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Brake System Defect - Reduced Brake Assist or Unexpected Braking
brake pedal problem; reduced braking; unexpected braking; brake warning light
Safety2020
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5 NHTSA recalls on the 2020-2026 Cadillac CT4 — brakes, airbags, transmission. California lemon law may entitle you to a refund. Free case review.
You paid for a compact luxury sport sedan with Cadillac's name on the hood. The CT4 promised driving engagement on par with a BMW 3 Series, a cabin worthy of the price premium, and the peace of mind that a flagship American automaker stands behind its product. What some owners received instead was a sequence of escalating frustrations: a brake pedal that went hard and unresponsive on the highway, a transmission that lurched and banged under normal acceleration, an engine that leaked oil back onto the driveway after the dealer declared it fixed, and a cluster of warning lights — 'Service Driver Assist,' 'Steering Assist Reduced,' 'Service Brake System' — that appeared without warning and sometimes all at once.
The 2020-2026 Cadillac CT4 was built on GM's Alpha platform in Lansing, Michigan, and offered two principal powertrains: the 2.0L turbocharged LSY four-cylinder in base trims and a twin-turbocharged 3.6L LF4 V6 in the high-performance CT4-V Blackwing. Five separate NHTSA recall campaigns — covering the brake boost system, both roof-rail airbag systems, daytime running lights, and the 10-speed automatic transmission — have touched the CT4 across its production run. Several GM-issued technical service bulletins document additional defects: cam carrier gasket oil leaks, EVAP purge pump failures covered under special programs lasting 15 years and 150,000 miles, and a camera module reset loop that disables Super Cruise and automatic emergency braking.
These are not one-off bad-luck stories. They are documented, manufacturer-acknowledged defects with published service bulletins and recall campaigns. If your CT4 has spent multiple days at the dealer for any of these conditions, California's Song-Beverly Consumer Warranty Act gives you rights that your dealer may not volunteer.
The issues owners report most, ranked by severity — each one verified against a cited NHTSA source.
brake pedal problem; reduced braking; unexpected braking; brake warning light
airbag warning light; passenger airbag may not deploy; SRS warning; occupant detection fault
airbag warning light; passenger airbag may not deploy; SRS warning; occupant detection fault
tail light out; exterior light warning; reduced rear visibility
transmission shifts unexpectedly; hesitation; harsh shift; transmission warning
harsh or lurching downshift at highway speed; loud bang or clunk from transmission under light acceleration; ABS event warning on DIC; 'D' indicator flashing; front wheels momentarily lock; vehicle feels like it hits a wall when downshifting from 8th gear; check engine light; P2812 or P2814 fault codes
A settled Margarian Law case on this exact model, published with the actual settlement math.
Open any defect for the symptoms and why it matters for a California lemon-law claim. Each is tied to a cited NHTSA source.
brake pedal problem; reduced braking; unexpected braking; brake warning light
NHTSA recall 20V588 covers sensor contamination in the electronic brake boost module causing loss of brake assist — a direct brake-failure safety defect. Under Cal. Civ. Code §1793.2, GM must repair a safety-recall defect within a reasonable number of attempts. If the dealer has performed the recall remedy but brake-related warnings or performance issues persist, the owner may have a Song-Beverly claim for failure to conform to warranty. The 2020 CT4's first model year adds weight to a 'design defect present at delivery' argument.
GM will notify owners, and dealers will replace the electronic brake boost module, free of charge. The recall began December 9, 2020. Owners may contact Chevrolet customer service at 1-800-630-2438, Cadillac customer service at 1-800-333-4223, or Buick customer service at 1-800-521-7300. GM's number
airbag warning light; passenger airbag may not deploy; SRS warning; occupant detection fault
NHTSA recall 21V421 addresses a gateway module software flaw that causes the airbag malfunction indicator to illuminate inconsistently, masking true airbag system faults. An erratic safety-system warning light on a vehicle under warranty constitutes a defect requiring cure. If the dealer performs the software update but the warning light returns — or if a related SRS fault is discovered — the owner has grounds for a Song-Beverly claim based on failure to permanently repair a safety-system defect.
The communications gateway module software will be updated by a dealer, or through an over-the-air (OTA) update, free of charge. Owner notification letters were mailed on July 1, 2021. Owners may contact Buick customer service at 1-800-521-7300, Cadillac customer service at 1-800-458-8006, Chevrolet
airbag warning light; passenger airbag may not deploy; SRS warning; occupant detection fault
NHTSA recall 21V611 documents that roof rail side-curtain airbags were twisted during installation at the factory, risking non-deployment in a crash. GM confirmed the defect after NHTSA observed improper airbag deployment in a crash test on a 2020 CT5. This is a manufacturing-origin safety defect: if the dealer inspection under 21V611 does not resolve the owner's SRS concerns, or if subsequent airbag warning lights appear, Song-Beverly's safety-defect repair provisions are squarely implicated.
Dealers will inspect both left and right-side roof rail air bags and reinstall the air bags, as necessary, free of charge. Owner notification letters were mailed on August 30, 2021. Owners may contact Cadillac customer service at 1-800-458-8006. GM's number for this recall is N212342780.
tail light out; exterior light warning; reduced rear visibility
NHTSA recall 22V903 addresses daytime running lights that fail to deactivate when headlights are on, creating glare for oncoming drivers. Although a software OTA remedy was available, if the dealer fails to apply the update or the DRL condition recurs post-update, the owner has a warranty-repair failure argument under Song-Beverly. A lighting defect in a vehicle marketed on safety technology is also relevant to the vehicle's represented value.
The body control module software will be updated by a dealer, or through an over-the-air (OTA) update, free of charge. Owner notification letters were mailed January 23, 2023. Owners may contact GMC customer service at 1-888-988-7267, Chevrolet customer service at 1-800-222-1020, or Cadillac custome
transmission shifts unexpectedly; hesitation; harsh shift; transmission warning
NHTSA recall 25V148 confirms that the 10L80 transmission control valve can wear to the point of causing momentary wheel lock-up at speed — a non-collision crash risk. Owner-reported transmission harshness and ABS events (aligned with TSB 21-NA-275) predate the recall by years, meaning some owners endured multiple failed repair attempts before the recall was issued. Under Song-Beverly, that repair history counts: two or more dealer visits for transmission harshness/wheel lock-up, or 30+ cumulative days out of service, may qualify the vehicle for replacement or refund regardless of whether the recall remedy has since been applied.
Dealers will install transmission control module monitoring software, free of charge. Owner notification letters were mailed April 7, 2025. Owners may contact Cadillac customer service at 1-800-333-4223 or Chevrolet customer service at 1-800-222-1020. GM's number for this recall is N242480630.
harsh or lurching downshift at highway speed; loud bang or clunk from transmission under light acceleration; ABS event warning on DIC; 'D' indicator flashing; front wheels momentarily lock; vehicle feels like it hits a wall when downshifting from 8th gear; check engine light; P2812 or P2814 fault codes
Wheel lock-up at highway speed is a loss-of-vehicle-control safety defect. Under Song-Beverly (Cal. Civ. Code §1793.2), if the dealer has attempted to repair this condition two or more times without a permanent fix — or the vehicle has been out of service for 30+ cumulative days for related powertrain/transmission work — the owner may qualify for a replacement or refund. The TSB-to-recall trajectory shows GM was aware of the defect before issuing the recall, strengthening a lemon-law timeline argument.
Recall 25V148: TCM software update to detect valve wear ~10,000 miles before lock-up risk; if wear confirmed, transmission limited to 5th gear maximum with MIL until valve body replaced. TSB 21-NA-275 (pre-recall): direct valve body replacement.
oil drips on garage floor under engine bay; burning oil smell from engine; low oil level warning on DIC; visible oil seepage near cam carrier cover or front of engine; oil film on transmission bellhousing or undercarriage; repeat leaks after dealer repair
A recurring engine oil leak constitutes a substantial impairment of the vehicle's use and value. If the dealer has repaired this defect two or more times without success, or the vehicle has been out of service for 30+ cumulative days for related engine work, the owner may have a Song-Beverly claim. GM's issuance of TSB 21-NA-240 confirms manufacturer awareness, supporting a reasonable repair attempt obligation argument.
GM TSB 21-NA-240 directs use of UV fluorescent dye to pinpoint the leak, followed by resealing the cam carrier gasket T-joint with updated sealant specification and torque values. Repeat visits are common if dealer performs partial reseal only.
'Service Driver Assist' message at startup; 'Take Steering' alert mid-highway; Super Cruise unavailable or drops out unexpectedly; automatic emergency braking disabled; lane keep assist not functioning; DTC U1614/U1615/U1616 stored; warning reappears after each restart; adaptive cruise control disengages without input
Inoperative automatic emergency braking and lane-keep assist constitute safety system failures. Under Song-Beverly, a vehicle with a repeatedly non-functional safety feature is substantially impaired. Two or more failed repair attempts for this issue, or 30+ days out of service, can trigger lemon-law eligibility — particularly where the ADAS package was a material purchase incentive for the buyer.
Diagnose with GDS2 for DTCs U1614/U1615/U1616. Some vehicles require front view camera reprogramming (service update N202305180) first. If IPM is confirmed as root cause, replace the Image Processing Module.
check engine light illuminated; DTC P1467 (EVAP Purge Pump Underspeed) or related P146x codes; failed emissions test/smog check; fuel vapor odor in some cases; no driveability impact in early stages but MIL remains on
A persistent check engine light that returns after dealer repair represents a recurring defect under Song-Beverly. If the dealer fails to resolve the EVAP code within a reasonable number of attempts, or the vehicle is out of service 30+ cumulative days across multiple visits, the owner may have a qualifying lemon-law claim regardless of the functional severity.
Replace EVAP purge pump assembly at no charge under GM Special Coverage N232395310 (2020-2021 CT4, 15 years/150,000 mi) or N242484740/N242441120 (2022-2023 CT4, same coverage terms). Repair performed by authorized Cadillac dealer.
brake pedal suddenly hard and unresponsive; 'Steering Assist Reduced' warning; 'Service Brake System' message; multiple DTC codes simultaneously (power steering, brake, engine communication faults); vehicle enters limp mode at highway speed; power steering lost with wheel very difficult to turn; incident repeats after dealer finds nothing wrong
Simultaneous brake and steering failure at highway speed is among the most serious safety impairments recognized under Song-Beverly. If this condition has recurred on the same vehicle after repair, or the dealer has failed to duplicate and refused to document the complaint, the owner has strong grounds for a lemon-law claim — particularly because recall 20V588 only partially addressed the brake boost system and owners report the broader failure pattern persists.
Dealers typically reprogram the brake boost module (per 20V588 remedy) or replace individual failing modules; however, NHTSA complaint data shows recurrence after repair. Owners should insist on documentation of all warning codes even when symptoms cannot be immediately duplicated.
center infotainment screen goes black on startup; screen freezes mid-drive; navigation, Apple CarPlay, or Android Auto unresponsive; instrument cluster DIC blank or slow to initialize; screen requires hard reset (hold power button); problem returns after restart; audio system silent with black screen
While an infotainment failure alone may not constitute a Song-Beverly 'substantial impairment,' a screen that is blank or frozen compromises backup camera visibility (a federal safety requirement on post-2019 vehicles) and renders navigation and communications unavailable. Multiple failed repair attempts for this condition, especially when combined with other CT4 defects, can contribute to a lemon-law claim under California's cumulative-defect standard.
Dealer-applied infotainment software update or radio module reprogramming. In persistent cases, radio/HMI module replacement. OTA updates have resolved some instances without dealer visit.
remedy available
General Motors LLC (GM) is recalling certain 2019-2020 Cadillac CT6, 2020-2021 CT4, CT5, and 2020-2022 Chevrolet Camaro vehicles equipped with a 10-speed transmission. The transmission may become damaged internally and cause the wheels to lock-up.
remedy available
General Motors, LLC (GM) is recalling certain 2020-2023 Cadillac CT4 and CT5; 2021-2023 Buick Envision; and 2022-2023 Cadillac Escalade and Escalade ESV, Chevrolet Silverado 1500, Suburban, Tahoe, GMC Sierra 1500, Yukon, and Yukon XL vehicles. The daytime running lights (DRLs) may not deactivate when the headlights are on. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 108, "Lamps, Reflective Devices, and Associated Equipment."
remedy available
General Motors, LLC. (GM) is recalling certain 2020-2022 Cadillac CT4 and CT5 vehicles. The roof rail side-curtain air bags may not have been installed correctly, which could result in an improper air bag deployment during a crash.
remedy available
General Motors, LLC (GM) is recalling certain 2021 Buick Envision, Cadillac CT4, CT5, Escalade, Escalade ESV, Chevrolet Tahoe, Corvette, Suburban, GMC Yukon, Yukon XL vehicles. The communications gateway module incorrectly processes a loss of communication with the sensing diagnostic module (SDM), causing the air bag malfunction indicator light to inconsistently illuminate.
remedy available
General Motors LLC (GM) is recalling certain 2020 Chevrolet Corvette and Cadillac CT4, CT5 and XT4, 2021 Chevrolet Trailblazer, and 2020-2021 Buick Encore GX vehicles. Sensor connection contamination in the electronic brake boost system may cause an interruption of communication between the sensor and the brake boost system.
Every item below comes from this vehicle's documented defects. The more you recognize, the more a free case review is worth your time.
California's Song-Beverly Consumer Warranty Act (Cal. Civ. Code §1790 et seq.) is one of the strongest lemon-law statutes in the United States. Here is how it applies specifically to the Cadillac CT4:
Repair attempts: If the manufacturer or its authorized dealer (Cadillac) has made two or more unsuccessful repair attempts for a defect that is likely to cause death or serious bodily injury — such as brake boost failure (20V588), wheel lock-up at speed (25V148), or inoperative automatic emergency braking (TSB 20-NA-178) — a lemon-law presumption may arise after just two attempts. For non-safety defects like the cam carrier oil leak or EVAP pump failure, four repair attempts may be needed before the presumption applies.
Out-of-service days: If your CT4 has been in the shop for warranty repairs for a total of 30 or more calendar days (they do not need to be consecutive), you may qualify for a replacement or refund regardless of the number of repair attempts. This is particularly relevant for CT4 owners whose cars have been held for recall parts or extended diagnostics.
What you may be entitled to: Under Song-Beverly, a qualifying owner may be entitled to a replacement vehicle of comparable value, a full refund of the purchase price (including taxes, registration, and finance charges), or a civil penalty of up to two times the purchase price if the manufacturer's refusal to repurchase was willful. Attorney's fees are recoverable, meaning a qualified lemon-law attorney typically handles these cases at no upfront cost to you.
Important note: This information describes California law as of June 2026 and is provided for general informational purposes only. It does not constitute legal advice and does not create an attorney-client relationship. The specific facts of your situation — including repair order dates, mileages, and defect descriptions — determine whether you have a viable claim. Consult a qualified attorney to evaluate your individual circumstances.
“Could not duplicate” doesn't mean the defect isn't real. Here's exactly what to do to protect a potential California lemon-law claim.
Document the moment it happens. Photos, video, and screenshots of any warning lights — with the date and the mileage.
Get a repair order every visit — even “found nothing.” That paperwork is the foundation of a claim.
Check your VIN at nhtsa.gov/recalls. Note any recall that has no available remedy yet.
Track your out-of-service days. California law counts the cumulative days your vehicle spends in the shop.
Keep loaner & rental records. Alternate-transport paperwork during long repairs matters.
Save everything in one place. Symptoms, dates, repair orders, and every repeat visit — the intermittent ones especially.
Cadillac CT4 defects — particularly the brake/steering multi-failure, transmission harsh shift, and ADAS dropout — are notoriously intermittent. Dealers frequently return the car with 'unable to duplicate' on the repair order. Here is how to protect your legal rights:
1. Document every event immediately. Note the exact date, mileage, road conditions, speed, gear position, and every warning message that appeared. Photograph the dashboard if it is safe to do so. Time-stamped photos from a smartphone are admissible evidence.
2. Request a repair order for every visit — even when the dealer says it cannot duplicate. Under California law, each repair attempt must be documented. A repair order that says 'could not duplicate, no defect found' still counts as a repair attempt. Do not accept a verbal assurance with no paperwork.
3. Specifically request that the dealer check for stored fault codes. DTCs P2812 or P2814 (transmission valve), U1614/U1615/U1616 (ADAS module), P1467 (EVAP pump), and brake-related communication codes may be present even when symptoms are not active. Ask that all stored and pending codes be listed on the repair order.
4. Ask the service writer to document 'customer states vehicle experienced [symptom] on [date] at [mileage]' even when the technician cannot reproduce the issue. This language creates a written record linking your symptom to the service visit.
5. Track cumulative out-of-service days. California's Song-Beverly Act presumes a vehicle is a lemon if it has been out of service for 30 or more cumulative calendar days for warranty repairs, or if the same defect has required repair four or more times. Keep a running log. Include pre-appointment waiting time if the dealer kept the car.
6. If the dealer performs the 20V588 or 25V148 recall remedy and the same symptom returns, that is a second repair attempt for the same defect — even though it was framed as a recall. California courts have held that recall repairs count toward the Song-Beverly repair-attempt tally.
7. Escalate to Cadillac Customer Assistance and document the case number. A manufacturer-level case number shows the manufacturer was notified directly and had an opportunity to cure — a prerequisite GM will look for before any buyback discussion.
The Cadillac CT4's recall record is notable not just for the number of campaigns — five in six model years — but for what they cover: brake failure, airbag non-deployment risk, and transmission wheel lock-up. These are not cosmetic issues. They are the kind of defects that regulators and courts take seriously.
What concerns us more than the recalls themselves is the pattern in NHTSA complaint data: owners reporting simultaneous brake and steering failure that the dealer repeatedly cannot duplicate, transmission harshness that predates the 2025 recall by years, and ADAS systems that disable themselves without warning. The gap between when owners started filing complaints and when GM issued recalls or service bulletins is, in multiple instances, measured in years.
If your CT4 has spent significant time at the dealer for any of these conditions, an evaluation of your lemon-law rights costs you nothing and may be worth considerably more.
— The Margarian Law team
If your Cadillac CT4 has been to the dealer two or more times for brake failure, transmission issues, airbag warnings, or recurring check engine lights — or if your car has been out of service for 30 or more days — you may have options under California's lemon law. Margarian Law has represented thousands of California vehicle owners and offers a free case review with no upfront cost to you. Call us or submit your repair orders online to find out if your CT4 qualifies.
Yes. In March 2025, NHTSA issued recall 25V148 covering 2020-2021 Cadillac CT4 models with the 10-speed automatic transmission. A worn transmission control valve can cause momentary front-wheel lock-up during a downshift, posing a crash risk. The initial remedy is a software update that detects valve wear; if wear is confirmed, the valve body must be replaced. If your CT4 has experienced harsh shifts, a loud bang, or an ABS warning during acceleration, contact your Cadillac dealer immediately to schedule the recall repair.
A GM Technical Service Bulletin (TSB 20-NA-178) addresses exactly this symptom on 2020-2021 CT4 models equipped with the ADAS camera package. The Image Processing Module can enter a reset loop at power-up, setting fault codes U1614/U1615/U1616 and disabling Super Cruise, automatic emergency braking, and lane keep assist. Dealers can diagnose this with GM's GDS2 scan tool; the fix typically involves reprogramming or replacing the Image Processing Module. If the warning returns after a dealer visit, that is a second documented repair attempt — relevant to a California lemon-law evaluation.
Yes, in part. NHTSA recall 20V588 covers 2020 Cadillac CT4 vehicles for a sensor contamination defect in the electronic brake boost system that can cause complete loss of power brake assist. When assist is lost, the pedal becomes very hard and significantly more force is required to stop. NHTSA complaint data also documents a broader pattern of simultaneous brake and power steering failure on 2020-2022 CT4s that may not be fully resolved by the 20V588 recall remedy alone. If your CT4 has experienced brake or steering issues — even after the recall repair — document every visit and consult a lemon-law attorney.
DTC P1467 indicates an EVAP purge pump underspeed fault — a known defect GM has acknowledged with two special coverage programs. N232395310 covers 2020-2021 CT4 models for 15 years or 150,000 miles; N242484740/N242441120 extends the same coverage to 2022-2023 CT4s. Take your vehicle to a Cadillac dealer and reference the applicable program number. GM will replace the EVAP purge pump at no charge under either program. A persistent check engine light that prevents a California smog check can also block vehicle registration renewal — an impairment of use that is relevant to a lemon-law claim if the problem recurs after repair.
Yes. GM TSB 21-NA-240 specifically addresses engine oil leaks from the cam carrier gasket T-joint on 2020-2025 CT4 models with the 2.0L Turbo (LSY) engine. The root cause is insufficient sealant applied during manufacturing; oil can appear to originate from the camshaft area, front engine cover, or oil pan. The TSB directs dealers to use UV dye to locate the exact leak path before resealing. Repeat leaks are reported when dealers perform a partial reseal. If your CT4 has returned to the dealer two or more times for engine oil leaks and the problem persists, you may have grounds for a California lemon-law claim.
California's Song-Beverly Act does not set a fixed number that applies to every case, but it creates legal presumptions: two repair attempts for a defect likely to cause death or serious injury (e.g., brake failure, wheel lock-up, airbag non-deployment) or four attempts for other substantial defects may qualify your vehicle. Additionally, 30 or more cumulative out-of-service days for warranty repairs — regardless of the number of visits — is a separate qualifying path. Recall repairs count as repair attempts. A qualified lemon-law attorney can review your repair orders at no cost to determine whether your specific CT4 repair history meets the threshold.
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