Network code
U0100: Lost communication with engine computer
How much to fix U0100? Typically $170–$1,125.
Wide range: this job varies a lot. Itemize your quote for a better answer.
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $5 | $150 |
| Labor: 1.5 to 6 hours × $110 to $150 an hour | $165 | $900 |
| Fees: shop supplies, disposal, diagnostics | $0 | $60 |
| Total, rounded | $170 | $1,125 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in the US, $27.13 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, can bus wiring repair. Which repair your car needs depends on a proper diagnosis.
One of the car's modules cannot reach the engine computer (ECM or PCM) over the data network. The exact meaning varies by make, so check the scan tool or manual. Often the cause is power, ground or wiring, such as a weak battery, a blown fuse or a corroded plug, and not a failed computer.
- Safe to drive?
- Short trips only
- Most common cause
- Weak battery or bad ground
The car may stall, not start, or run rough. Stop if it stalls or loses power. Get it checked soon.
Get quotes from local shops
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What you may notice
- Check engine light on
- No-start or stalling
- Gauges not working
- Other warning lights
Common causes, most likely first
- Weak battery or bad ground
- Blown fuse or relay
- Damaged CAN bus wiring
- Corroded connector
- Failed engine computer
Check this first
Test the battery and check the engine computer fuses and relays. Many U codes come from low voltage or a bad ground.
Other repairs that sometimes fix U0100
| Repair | Typical range, US |
|---|---|
| ECU / engine control module replacement | $410 to $2,250 |
| Battery replacement | $150 to $470 |
| Diagnostic scan (check engine light) | $55 to $250 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Many states require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
U0100 questions
Is the computer bad?
Sometimes, but wiring and power faults are more common. A shop should check fuses, grounds and the battery before replacing a computer, since a new one can cost a lot and may not fix it.
Why many warning lights?
Modules depend on each other for data. When one drops off the network, others lose their input and set their own warnings, so many lights can come on at once even though one thing is wrong.
Can I clear it?
You can, but it may return if the cause is real. Clearing the code erases the record, not the fault, so use it only after the shop has fixed the problem.
How much does it cost to fix U0100?
The most common fix, can bus wiring repair, has a typical range of $170 to $1,125 across the US. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Typical range in 10 metro areas
Only the labor rate changes between cities. Same parts, same hours.
| Area | Typical range, estimate |
|---|---|
| Boston area, Massachusetts | $190 to $1,275 |
| New York City area | $180 to $1,200 |
| Los Angeles area, California | $180 to $1,250 |
| Chicago area, Illinois | $170 to $1,150 |
| Houston area, Texas | $160 to $1,100 |
| Dallas-Fort Worth area, Texas | $160 to $1,100 |
| Phoenix area, Arizona | $170 to $1,125 |
| Atlanta area, Georgia | $170 to $1,150 |
| Miami area, Florida | $160 to $1,125 |
| Seattle area, Washington | $190 to $1,250 |
Related codes
- U0073: Control module communication bus off
- U0121: Lost communication with ABS module
- P0A80: Hybrid battery weak or worn out
More network codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.