2026 ICD-10-CM Diagnosis Code T58.01XAToxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional), initial encounter

ICD-10-CM Codes›S00–T88›T51-T65›T58

ICD-10-CM T58.01XA
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T58.01XA is a billable ICD-10-CM diagnosis code for toxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional), initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 917 through 918. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, accidental/unintentional; External cause codes: poisoning by non-drug; and Toxic effects, initial encounter.

Code Identity

ICD-10-CM Code
T58.01XA
Billable Status
Yes — Valid for Submission
Code Describes
Toxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional), initial encounter
Short Description
Toxic effect of carb monx from mtr veh exhaust, acc, init
Parent Code
T58.01
Toxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional)

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT51-T65Toxic effects of substances chiefly nonmedicinal as to source
CategoryT58Toxic effect of carbon monoxide
This CodeT58.01XAToxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional), initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Accidental poisoning by exhaust gas from gas engine
  • Accidental poisoning by exhaust gas from motor pump
  • Accidental poisoning by exhaust gas from stationary farm tractor
  • Accidental poisoning by exhaust gas from stationary motor vehicle
  • Accidental poisoning by motor vehicle exhaust gas
  • Carbon monoxide poisoning from motor vehicle exhaust
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion, driver of motor vehicle injured
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion, motor cyclist injured
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion, occupant of tram injured
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion, passenger of motor vehicle injured
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion, passenger on motor cycle injured
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion, pedal cyclist injured
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion, pedestrian injured
  • Noncollision motor vehicle traffic accident involving accidental poisoning from exhaust gas generated by motor vehicle while in motion, rider of animal or occupant of animal-drawn vehicle injured
  • Poisoning by carbon monoxide from aircraft while in transit, without accident to aircraft
  • Poisoning by carbon monoxide from aircraft while in transit, without accident to aircraft, member of crew of commercial aircraft in surface to surface transport injured
  • Poisoning by carbon monoxide from aircraft while in transit, without accident to aircraft, occupant of commercial aircraft in surface to air transport injured
  • Poisoning by carbon monoxide from aircraft while in transit, without accident to aircraft, occupant of military aircraft injured
  • Poisoning by carbon monoxide from aircraft while in transit, without accident to aircraft, parachutist injured
  • Poisoning by exhaust gas in aircraft
  • Poisoning by exhaust gases on board watercraft

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Toxic effect of carbon monoxide (T58). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR EXT020
External cause codes: intent of injury, accidental/unintentional
Default principal diagnosis: inpatient No · outpatient No
CCSR EXT015
External cause codes: poisoning by non-drug
Default principal diagnosis: inpatient No · outpatient No
CCSR INJ023
Toxic effects, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Table of Drugs and ChemicalsClinical

Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.

SubstanceAccidentalSelf-harmAssaultUndeter­minedAdverse
Effect		Under­dosing
Exhaust gas (engine) (motor vehicle)T58.01T58.02T58.03T58.04––
Motor exhaust gasT58.01T58.02T58.03T58.04––

Patient EducationClinical

Carbon Monoxide Poisoning

Carbon monoxide (CO) is a gas that has no odor or color. But it is very dangerous. It can cause sudden illness and death. CO is found in combustion fumes, such as those made by cars and trucks, lanterns, stoves, gas ranges and heating systems. CO from these fumes can build up in places that don't have a good flow of fresh air.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T58.01XA to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
986 Tox eff carbon monoxide
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
E868.2 Acc poison-exhaust gas
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About T58.01XAOverview

Is T58.01XA a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional), initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character A in T58.01XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional), such as an emergency visit or first evaluation.

What MS-DRG does T58.01XA group to?

When toxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional), initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, with relative weights from 0.8571 to 1.5684 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of T58.01XA?

Under the General Equivalence Mappings, toxic effect of carbon monoxide from motor vehicle exhaust, accidental (unintentional), initial encounter converts to ICD-9-CM 986 (tox eff carbon monoxide) and E868.2 (acc poison-exhaust gas). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.