need some help with DTC's

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Jan 28, 2011 | 11:23 AM

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From: Webb City, MO...out in the garage

need some help with DTC's

i have a friend that called me the other night, wanting to know if i knew what was up with his '03 Tahoe. he said the driver information screen on the gauge cluster said something like "low engine output" if i remember. i told him to bring it over and i'd look at it since i've never heard of that. i hooked up my HP Tuners and this is what was in the DTC box:

Quote:

[TCM] U1199 - Loss of serial communications for class 2 devices (History) (Immature)
[TCM] U1255 - Class 2 Communication Malfunction (History) (Immature)
[TCM] C0300 - Rear Speed Sensor Malfunction (History) (Immature)
[TCM] C0305 - Front Speed Sensor Malfunction (History) (Immature)
[TCM] C0306 - (History) (Immature)
[TCM] C0327 - Encoder Circuit Malfunction (History) (Immature)
[TCM] C0374 - General System Malfunction (History) (Immature)
[TCM] C0379 - (History) (Immature)
[TCM] C0550 - ECU Malfunction (History) (Immature)
[TCM] B2725 - ATC Mode Switch Circuit Malfunction (History) (Immature)
[TCM] U1301 - Class 2 Short to Battery (History) (Immature)
[HVAC] B0434 - (History) (Immature)
[Convenience] B2355 - Driver Front Vertical Sensor Malf (History) (Immature)
[Convenience] B2375 - Driver Seat Asm Horiz Sensor CKT Malf (History) (Immature)
[Convenience] B1850 - Driver Lumbar Horiz Sensor CKT Malf (History) (Immature)
[Convenience] B1960 - (History) (Immature)

Continuous Tests
Misfire: Complete
Fuel System: Complete
Comprehensive Component: Complete

Once Per Trip Tests
Catalyst: Incomplete
Heated Catalyst: n/a
Evaporative System: Incomplete
Secondary Air System: n/a
A/C System Refrigerant: n/a
Oxygen Sensor: Incomplete
Oxygen Sensor Heater: Incomplete
EGR System: n/a

I tried clearing the codes and they all came right back. We have no idea what the problem is or could be, unless it just needs a new ECM and half a dozen other electonic parts

I didin't notice the "low engine ouput" message while he was at my house, and he said he hasn't seen it since but the Tahoe still kinda runs crappy, but does run and drive. I just figured i'd throw this up here and see if anyone had encountered this before or had any ideas as to the root of the problem.

Thanks

Jan 28, 2011 | 01:15 PM

Frost

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From: Richmond VA

[TCM] U1199 - Loss of serial communications for class 2 devices (History) (Immature)
[TCM] U1255 - Class 2 Communication Malfunction (History) (Immature)

These are from flashing/reading a cal most likely (though they could point to something physical).

The reason they come right back after a reset is that they are not being reset at all. The VCM-reset resets ECM codes, not codes from other modules such as the trans. Have him pull a battery cable for a minute or so and then re-connect. Drive it for a few miles and re-check the codes to see what has actually come back.

Jan 28, 2011 | 01:24 PM