Code P0128

Macintoshuser

Newbie
Points
0
From
Miami, FL
Car
2003 Toyota Corolla
I have a 2003 Toyota Corolla CE model with just 170, 681 miles on it. I changed the radiator, thermostat, & temperature sensor at 169,556 miles after I had over heated it. I got a check engine light that's giving me code P0128 which I've attached a picture of it. The thermostat and sensor are new so I don't know how it could be failing. The only thing I can think of is that I burned the head gasket when it over heated and it's causing combustion to either make the temperature sensor get a bad reading or damage the thermostat. The problem with that though is that I'm not getting white smoke out of the tail pipe and I'm not getting milky oil. When I turn on the engine with the the radiator cap off I do get bubbles sometimes though. It seems weird that a new thermostat and or a temperature sensor would already start failing. I suspect it's the head gasket. What do you think?
 

obi_waynne

Administrator
Staff member
Moderator
Points
887
From
Deal, Kent UK
Car
A3 1.4 TFSI 150 COD
Ok first thing is to check the wiring at the temp sensor and make sure both the sensor wires are clipped back in and did not pop.

It's quite common for the clip to break on these.

It is also worth checking that you didn't cut or cause a short on one of the wires on the wire bundle near the passenger side as grounding of this can cause a fault code to appear.

The new temp sensor or thermostat could be faulty! Can you check them with a volt meter and hot water?

If the head gasket is failing you'll get a whitish mayonnaise forming under the filler cap, so I doubt it is the head gasket!

The water pump may also be failing to circulate the water around the engine, and check the entire water system for bubbles making sure you bleed out any air, as an air pocket can jam up the water flow.
 
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