Chevrolet U1064 Code: Lost Communication With Body Control Module
Other modules stopped hearing the body control module on an older GM's Class 2 data line.
At a glance
Severity: Moderate
- Meaning
- Lost Communication With Body Control Module
- System
- Module Communication · Network
- Safe to drive?
- With caution
- Typical repair cost
- $5–$900
- DIY difficulty
- Moderate
On Chevrolets that use GM's Class 2 network, every module broadcasts a short 'I'm alive' message about every two seconds while the key is on. U1064 is set by the engine computer, cluster, radio or other modules when the body control module's message has been missing for around five seconds. The code is stored in the modules that noticed the silence, not in the BCM, and GM notes that a loss-of-communication code usually doesn't mean the module that stored it is faulty. It's common on 1999–2007 Silverado and Sierra, 2000–2006 Tahoe and Suburban, TrailBlazer, Impala and Cavalier, where the BCM sits under the driver's side dash and is exposed to water from cabin leaks. Depending on the model, a silent BCM affects lights, locks, chimes and the theft-deterrent check needed to start.
Can I keep driving? If the vehicle starts and the lights work, you can drive it to a shop with care. Check that headlights, brake lights and turn signals work before driving at night, and expect a possible no-start if the BCM also handles the security system.
How to read U1064
- U Network
- 1 Manufacturer-specific
- 0 Module Communication
- 64 Specific fault
Symptoms
- Interior lights, power locks or keyless entry stop working or act randomly
- Security light on and a crank-no-start or engine that dies after a second or two
- Door chimes, seat belt chime or key reminder silent
- Instrument cluster missing turn signal or high-beam indicators
- Several modules store U1064 at the same time
- Problems begin after heavy rain, washing or a leak into the driver's footwell
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Blown BCM fuse or poor BCM power/ground connection
- Water damage to the BCM or its connectors from a cowl, windshield or door leak
- Internal BCM failure
- Low battery voltage, a jump start or a battery that went flat
- Aftermarket remote start or alarm wired into BCM circuits
- Open or chafed Class 2 branch wire to the BCM
Diagnosis step by step
Scan and see who is talking
Scan all modules with a GM-capable tool. If every module except the BCM answers, focus on the BCM and its branch; if several modules are missing, treat it as a network fault (see U1000).
Tools: OBD-II scanner
Check battery and BCM fuses
Confirm the battery is healthy, then check every fuse that feeds the BCM; it usually has several battery and ignition feeds in both the underhood and interior fuse blocks. One blown feed can be enough to keep it silent.
Tools: Multimeter
Inspect the BCM and footwell for water
Remove the lower driver's side trim to reach the BCM. Wet carpet, water stains, white or green deposits on the connectors or a musty smell mean a leak has reached it; find and fix the leak as well as the module.
Tools: Flashlight, Screwdriver
Measure power, ground and the data line at the BCM
Back-probe the BCM connectors with the key on: each power pin should read battery voltage and grounds should be within a few tenths of a volt of zero. The Class 2 pin should show a changing voltage; if it's present at the diagnostic connector but not at the BCM, the branch wire is open.
Tools: Multimeter
Check aftermarket connections
Look for splices from remote starters or alarms near the BCM or steering column. Poor taps on BCM circuits can crash the module or back-feed its inputs.
Tools: Flashlight
Replace and set up the BCM if needed
A replacement BCM must be programmed for the vehicle's options with a GM-capable tool. On models with Passlock, a theft-system relearn is also needed so the engine will start.
Tools: OBD-II scanner
Where the parts are
- 1Battery
- 2Alternator
- 3Engine computer (ECM)
- 4CAN bus
- 5Transmission
- 6Wheel speed sensor
- 7High-voltage battery
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace blown fuse / clean BCM ground | Yes | $5–$120 |
| Fix water leak and dry/clean BCM connectors | No | $150–$500 |
| Repair Class 2 branch wire to BCM | No | $120–$350 |
| Replace BCM with programming and theft relearn | No | $350–$900 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Depends
U1064 itself doesn't always light the check engine light, so it may not fail an OBD emissions test on its own. If it sets engine codes with the light on, or the station can't read readiness data, the vehicle won't pass until it's repaired.
Frequently asked questions
Is U1064 the same as U0140?
They describe the same symptom, a silent body control module. U1064 is GM's older Class 2 numbering, and U0140 is the standard code used on CAN-based vehicles, including newer Chevrolets.
Why does my Chevy crank but not start with U1064?
On many GM vehicles of this era the BCM takes part in the Passlock theft check. If the engine computer doesn't get the right message from the BCM, it disables fuel and the security light comes on.
What is the Passlock relearn?
It's a procedure that teaches the engine computer to accept the body module again, commonly done by leaving the key in ON with the engine off until the security light goes out, which takes about ten minutes. The exact steps vary by model, so follow the service information.
Can I use a used BCM from a salvage yard?
Sometimes, but it carries the donor vehicle's settings and theft data. It generally needs reprogramming for your VIN and options, plus a theft relearn, before everything works correctly.
Sources
- Manufacturer public service information (cross-checked)
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