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Brake Pressure Modulator Valve (BPMV) Water Intrusion — Underhood Fire Risk
Underhood fire or smoke; electrical burning smell; unexplained vehicle fire while parked or operating
Catastrophic2021-2022
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GMC Sierra 2500HD diesel: Allison, DEF, and tailgate recalls. Repairs keep failing? CA lemon law may entitle you to a repurchase or replacement.
The GMC Sierra 2500/3500 HD with the 6.6L L5P Duramax diesel and Allison 10-speed transmission is the choice of serious work truck buyers — contractors, fleet operators, fifth-wheel towers — who cannot afford to be stranded. Yet owners of 2020-2022 model year trucks have lived through a string of federal safety recalls that cover the very systems they rely on most: the transmission that puts power to the ground, the brakes, and the tailgate that keeps cargo in the bed. On top of those recalls, diesel-specific problems — DEF system faults that throw the truck into limp mode, fuel injector connector failures misdiagnosed as much more expensive injector failures, and diesel particulate filter clogging — have sent owners to the dealer repeatedly without lasting resolution. If your Sierra HD Duramax has been back to the shop more than once for these issues and GM still hasn't made it right, California's lemon law may entitle you to a refund, a replacement truck, or civil damages.
The issues owners report most, ranked by severity — each one verified against a cited NHTSA source.
Underhood fire or smoke; electrical burning smell; unexplained vehicle fire while parked or operating
Harsh or abrupt downshifts; in rare cases rear wheels momentarily lock up while the truck is moving, especially downshifting from 8th gear; 'Reduced Propulsion' message and transmission stuck in 5th gear after TCM detects wear
Tailgate unlatches on its own while the truck is in Park or while driving; cargo falls out; tailgate opens unexpectedly after rain or wet conditions
Check engine light on; engine misfires (cylinders 1-8); rough or uneven engine performance; dealer diagnoses injector failure but injector replacement does not resolve the issue
'Service Emission System' warning on dashboard; 'DEF Level Low' alert even when tank is full; engine enters reduced-power limp mode; DEF tank connector overheating (DTCs P10D9, P143C, P10F3)
'Clean Exhaust Filter' or 'Service Exhaust Filter' message; DTC P2463; vehicle enters reduced-power limp mode; heavy black soot from exhaust; forced DPF regen required repeatedly
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.
Harsh or abrupt downshifts; in rare cases rear wheels momentarily lock up while the truck is moving, especially downshifting from 8th gear; 'Reduced Propulsion' message and transmission stuck in 5th gear after TCM detects wear
Safety recall affecting 135,323 Sierra HD trucks (2020-2022 diesel); momentary rear wheel lockup is a crash hazard. Software-only remedy leaves underlying mechanical defect unresolved. Repeated harsh shifting prior to 'Reduced Propulsion' mode constitutes substantial impairment of use and value. Multiple repair attempts may be required if valve hardware is not also replaced.
TCM software update per recall 24V797; worn valve hardware replacement covered under GM special service coverage; vehicles incorrectly repaired in December 2024 re-remedied under 26V083
Tailgate unlatches on its own while the truck is in Park or while driving; cargo falls out; tailgate opens unexpectedly after rain or wet conditions
194,266 GMC Sierra HD units covered (2020-2024); one of the largest unit counts of any HD truck recall. An open tailgate while driving creates a cargo-ejection and crash hazard. Owners who suffered cargo loss or a crash before the recall may have independent claims. Dealers may have closed 2024 MY trucks without full remedy until 24V894 expansion.
Dealer replaces exterior touchpad switch assemblies at no charge under recalls 24V060 and 24V894
Underhood fire or smoke; electrical burning smell; unexplained vehicle fire while parked or operating
Active park-outside advisory makes this vehicle unfit for normal use (garage parking) until repaired — a textbook impairment-of-use argument. 3,241 affected units is a narrow population; verify VIN eligibility. Fire risk qualifies as substantial safety defect.
Dealer replaces the BPMV assembly at no charge; GM issued 'park outside and away from structures' advisory until repair completed
Check engine light on; engine misfires (cylinders 1-8); rough or uneven engine performance; dealer diagnoses injector failure but injector replacement does not resolve the issue
Multiple repair visits common when dealers replace injectors before diagnosing the connector (connector fix is ~$50; injector replacement is thousands of dollars). Repeated failed repair attempts for engine misfires and MIL qualify under California lemon law nonconformity analysis. Document each repair order and DTC history.
Replace high-pressure fuel injector electrical connectors per TSB 23-NA-027; diagnosis of connector before injector replacement is required by GM
'Service Emission System' warning on dashboard; 'DEF Level Low' alert even when tank is full; engine enters reduced-power limp mode; DEF tank connector overheating (DTCs P10D9, P143C, P10F3)
Limp mode triggered by false DEF warnings substantially impairs use for commercial and towing applications — the primary use case for HD trucks. Repeated 'Service Emission System' warnings requiring dealer visits support nonconformity claims. The DEF tank connector arcing issue (~38,000 units) additionally creates a heat/electrical failure that may recur after software-only remedies.
Reductant Control Module software update per TSB 22-NA-150 (no charge); DEF tank harness connector reprogram per Service Update N212342980 for 2020-2021 units (~38,000 vehicles)
'Clean Exhaust Filter' or 'Service Exhaust Filter' message; DTC P2463; vehicle enters reduced-power limp mode; heavy black soot from exhaust; forced DPF regen required repeatedly
Repeated limp-mode events requiring dealer DPF forced-regen or replacement substantially impair the utility of a heavy-duty truck. Fleet operators and towing users are most vulnerable. P2463 prematurely on 2024 MY units (PIP5936 still under engineering review) may represent an unresolved defect warranting closer tracking.
Forced regeneration via GDS2 scan tool or extended highway drive cycle per TSB 10-06-05-002M; DPF replacement if regen fails; ECM calibration update if P2463 sets prematurely
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Vehicles repaired under recall 24V797 between December 2-8, 2024 received an incorrect TCM software calibration instead of the final production-ready calibration; these vehicles retain the transmission control valve wear risk and potential rear wheel lockup hazard.
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Same water-intrusion short circuit defect as 24V060: water contacts the electronic gate-release switch in the tailgate, causing inadvertent unlatching. This expansion campaign captures 2024 MY vehicles not fully addressed under the original 24V060 filing.
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Transmission control valve in Allison 10L1000 10-speed transmission is susceptible to excess wear over time, causing gradual loss of hydraulic pressure and harsh shifting. In rare cases, a downshift from 8th gear can produce momentary rear wheel lockup (less than 150 milliseconds).
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Water may intrude into the tailgate and contact the electronic power-unlatching gate-release switch, causing a short circuit that can result in the tailgate inadvertently unlatching while the vehicle is in Park.
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In vehicles where the electronic brake control module (EBCM) was replaced during assembly, bolts attaching the Brake Pressure Modulator Valve (BPMV) may not have been properly tightened, preventing proper sealing and allowing water intrusion into the BPMV.
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 gives new-vehicle owners powerful remedies when a manufacturer cannot repair a warranty defect after a reasonable number of attempts. If your Sierra HD Duramax has been back to the dealer repeatedly for the same issue — an Allison transmission that keeps going into limp mode, DEF system faults that return after reprogramming, or a tailgate that reopened after the recall repair — and the truck is still under GM's original factory warranty, you may be entitled to a full repurchase (return of your down payment, all monthly payments, and payoff of the remaining loan balance, minus only a mileage offset for miles driven before the first complaint) or a comparable replacement vehicle.
If GM knew about a defect — particularly one covered by an active recall — and delayed or failed to repair it in good faith, California law allows courts to impose a civil penalty of up to two times actual damages on top of the repurchase amount.
This is general legal information and not legal advice. The specific facts of your truck's repair history determine whether you qualify. Contact a California lemon-law attorney for a case-specific evaluation.
“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.
Intermittent problems on diesel HD trucks — a downshift shudder that disappears on the dealer's test drive, or DEF warnings that only appear after 50 miles of stop-and-go — are exactly the kind of defects dealers close as 'could not duplicate.' Do not accept that result as the end of the story. Here is how to build your case:
1. Film the symptom in real time. A ten-second phone video of the 'Reduced Propulsion' message or the tailgate hanging open while you're pulling away from a stoplight is evidence the dealer cannot dismiss. Date and location-stamp it if possible.
2. Note and document the exact conditions. Allison lockup-risk symptoms tend to occur on highway downshifts from 8th gear. DEF connector arcing tends to appear as limp-mode after city driving. DPF clogging is worse in vehicles used for short trips. Write these observations on the repair order when you drop the truck off.
3. Ask the dealer to reference recall 24V797 and TSB 22-NA-182 by number. If the transmission is shuddering or the truck is going into limp mode, these are the governing documents. Put the request in writing on your copy of the repair order.
4. Keep every repair order regardless of outcome. Under Song-Beverly, each dealer visit for the defect — including 'no fault found' visits — counts as a repair attempt. A pattern of multiple visits for transmission or DEF issues without resolution is strong evidence of an unrepairable nonconformity.
5. Request the completed warranty claim from each visit. This document, separate from the customer repair order, shows what GM was told and what they approved. It can reveal whether the right recall or TSB was even applied.
6. If the dealer replaces injectors for misfire codes that return, that itself is a pattern. TSB 23-NA-027 explicitly requires connector diagnosis before injector replacement. Repeated injector replacements that don't fix the misfire show the root cause was never properly addressed.
The Sierra 2500 HD diesel is a $70,000-plus work truck that many buyers depend on for their livelihood. An Allison transmission that locks up rear wheels — or, more likely, strands the truck in 5th-gear limp mode — does not just inconvenience the owner. It cancels jobs, breaks contracts, and costs real money every day the truck is out of service. The fact that recall 26V083 had to be issued in February 2026 because 1,055 trucks received the wrong TCM calibration during the original 24V797 remedy is not a minor administrative detail. It means some owners who thought their trucks were fixed in December 2024 are still driving trucks with the underlying defect. If you are one of them — or if your truck was never properly remedied — the clock on your lemon-law window is still running, and the pattern of failed repairs is exactly what the law is designed to address.
— The Margarian Law team
If your Sierra 2500 HD diesel has been in for Allison transmission problems, DEF system faults, a tailgate recall, or engine misfires — and the same issues keep coming back — your repair history may already tell a lemon-law story. California's Song-Beverly Act does not require you to keep going back forever. A free case evaluation takes minutes and costs nothing. Let an attorney review your repair orders and tell you whether GM owes you a replacement truck or a refund.
Yes. NHTSA recall 24V797 (issued October 2024) covers 135,323 GMC Sierra 2500/3500 HD trucks built for model years 2020-2022 with the 6.6L L5P Duramax diesel and Allison 10L1000 10-speed automatic transmission. The transmission control valve is susceptible to excess wear over time; in rare cases, a downshift from 8th gear can momentarily lock the rear wheels, increasing crash risk. The remedy is a TCM software update that detects valve wear and limits the truck to 5th gear ('Reduced Propulsion' mode) before a lockup can occur. Note: the software update does not replace the worn valve hardware, which is addressed separately under GM special service coverage. A second recall — 26V083 (issued February 2026) — covers 1,055 trucks that received an incorrect TCM calibration during the original repair window (December 2-8, 2024) and still carry the lockup risk.
It may be. Under recall 24V797, the updated TCM software is designed to detect excess wear in the Allison 10L1000 transmission control valve and proactively limit the truck to 5th-gear 'Reduced Propulsion' mode approximately 10,000 miles before a potential rear wheel lockup event. If your truck has entered this mode, it means the TCM has detected a problem — but the root-cause wear on the transmission control valve hardware may not yet have been addressed. The software update limits the hazard; the permanent fix is replacement of the worn valve, which is covered under GM special service coverage separate from the recall itself. If your truck keeps returning to 'Reduced Propulsion' mode after repeated dealer visits, that pattern of unresolved defects may qualify for California lemon-law relief.
This is a documented issue affecting 2020-2024 L5P Duramax Sierra HD trucks. General Motors issued Technical Service Bulletin 22-NA-150 to address a software anomaly in the Reductant Control Module that causes false 'Service Emission System' and 'DEF Level Low' warnings even when the DEF tank is adequately filled. The fix is a no-cost software update (reprogramming the K115 Reductant Control Module) at the dealer. On 2020-2021 trucks, a separate physical problem — the DEF tank harness connector overheating and arcing — can cause the same limp-mode symptoms along with DTCs P10D9, P143C, and P10F3. That issue (covered by GM Service Update N212342980) affected approximately 38,000 U.S. trucks. If your false DEF warnings or limp-mode events keep returning after dealer visits, that recurring pattern may support a lemon-law claim for an unrepairable nonconformity.
Yes, if your facts fit the statute. Under California's Song-Beverly Consumer Warranty Act, a vehicle that has a defect substantially impairing its use, value, or safety — and GM or an authorized dealer has been unable to repair it after a reasonable number of attempts within the warranty period — may entitle you to a full repurchase or a comparable replacement. The Sierra HD diesel has multiple confirmed safety recalls (Allison transmission lockup, tailgate, BPMV fire) plus documented TSB-covered defects that have required repeat dealer visits for many owners (DEF faults, injector connector failures, DPF clogging). Owners who have two or more repair visits for the same defect without a lasting fix, or whose trucks spent 30+ days at the dealer in a calendar year for warranty repairs, should speak with a California lemon-law attorney. A free case evaluation is the fastest way to know if your repair history meets the threshold.
This is a pattern documented in GM Technical Service Bulletin 23-NA-027. On 2020-2024 L5P Duramax trucks, the electrical connector pigtails on the high-pressure fuel injectors — especially cylinder 4 — can arc and fail, setting the same misfire DTCs (P0201-P0208 and P0300-P0308) that a failed injector would produce. The connector fix costs roughly $50 in parts; a replacement injector can cost thousands. GM's TSB explicitly requires technicians to diagnose the connector before authorizing injector replacement — but some dealers skip that step. If you've had injectors replaced once or more and the misfires keep returning, the connector was likely the root cause that was never addressed. Repeated failed repair attempts for the same misfire codes are exactly the kind of nonconformity pattern California's lemon law is designed to remedy.
There are two possible explanations. First, the remedy under recall 24V797 is a software-only TCM update that puts the truck into 5th-gear limp mode before a lockup can occur — it does not replace the worn transmission control valve hardware, which is addressed separately under GM special service coverage. If the hardware was not also replaced, the underlying wear continues. Second, if your truck's 24V797 repair was performed between December 2 and December 8, 2024, you may have received an incorrect TCM calibration. NHTSA recall 26V083 (issued February 2026) covers 1,055 trucks remedied during that specific six-day window — those trucks still carry the lockup hazard despite having gone through the recall process. Check your VIN at NHTSA.gov to see whether 26V083 applies to your truck, and return to the dealer for the corrected calibration at no charge.
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