GM bulletin PIC6663
What it saysThis PI communicates the possibility of a B1599 setting and directs to contact TCSC. NHTSA’s full summary ↓
GM filed this with NHTSA as a service bulletin dated Sep 18, 2026, received Sep 23, 2026. It names 4 model years across Chevrolet, GMC and Cadillac (2027). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
One page for every brand it was filed under. Each brand’s bulletins: Chevrolet · GMC · Cadillac.
Get the next GM bulletin for your model by email Weekly, only when something new is filed. Nothing else; one-click unsubscribe.
What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThis PI communicates the possibility of a B1599 setting and directs to contact TCSC.
Trouble codes it names: B1599
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| PIC6663 | Service bulletin | Sep 18, 2026 | 11037457 | PDF, 111 KB |
The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themChevrolet 2 model years
GMC 1 model year
Cadillac 1 model year
A vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
Email me new GM bulletins for one of these models
A weekly email, sent only in a week when GM files something new with NHTSA for the model you pick — service bulletins, campaigns, warranty extensions, over-the-air notices, every model year. Nothing else is sent; one-click unsubscribe in every message. Separate from recall alerts.
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for Chevrolet, GMC and Cadillac, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is GM PIC6663 a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the PIC6663 repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way.
Which vehicles does PIC6663 cover?
The manufacturer filed it against 4 model years across 3 brands (Chevrolet, GMC and Cadillac): 2027 Cadillac Lyriq, 2027 Chevrolet Suburban, 2027 Chevrolet Tahoe, 2027 GMC Yukon. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.