don't necessarily assume that the TCCM is good; further diagnostics should be done to confirm. You'll likely need a wiring diagram from AllDataDIY or similar, with troubleshooting steps for the specific codes.

 

[Mighty Hd]

I checked every connector, every ground that I could possibly find..and cleaned them well. Same codes are being stored in the TCCM.

I also attempted to connect the ground under the driver side door directly to the battery and I'm still getting the same codes. Also cleaned all the electrical connections on the transfer case using compressed air and reassembled. No signs of corrosion on any of the connectors.

Checked most all of the underhood wiring harness and no indications of frayed wiring; removed the lower portion of the dashboard on teh driver side and confirmed the TCCM wires were not pinched or frayed.

The 4wd actuator switch lights all illuminate and the 4wd cycles through all modes fine (2wd, auto, 4hi, 4lo and neutral.

Using a foxwell bi-directional, I can manually engage the front axle actuator, cycle the encoder motor, etc.

I'm really scratching my head here as the system functions fine..yet it's showing codes in the TCCM.

I'm half tempted to say F-it as the system does work....

 

[George B]

Related but not sure it has much value.

Codes b0770,b0775,b0780,b0785 indicator circuit short to ground/open

hi all , these came up on a scan which was done to see if any thing popped up with a vibration on pulling off from a stop and traction control comming on while turning still need to short those issues but no lights on dash but these codes keep comming back just seeing if any one has dealt with...

www.tahoeyukonforum.com

 

[Fless]

I checked every connector, every ground that I could possibly find..and cleaned them well. Same codes are being stored in the TCCM.

I also attempted to connect the ground under the driver side door directly to the battery and I'm still getting the same codes. Also cleaned all the electrical connections on the transfer case using compressed air and reassembled. No signs of corrosion on any of the connectors.

Checked most all of the underhood wiring harness and no indications of frayed wiring; removed the lower portion of the dashboard on teh driver side and confirmed the TCCM wires were not pinched or frayed.

The 4wd actuator switch lights all illuminate and the 4wd cycles through all modes fine (2wd, auto, 4hi, 4lo and neutral.

Using a foxwell bi-directional, I can manually engage the front axle actuator, cycle the encoder motor, etc.

I'm really scratching my head here as the system functions fine..yet it's showing codes in the TCCM.

I'm half tempted to say F-it as the system does work....

After you're done scratching your head, and when you get to the point of using a voltmeter (or a Tech 2, which should show this in the T/C data), check the reference circuit voltage at the switch, both connected to and disconnected from the switch. The TCCM doesn't send 12v to the reference circuit. If it does, it's defective.