Control module (ECM/PCM/BCM) failure on the 2004 Chevrolet Impala
When control module (ecm/pcm/bcm) failure gets reported
Owners of the 2004 Chevrolet Impala report control module (ECM/PCM/BCM) failure at a median of 70,000 miles. A quarter of the reports come in before 40,000 miles and a quarter after 100,000 miles, from 13 reports that carried an odometer reading.
A part like this is normally expected to survive 92,000 miles. It is the 21st most-reported problem on this model year.
The mileage distribution
The reported range runs from 30,000 miles at the tenth percentile to 120,000 miles at the ninetieth, a spread of 93,600 miles across the middle 80% of reports.
A spread this wide points at use rather than design. Towing, climate, service history and city mileage all move a failure like this, so the median is a weak guide to any individual car.
15% of the dated reports were filed under 36,000 miles.
The whole distribution
| 10th | 25th | Median | 75th | 90th |
|---|---|---|---|---|
| 28,000 miles | 42,000 miles | 71,800 miles | 100,000 miles | 121,600 miles |
Read the 10th percentile as “one report in ten arrived this early”. Exact figures are shown in this table because it is the table of record; everywhere else on the site they are rounded to the precision the sample can carry.
What a percentile can and cannot tell you here
These five numbers describe the readings owners gave, in order. The median is the middle one: half the reports arrived below it. The 10th and 90th are the edges of the bulk of the distribution, and the distance between them is the part worth reading. A tight spread — say 70,000 to 95,000 miles — points at something that wears out on a schedule, and the schedule is knowable. A wide one, 20,000 to 190,000, points at a fault that hits some cars and never troubles others, which means the mileage on the listing in front of you tells you very little about your odds.
What these figures are not is a survival curve. Every reading here comes from a car whose owner filed a complaint, so the sample contains only failures: it cannot say what share of the fleet made it past 150,000 miles untouched, because those owners had nothing to report. Nor is the mileage the moment of failure — it is the odometer reading as recalled at the time of filing, which may be weeks later and is sometimes rounded to the nearest ten thousand by the person typing it.
Percentiles are shown at all only once 8 readings exist for the vehicle and mode. Below that the middle of a handful of numbers is noise wearing a decimal point, so the figures are withheld rather than dressed up.
What happens, and what it costs
Putting it right typically runs $700–$3,000 at an independent US shop. That range is an editorial estimate held in this site's failure-mode catalogue, not a figure from NHTSA, and it is a repair cost rather than a diagnosis cost.
The same failure on other years
The same failure is reported on 13 model years of this car. It shows up earliest on the 2000, at a median of 35,000 miles, and latest on the 2008 at 125,000 miles.
By volume the 2002 carries the most reports, with 54; the 2004 has 15. A mode that appears across most years of a model is usually a design choice rather than a bad batch.
If one year stands out to the left, that is the year to avoid; if the whole line sits at a similar mileage, this is wear rather than a defect in one production run.
Tick median reported mileage Solid middle half of reports Faint 10th to 90th percentile Colour how bad the failure is when it happens
What owners wrote
Verbatim from NHTSA complaint narratives, trimmed for length. The mileage is the one the owner gave.
Dt: consumer complained about acceleration problems. The vehicle accelerated even though the foot was off the accelerator pedal. This happened 5 times in the past years. The accelerator only did this when the car was running for over 30 minutes. Previously, the engine could run for over 2 hours before this would happen. The car was in the shop 3 times, and the dealer had not been able to find the cause of the problem. Dealer performed a diagnostic test. But this did not lead to any information. They cruise control module was replaced after testing was done. The dealer suggested that consumer bring the car I when this problem occurred. Consumer contacted gm. They would document the claim and the vehicle 's history and that was all they could do. Consumer took the vehicle to 2 dealerships, and neither could find the cause of the problem.*ak
Speedometer acts erratically. Some kind of communication problem between the instrument cluster and the drivetrain control module. As many complaints I've seen, this should be a recall issue. *jb
2004 chevrolet impala - the headlights will go out without any warning while you are driving down the road. This is extremely dangerous! I am still in the process of trying to figure out how to get this problem corrected. I have already had the light sensor replaced and the BCM replaced. Neither of these corrected the problem. After many days and hours of research, I think it may be related to the multi-function switch on the steering column. This must become a recall as this endangers many lives! *tr
Also reported on the 2004 Chevrolet Impala
Instrument cluster or gauge failure
Other electrical problem
No-start or intermittent start failure
Ignition switch, key fob or immobilizer failure
Other engine problem
Other lighting problem
How far this goes
Complaints are voluntary, so 15 is a floor and not a count of affected cars. Mileages are typed in by owners and cluster on round numbers. And the mode itself is assigned by software reading the complaint text, which is reliable in bulk and fallible one report at a time.
Questions this page answers
At what mileage does control module (ecm/pcm/bcm) failure happen on the 2004 Chevrolet Impala?
Across 13 owner reports that included an odometer reading, half were filed by 70,000 miles. A quarter were filed before 40,000 miles and a quarter after 100,000 miles. These are the mileages owners reported when they complained, not a prediction for any individual car.
How common is control module (ecm/pcm/bcm) failure on the 2004 Chevrolet Impala?
15 reports have been filed with NHTSA, about 0.2 per 1,000 vehicles. Complaints are voluntary, so this is a floor rather than a count of affected cars.
What this is and is not. These are the mileages at which owners chose to complain to a federal agency, which is not the same as the mileage at which the part fails on every car. It skews toward failures that happened outside warranty, cost real money, or frightened someone. It is still the only public dataset that carries failure mileage at all, and the shape of a few hundred readings is informative even when a single one is not. Methodology · JSON · this failure on other cars
Source Owner complaints and recall records published by the US National Highway Traffic Safety Administration, model years 1996–2027 Figures rebuilt Published by AtWhatMileage How every figure is computed