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U0101 OBDII Code: No TCM Communication in 2009 Chevrolet Impala - Diagnosis & Fix Tips

Model: 2009 Impala Fault Code: U0101 Posted: 2016-10-30 20:30

Hi everyone! I recently scanned my 2009 Chevrolet Impala and found a U0101 diagnostic trouble code, which indicates 'lost communication with the Transmission Control Module (TCM)'. This means any active fault codes stored in the TCM are not being reported to the driver via the dashboard — making it difficult to diagnose underlying transmission issues. I'm concerned about potential damage from disconnecting modules or battery terminals, as improper 12V battery disconnection can disrupt RAP (Remote Access Programming) circuits and affect onboard systems like OnStar. Background: - Previously experienced severe shift problems with the GM 4T65E transmission. A dealer replaced gears and clutches two years ago but did not replace the transmission filter. - After replacing the filter myself on the 'DL' (dual-lube) version, shifting improved significantly — though not perfectly. - Research from Sonnax.com suggests that clogged or stuck valve bodies in the transmission are a common root cause. Dealerships often only replace easy-to-access components like gears and clutches without addressing these internal valves. Last year, I received a P1811 code ('low ratio / delayed shift') which I resolved successfully in October 2015 using a Trans-Go Shift Kit installed in the first and second gear shift accumulators, along with two bottles of Seafoam Trans Tune. Currently, I'm trying to confirm whether the U0101 code is active (not just in history or pending) and if there's any freeze frame data available. As of now, my scan tool reports no freeze frame information — this may limit troubleshooting options. Any advice on diagnosing or resolving the U0101 TCM communication issue would be greatly appreciated! Thanks in advance.

Related fault codes
U0101
Comments (2)
Anonymous 2016-10-31 11:20

Could you confirm if the Check Engine Light (CEL) is currently illuminated? Is the transmission functioning properly under normal driving conditions? Has the U0101 code been confirmed as active — not just in history or pending? Are there any freeze frame data points associated with this U0101 event? If so, what do they show?

Anonymous 2016-11-01 20:54

Thanks for the detailed response. Here's my current status: 1. Check Engine Light (CEL): Not illuminated — MIL light is off. 2. Transmission operation: Generally fine, but rough shifts can occur unexpectedly, especially during acceleration from a stop. 3. U0101 code status: Appears to be active currently; I'll verify again tonight using the scan tool. 4. Freeze frame data: Not available — my scan tool consistently reports 'no data' for this event. Previously, I had recurring issues with 1st-to-2nd gear shifts from a standstill. After identifying a P1811 code, I installed a Trans-Go Shift Kit in the first and second shift accumulators and added Seafoam Trans Tune. The issue improved noticeably — though not completely resolved. I also disconnected the battery for one hour as a troubleshooting step, which may have helped reset some internal circuits.