My code reader is reading U-0077 . No engine light is on .
Minor complaints -- Idle a little rough-- Some stumble in 7th gear on acceleration
Any ideas?

 

That's a power steering position sensor code. Shouldn't have anything to do with the engine.

 

see if this helps any: http://u0077.enginetroublecode.com/

I'm surprised you didn't get a check engine light, a misfire code, or a service transaxle (puts the car in nanny mode to protect the car from a faulting engine) The service transaxle may briefly show in the center of your speedo, depending on how you have set up your display.

Loose plug wires Loose connectors to coil packs, MAF, etc. Have you removed the air filter box lately? loose leaking connection at TB allowing more air in.

 

Did you actually read that page? It contradicts itself multiple times, sometimes in the same sentence. It's almost gibberish.

According to my AllData subscription, which draws directly from GM's official service info, this code is for an error on the chassis expansion data bus. DTC U0077 00

• Control Module Communication Chassis Expansion CAN Bus Off

The chassis expansion bus has the following modules.
Brake control
Power steering
Magnetic suspension
Rear differential
Chassis control
Steering angle
Airbags

 

FYI - alot of information on the web points to the engine misfiring in the wrong or altered sequence.

Some other possibilities

U0002-HIGH SPEED CAN COMMUNICATION BUS PERFORMANCE
U0077-CONTROL MODULE COMMUNICATION BUS OFF
Both of these are codes for loss of communication from the Body Control Module(BCM) to the Engine Control Module(ECM).
This can by from a fault in the communication data lines, or more commonly, a faulty BCM


Symptoms of a U0077 diagnostic trouble code may include:

• Blown fuse (if applicable)
• Engine surge
• Reduction in engine performance, especially at low RPM levels
• The light may stay on or light intermittently as the DPF regenerates. The engine will be sluggish on acceleration.

Possible Causes :

• An air leak forward of the DPF will change the sensor readings resulting in the code
• Rusty exhaust systems, cracked exhaust manifolds or damaged or missing gaskets or donuts will cause air leaks.
• Dirty air cleaner element Damaged DPF

 

It's probably nothing. Clear the code and drive the car. If the code returns, let us know.

 

DPF = diesel particulate filter....

 

After I found the code, I removed the air cleaner, blew it out (only 9000 miles looks new)Cleaned the throttle body, some dirt not that bad. Idle is about the same a little rough, I keep being told "that's normal" Acceleration in 7th gear now a ok. Code gone from reader , just in memory.
I also checked all plug and coil wires even the side thats impossible to get to!
Thanks to all for their input.
Al

 

My C7 is rough at cold start and was sometimes really rough when I had a loose plug wire. It never threw a CEL, but, one track day put it in nannie mode and smoked a rear caliper of all things. I posted about this back in March or so.

The engine should smooth out after a warmup. Everything is connected to everything else, and the LT engines use the Crank Position Sensor to detect and post misfires. Depending on what is causing a misfire (any rough idle or lack of power, unless the brakes are actuated should be SOME sort of misfire), it may or may not throw a misfire code per se. Gas engines haven't really changed that much since Nick A. Otto came up with the 4 stroke gas engine. They need fuel, air, and an ignition source. Short change any of these and you will start misfiring.

Your code may be a loose connection somewhere, probably in the engine bay that is giving that code, which is a pretty unusual code to say the least. Troubleshooting these cars is like a dentist going through your rectum to clean your teeth, so a little patience and small fingers may be needed to solve this one. By all means be kind to the patient.

That being said, keep looking and finding. My guess is you ain't dun yet. Good start, you solved one issue.

If you have PDR on your C7 take it out and record a street session. You can use the Cosworth Toolbox to compare runs. I think you can set it to compare 0-60 runs, etc.

 

That is gruesome, yet accurate...