U0029: Vehicle communication network bus A performance fault
Communication bus A performance
Severity: Severity not verified — if the car runs badly, have it inspected
The code reports a degraded network bus rather than one failed part; what it means for driving depends on which other modules are affected.
It gets more serious if:
- Inspect soon: Inspect soon if U0029 comes with reduced power, steering assist loss, stalling or several lost-communication codes.
U0029 in short
U0029 means the vehicle network bus labeled A is not performing as expected, so modules may be missing or garbling messages. It is a network code, not a single failed part. A weak battery, bad ground or damaged wiring are common starting points. If power, steering or braking warnings appear with it, have it checked soon.
A modern vehicle has computers that trade messages over shared data buses. A "performance" code says the bus A messages were present but not behaving normally, rather than simply missing.
Two sources describe the code this way: a reference site lists U0029 as a bus A performance problem, and a 2018 Honda Accord owner wrote the readout as "vehicle communication bus A performance". Neither says which part failed.
GM preliminary information PIT5405B lists U0029 among many U-codes on 2014-2016 full-size trucks and SUVs with reduced power, blank displays or stalls, and points at a body control module ground at G218 and two connectors. That is a GM-specific finding and should not be assumed for other makes.
Most likely causes
Cause 1: Poor ground or power feed to a module on the bus
Supported by vehicle data- Why it ranks here
- GM PIT5405B ties a group of U-codes including U0029 to a trapped ground eyelet at G218 and loose terminals at X183 and X133 on 2014-2016 GM full-size trucks and SUVs; only the NHTSA summary was read.
- What would change this
- Rises if several modules lost communication together and the ground or connector shows damage. Falls if battery and grounds test good.
Cause 2: Damaged bus wiring, connector or an added device on the network
Common general cause- Why it ranks here
- A bus performance fault points at the shared network rather than one module; the reference sites do not name a specific part.
- What would change this
- Rises with recent wiring work, water damage or aftermarket electronics. Falls if the fault is steady and tied to one module.
Cause 3: A module on the bus transmitting bad data
Possible — needs testing- Why it ranks here
- One faulty module can disturb a whole bus, but no source in this file names a module for U0029.
- What would change this
- Rises if the code clears when one module is unplugged by a technician. Falls if the bus is fine with all modules connected.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read every module for stored codes and note which other lost-communication codes appear with U0029, and whether the code is current or history.
IfMany modules show lost-communication codes together
It meansSuspect a shared power, ground or network wiring fault.
IfU0029 is the only network code and is not current
It meansIt may have been a one-time disturbance such as a low battery event.
Step 2: Test the 12-volt battery and charging, check battery terminals, then ask a shop to inspect body control module grounds and harness connectors for corrosion, loose terminals or pinching.
Warning:Probing connectors or disconnecting modules can set more codes or damage electronics; on vehicles with airbag or high-voltage systems follow the service procedure before unplugging anything.
IfA ground or connector is damaged
It meansRepair it and retest the network.
IfPower and grounds are good but the bus still faults
It meansWiring-level network testing is needed.
Points to: Damaged bus wiring, connector or an added device on the network
Symptoms
- Warning lights or messages on several systems
- Reduced power or stall Gets more serious: stop and have it checked.
- Blank radio, cluster or climate display
How to fix
Step 1: Check that the battery terminals are clean and tight and the battery tests healthy.
Step 2: Ask a dealer whether a bulletin applies to your VIN.
Parts and cost context
- Body control module (BCM):GM PIT5405B points at the module ground and connectors, not the module itself; labor varies, get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
ChevroletYour car
2014–2016 · Silverado 1500
Supported by vehicle dataGM PIT5405B covers 2014-2016 Silverado 1500 with U0029 among many U-codes; the cause given is a body control module ground and two connectors. Whether it is still current is not verified.
PIT5405BStatus unverified
Reduced power, steering assist, stall or blank displays with multiple U-codes including U0029
2014–2016silverado-1500 · NHTSA 10083324
Check the body control module ground at G218 for a trapped insulator mat and inspect connectors X183 and X133 for loose or backed-out terminals. The same information lists GMC Sierra 1500, Yukon, Cadillac Escalade and Chevrolet Suburban and Tahoe.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
HondaYour car
2018 · Accord
Supported by vehicle dataA 2018 Accord owner reported the readout U0029-00 as vehicle communication bus A performance.
Related codes
U0029 questions
Is U0029 the same on every make?
Both sources read it as a bus A performance problem, but neither names a failed part, so what to repair depends on the vehicle and the other codes stored.
Sources and review
- U0029 generic definition
- GM PIT5405B: multiple U-codes with reduced power, steering assist or blank displays
- NHTSA complaint ODI 11442348: 2018 Honda Accord
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error