I'm buying a used truck/SUV. It disclosed an engine light code p0128. My question is it more expensive to purchase parts & repair myself. Or would it be worth having a mechanic fix it & look it over?

Code 128 usually means the engine thermostat is not functioning correctly and may need to be replaced.

The code means the cooling system is not reaching normal operating temp.
The common cause is a faulty thermostat which you would replace.
It could be something else such as a faulty temp sensor.

This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

A code P0128 may mean that one or more of the following has happened:

• Low engine coolant level
• Leaking or stuck open thermostat
• Faulty cooling fan (running too much)
• Faulty coolant temperature (ECT) sensor
• Faulty intake air temperature (IAT) sensor

Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:

• Verify coolant strength & level
• Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
• Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
• Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
• If the above items check out good, replace the thermostat

REFERENCE: http://www.obd-codes.com/p0128

I hope this helps a bit!

The check engine light comes when the computer control unit (called the PCM) senses a fault in the electronic controls of the engine and/or the emission system, there are about 200 possible faults that turn the light on, to know what has developed a problem you must have the system tested, this is called an OBD2 fault code test, Kragen and Autozone parts stores do this testing for free.

2001 accent gl 1.6, p1123 code comes on. how can I repair it myself?

Hi, you have a faulty thermostat, so you should just need a thermostat, associated gasket (or gasket maker), and some fresh antifreeze. Consult a vehicle-specific manual for specifics on your particular engine.

More P0128 info @ http://www.obd-codes.com/p0128

Check your switches for the VSC, some get bumped on (due to their location) and some get stuck in the "on"position.

Replacing it is the only fix. Sounds like it may be sticking open slightly.

i understand why you want to do it yourself - it's expensive to have it done by a mechanic. that's because it's a major job to remove the engine, takes 4-5 hrs. i avoided having it done by having an honest mechanic i've been going to for a long time do something else (sorry, i don't know what) that fixed the problem temporarily. he told me it must be done after 90k miles or so, so i'm saving up.