Johnsen's 4721 Mass Air Flow Sensor Cleaner
Priced as of May 16, 2026
4.6(695 ratings)Buy on AmazonSaved to your guest loadout. Sign up to also save to your Cabinet (consumables) or Kit (tools you own).
As an Amazon Associate and affiliate partner, CarCareTruth earns from qualifying purchases. Full disclosure
Prices may varyFrom the Safety Data Sheet
Full SDS ↗ (rev. 2017-06-20)GHS hazard codes are quoted from the manufacturer’s Safety Data Sheet. PPE tiers below translate those codes and the listed ingredient chemistry; they are not CarCareTruth recommendations.
EyesSituationalMfr. SDS §8SkinSituationalMfr. SDS §8 · 29 CFR 1910.1000 · GHS H361LungsRecommendedMfr. SDS §8 · 29 CFR 1910.134 · GHS H370Ventilation—No PPE in published sourcesShow details for all categories ▾Hide details ▴
From the manufacturer’s Safety Data Sheet, Section 8
“No H319 or H318 in SDS §2 mixture classification. Aerosol mist at face level during engine-bay work is the trigger — fine droplets can cause temporary irritation on direct contact.”
— Johnsen's
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
From the manufacturer’s Safety Data Sheet, Section 8
“No H315 or H317 in SDS §2 mixture classification. Brief incidental contact during typical MAF cleaning is the realistic scenario; the solvent load warrants care with repeated or extended skin contact.”
— Johnsen's
U.S. regulatory standard
29 CFR 1910.1000; 1910.1200
“Each employer shall assure that no employee is exposed [in excess of the PEL]…”
OSHA standards apply to workplaces. Cited here as the U.S. reference threshold for the underlying hazard class.
UN GHS hazard statement
H361“Suspected of damaging fertility or the unborn child”
UN GHS Rev. 9 (2021)
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
From the manufacturer’s Safety Data Sheet, Section 8
“DANGER signal word driven by H370 (organ damage, STOT SE 1) and H373 (STOT-RE Cat 2) at the §2 mixture level — petroleum distillate aerosol with genuine health-tier H-codes. The SDS identifies a health-based inhalation hazard, not a flammability-only DANGER. Use outdoors or with the garage door fully open.”
— Johnsen's
U.S. regulatory standard
29 CFR 1910.134; 1910.138; 1910.1000
“the primary objective shall be to prevent atmospheric contamination… When effective engineering controls are not feasible… appropriate respirators shall be used.”
OSHA standards apply to workplaces. Cited here as the U.S. reference threshold for the underlying hazard class.
CarCareTruth publishes the cited sources verbatim and does not advise what action a user should take. Consult the full SDS before use.
No PPE specified in published sources for ventilation. Absence does not imply “not needed” — consult the full Safety Data Sheet.
PPE tiers translate the manufacturer’s SDS and U.S. regulatory standards. Not professional safety advice. How we report safety.
CarCareTruth's Analysis
Last reviewed May 16, 2026
TL;DR Clears typical oil-mist MAF fouling and buyers report codes stayed cleared — including a direct comparison to the category's dominant brand with equivalent results. The DANGER signal word is driven by health H-codes (organ damage, repeated-exposure organ risk) at the §2 mixture level, not flammability alone. Use outdoors or with the garage door open; air-dry 3–5 minutes before reinstalling the sensor.
What it is and how it performs
Remove the MAF sensor, insert the straw, spray 2–4 short bursts, and air-dry 3–5 minutes before reinstalling. The formula evaporates quickly without visible residue per multiple verified-purchase reviews. Very high solvent load means one 10 oz can covers many cleaning sessions. Amazon evidence covers light-to-moderate oil-mist fouling; no before/after MAF voltage data from forums was found.
Who should buy this — and who should skip it
A practical choice for a home mechanic with a P0101/P0102 code and typical oil-mist fouling. Skip it if health profile matters: the DANGER classification reflects genuine health-tier chemistry and the SDS identifies a Prop 65 developmental toxicant. IPA-based formulas in the category score several points higher on health.
Safety and environmental impact
DANGER is driven by health H-codes at the §2 mixture level: organ damage (STOT SE 1) and repeated-exposure organ risk (STOT-RE Cat 2). The SDS §15 identifies a Prop 65 developmental toxicant in the ingredient list — the Amazon listing's false negative has been overridden. Respiratory protection is chemistry-warranted; eye protection and gloves are advisable. Air-dry 3–5 minutes before reconnecting the harness.
VOC content is 634 g/L (SDS §9). CARB compliance not stated. Naphtha carrier is not biodegradable. No aquatic toxicity codes in the §2 mixture classification.
From the manufacturer
Marketing copy from Johnsen's, via Amazon. Not editorial.
- •Package Dimensions: 6.604 cms (L) x 6.858 cms (W) x 6.604 cms (H)
- •Product Type: Auto Accessory
- •Package Quantity: 1
- •Country Of Origin: United States
Weekly pick
One product, one safety verdict, every week. No spam.
Manufacturer images
Manufacturer specifications
- Brand
- Johnsen's
- Item Weight
- 10 Ounces
- Product Dimensions
- 2.7"W x 2.6"H
- Global Trade Identification Number
- 00039101006147
- Manufacturer
- Johnsen's
- Brand Name
- Johnsen's
- UPC
- 039101006147
- Model Number
- 4721
- Manufacturer Part Number
- 4721
- Warranty Description
- check with manufacturer Regulararding warranty and support issues.
- Unit Count
- 10.0 Ounce
- Best Sellers Rank
- #721,887 in Automotive (See Top 100 in Automotive) #813 in Engine & Parts Fluid Cleaners #14,854 in Car Care
More in MAF Sensor Cleaner
CRC
Mass Air Flow Sensor Cleaner (11 oz aerosol)
CCT 5.8 · DecentHealth 3.4
Gumout
Professional Formula Mass Air Flow Sensor Cleaner
CCT 5.6 · DecentHealth 3.2
As an Amazon Associate and affiliate partner, CarCareTruth earns from qualifying purchases. Full disclosure
Community
0 postsShare how you use this product
Drop a quick comment or post a full review with photos and a star rating.
Sign in to postNew here? Create a free account.
Top Amazon review
↗External — Amazon's most-helpful review for context.
try this before buying parts
bought product in hopes of eliminating troublesome check engine light...cleaned contacts and works perfectly...exactly as described