Jeep code
P0128: on a Jeep
How much to fix P0128 on a Jeep? Typically $100 to $420 for thermostat replacement, the most common fix. This is an estimate, not a quote.
P0128 means the coolant took too long to reach normal temperature. On Jeeps, that is nearly always a thermostat that stays open, but a bad coolant sensor can look the same.
General meaning of P0128: After a cold start the computer expects the coolant to climb to its normal running temperature within a set time. On this drive it stayed too cool for too long. The usual reason is a thermostat that stays partly open and lets coolant flow through the radiator when it should not. See the full P0128 page.
Models to know about
| Model | Years | What to know |
|---|---|---|
| Grand Cherokee | 2011 to 2019 | The 3.6 Pentastar thermostat can be tied to the housing. |
| Wrangler | 2007 to 2018 | The 3.8 and 3.6 engines both appear. |
| Cherokee | 2014 to 2019 | The 2.4 and 3.2 engines. |
| Patriot | 2007 to 2017 | Smaller 2.0 and 2.4 engines. |
Common causes on a Jeep
- Thermostat stuck partly open. This is the most common cause on Jeeps.
- Coolant temperature sensor that reads low.
- Low coolant level or air in the system after a repair.
- Cooling fan that runs when it should not.
NHTSA's public complaint file shows how owners describe this kind of trouble: the 2013 Jeep Grand Cherokee has 805 complaints on file, and 38 of them use wording like thermostat, coolant, P0128, heater; the 2012 Jeep Wrangler has 835 complaints on file, and 71 of them use wording like thermostat, coolant, P0128, heater. Complaints are owner reports, not proof of a cause.
Check this first
- Check heater output. Cool air in winter with a long warm-up is a hint.
- Check coolant level cold.
- Ask for live coolant temperature data to compare with a thermometer.
Wide range: this job varies a lot. Itemize your quote for a better answer.
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $10 | $90 |
| Labor: 0.8 to 2 hours × $110 to $150 an hour | $88 | $300 |
| Fees: shop supplies, disposal, diagnostics | $10 | $25 |
| Total, rounded | $100 | $420 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in the US, $27.13 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
On many Jeeps the thermostat is part of a housing, so the part is pricier than a plain thermostat. Ask which one is quoted.
Other repairs that may be involved
| Repair | Typical range, US |
|---|---|
| Thermostat replacement | $100 to $420 |
| Coolant temperature sensor replacement | $90 to $240 |
| Coolant flush and refill | $110 to $330 |
Questions to ask the shop
- Is the thermostat only or a housing?
- Did you check the sensor?
- Will you bleed the coolant system?
Got a quote already? Check it against the range. Wondering if a recall touches this problem? See Jeep recalls by model or check a VIN.
P0128 on a Jeep: questions
Can I drive with P0128?
Yes, short term. A cold engine hurts mileage and heat, but is not an emergency.
Will it fail an emissions test?
Likely yes, until fixed.
How much does it cost to fix P0128 on a Jeep?
The most common fix, thermostat replacement, has a typical range of $100 to $420 across the US. That is an estimate built from parts prices and local labor wages, not a quote. Your model, engine and shop move it.
Sources
- NHTSA complaints, 2013 Jeep Grand Cherokee
- NHTSA complaints, 2012 Jeep Wrangler
- NHTSA recall lookup by VIN
Written from public NHTSA data, owner-reported patterns and general repair knowledge, in our own words. Model lists are examples, not a full list, and patterns are not a diagnosis. Prices updated October 2026. Not a repair shop, estimates only.