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Service bulletin 18-027-21

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id10190692
Published by NHTSA2021-04-26
Manufacturer's number18-027-21
Manufacturer's date2021-03-06
NHTSA componentPOWER TRAIN

NHTSA's summary

Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the PCM with the latest available software. The customer may notice the following condition:The oil change interval is too short. The oil change message shows up at around 12,000 km / 7,456 mi or earlier and the normal oil change interval is 12 months or 20,000 km / 12,427 mi.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Transmission and driveline

Vehicles listed
JEEP GRAND CHEROKEE2021

Listing a model year does not mean every vehicle of it is concerned: the document says which.

Other bulletins for the same vehicles and component
S26210000042026-10-07. Service bulletin. The Customer May Complain About a Popping Noise, Grinding Noise, or an Intermittent No Reverse or Forward Transmission Engagement. The Tech May Find Damaged and/or Worn Transmission Output Shaft Splines (850RE Transmission Only)
1135282026-07-23. Service bulletin. SHAFT - AXLE HALF
1135292026-07-23. Service bulletin. SHAFT - AXLE HALF
18-050-262026-04-22. Service bulletin. Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must SYMPTOM: exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): ● P0300 - Multiple Cylinder Misfire - In Active or Stored status set during cold start catalyst heating. ● P0301 - Cylinder 1 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0302 - Cylinder 2 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0303 - Cylinder 3 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0304 - Cylinder 4 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0305 - Cylinder 5 Misfire - In Active or Stored status set during cold start catalyst heating. ● P0306 - Cylinder 6 Misfire - In Active or Stored status set during cold start catalyst heating. Customers may also comment on one or more of the following: ● Check engine illuminates when fueling the vehicle while the engine is running. ● Vehicle has a noticeable misfire. ● Vehicle idles rough. ● Engine noise. NOTE: Noise is heard coming from the valvetrain. In addition, the following software enhancement is available: ● Update to prevent customers from driving their vehicles while the Electric Park Brake (EPB) is engaged. Engine torque will be limited to prevent the Rear Drive Unit from being damaged. NOTE: Previously, the EPB would remain engaged without any torque limit which could lead to the Rear Drive Unit being damaged/broken. This bulletin involves reprogramming the PCM with the latest available software.
S26230000232026-04-15. Service bulletin. Power Liftgate Inoperative.
S2621000003 REV.A2026-03-18. Service bulletin. The vehicle will exhibit a service transmission/check engine warning indicator for the following transmission models: 845RE, 8HP45, 850RE, 8HP50, 8HP70, 8HP75, 8HP75-PHEV, 8HP75-LCV, 8HP90, 8HP95. Transmissions may exhibit the following diagnostic codes: P07E4, P1DB2, P0716, P1B14, P0733, P1D90, P1DB7, P1B13.
S26210000032026-03-05. Service bulletin. Service transmission/check engine warning indicator for the 850RE, 8HP50, 8HP70, 8HP75, 8HP75-PHEV transmissions that have fault codes P07E4, P1DB2, P0716, P1B14, P0733, P1D90, P1DB7, P1B13.
S2521000004 REV.B2026-01-21. Service bulletin. The customer is experiencing a clicking or pop noise from the steering knuckle and bearing area during turns while driving.
1091612025-12-23. Service bulletin. SWITCH - TRANSFER CASE, RIDE HEIGHT, TERRAIN SELECT
S25210000052025-12-23. Service bulletin. The customer states the ABS and Traction Control warning comes on. Vehicle sets wheel speed BSCM/ABS fault codes.