P0128 on Jeep Vehicles
The engine takes too long to warm up, which almost always points to a thermostat stuck open. P0128 →
12Complaints mentioning the code
#3Rank among 11 brands
1.9%Share of Jeep DTC complaints
In NHTSA owner complaints we analyzed for Jeep, P0128 was mentioned 12 times.
Most mentioned models
| Jeep Renegade | 6 | |
|---|---|---|
| Jeep Cherokee | 4 | |
| Jeep Grand Cherokee | 1 | |
| Jeep Patriot | 1 |
Model years mentioned
Components named in these complaints
- Engine (10)
- Air Bags (3)
- Electrical System (2)
- Power Train (2)
- Unknown Or Other (2)
Reports with a crash: 1 · fire: 0 · injuries: 0
Often appears together with
P0172
Powertrain
The engine computer is pulling as much fuel as it's allowed on bank 1 and the mixture is still…
Moderate
P0455
Powertrain
The fuel vapor system can't hold vacuum at all — check the gas cap first, then hoses and valves.
Low
P0456
Powertrain
The EVAP system has a tiny leak, about 0.020 inch — the hardest EVAP leak to find, and often…
Minor
Possible causes
- Thermostat stuck partly open or opening too early
- Coolant temperature sensor reading lower than the actual temperature
- Low coolant level or an air pocket around the sensor
- Radiator fan running constantly (stuck relay or faulty fan control)
Related codes
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.