P0700 Error

[Enjnan]

I am extremely limited on my mechanical knowledge so I will start by saying that!

2003 Chevy Silverado 2500HD, Diesel.

About 3 miles from home it started driving rough and check engine light came on. Got 3 errors

P0700
U2106
P0404

Not worried about the last code (EGR, have replaced it and it still intermittently comes and goes). Worried about the other 2.

Is there any diagnostics I can do at home before needing to take this to the shop? I can do little stuff like testing fuses, but can't disassemble something major.

Just spent 3k on this thing for power steering problems. Really trying to avoid the shop if at all possible.

Thanks!

[DmaxMaverick]

Welcome aboard!

P0700 - ONLY a PCM (powertrain/engine computer) code indicating that the TCM (transmission computer) has a code, and commands the MIL (Malfunction Indicator Lamp). Nothing else. You'll need to use a scanner capable of reading TCM codes to get the TCM code that triggered the P0700. Not a real big deal if you wait for it to self-clear, but it will usually take a bunch of warm-up cycles for it to happen. If the tranny is performing normally, give it some time to clear itself. In the meantime, check the fluid level and other routine maintenance items.

U2106 - Transmission communication error. Check transmission electrical connections at the tranny, and the NSBU (box where the shift linkage connects). Remove, check (clean if necessary, with electrical contact cleaner aerosol), apply some dielectric (tune-up) grease, reconnect firmly. If code returns after clearing, with no additional new codes, disconnect BOTH battery power and ground cables, and do the same at the TCM (located on the driver side, next to the radiator). While ALL cables are disconnected from BOTH batteries, ground one Batt+ cable to chassis or ground cable for at least 30 minutes (this will default the computers and clear all but most recent codes in history, if still active). Check battery voltage of each battery individually after 30 minutes, then reconnect if voltage is good (12.6V or greater each, within 0.2V between them).

[DmaxMaverick]

Also, if you are using an Edge, or any other power mod that connects to the PCM connector, remove it. At least until your diagnostic and correction is complete. Check the connector and verify none of the pins are damaged or misaligned.

[Enjnan]

Thank you, that is a great post. I appreciate the info! I will see what I can figure out!

Do you have a recommendation for a scanner?

[DmaxMaverick]

You're welcome.

I don't recommend a scanner, specifically, but find a local shop (or sometimes a dealer) that will read them for some pocket change (it only takes a minute or two). A good scanner is north of a grand, so $5-20 at a shot goes a LONG way. The chain stores that advertise code reading will read what you already know, and nothing more. I have a friend with a Tech-II who owns a shop local to me, so we trade skills. Otherwise, if you're serious about DIY, keep an eye out for an affordable Tech-II on Ebay (not often, but they come up). As long as it's updated to your model year, it'll see everything the dealer can.