Question: Three OBD Codes
- Thread starter pthib1
- Start date
P0700 is not going to help much, you need a better scanner. P0700 is just a code that tells you something in the transmission area is maulfunctioning. It doesn't tell you what is actually not operating properly
Here's a trouble code master list from edge, it's something like 48 pages...
http://www.edgeproducts.com/product_images/customer_support_article-pdf-40.pdf
Have fun:thumb:
http://www.edgeproducts.com/product_images/customer_support_article-pdf-40.pdf
Have fun:thumb:
Those all may be related, actually. The U2104 & U2105 are the ECU saying it is having trouble communicating on the CAN bus. The transmission is probably storing a similar code, and since it requires engine data to shift right, etc., it set the P0700.
There are 2 separate buses on the 2003. The GMLAN low-speed bus (which goes to the diagnostic port in the cab, stereo, door computers, etc.) and the proper CAN bus, which on the LB7 only goes from the engine computer to the transmission computer.
U2xxx codes appear to relate to the CAN bus, and U1xxx codes appear to be GMLAN, IIRC.
So, I would look at the condition of the wiring from the ECU to the TCM. There may be a pinched or loose wire.
A better scan tool would help to confirm what code(s) the TCM has.
There are 2 separate buses on the 2003. The GMLAN low-speed bus (which goes to the diagnostic port in the cab, stereo, door computers, etc.) and the proper CAN bus, which on the LB7 only goes from the engine computer to the transmission computer.
U2xxx codes appear to relate to the CAN bus, and U1xxx codes appear to be GMLAN, IIRC.
So, I would look at the condition of the wiring from the ECU to the TCM. There may be a pinched or loose wire.
A better scan tool would help to confirm what code(s) the TCM has.
Update
Initially the TCM was repalced. After a few days the codes returned as well as the shifting problem. Second step the FICM was replaced. Truck has been daily-driven for 5-days. No codes, and no shifting problems. I hope this helps anyone out there with similar issues.
Initially the TCM was repalced. After a few days the codes returned as well as the shifting problem. Second step the FICM was replaced. Truck has been daily-driven for 5-days. No codes, and no shifting problems. I hope this helps anyone out there with similar issues.
Check the harness where it passes behind the alternator. this is a known spot where the harness can fail and give these problems. When you replaced the FICM you probably just moved the harness, but the problem may still return. The high speed J1939 CAN BUS runs from the ECM, FICM, and TCM on 01-05 trucks. Then you have the low speed J1850 bus for the other on board modules as well as a 3rd data bus that goes in between the ECM and BCM for passlock security system. So there is actually 3 data buses in 01-05 trucks(learned about this one on my swap as I wanted to be able to run mine without having to disable the security in the ECM tuning).
Yeah, you are right, the CAN bus does go to the FICM too, I forgot about that.
But I thought the passlock security just used the low speed bus along with everything else? Now I curious, and I'll have to pull up the schematics when I get home.