Jeep Grand Cherokee 2026–2027 — warranty extension
Bulletin 66D Combo Rev1 · NHTSA communication 11036780 · issued Jul 27, 2026
Warranty extension
communication type
Engine
component
2026–2027
model years
4
vehicle entries
Official summary
CUSTOMER SATISFACTION NOTIFICATION NORTH AMERICA Spark Plugs Reference: 66D The spark plugs insulator on approximately 48,000 of the above vehicles may break due to excessive cylinder pressure. This pressure can cause the spark plug's ceramic insulator to crack, leading to a rough-running engine. If this issue is not resolved promptly, the broken fragments can fall into the cylinder and cause internal engine damage.
Vehicles covered
What a TSB means. Technical service bulletins are repair guidance manufacturers send to dealers — they are not recalls, and repairs are not automatically free (warranty extensions are an exception worth checking). The full document is available via NHTSA’s vehicle lookup.