So I just got a P0128 error code for the ECT (02 XL Denali). However, there are no symptoms of ECT or Thermostat. Warms up quick enough, and over 200 in 35 degree weather. Seems unlikely thermostat is stuck open. Temp gauge is working properly, so it doesn't seem like it is the sending unit. If I take it apart, I'll do both I anyway just to keep from draining it twice. Any thoughts?
P-128 ECT
- Thread starter WhyJ
- Start date
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mattbta
Full Access Member
If you're quick, you can swap the ECT sensor out without much loss. Maybe drive on ramps so the coolant in the head runs to the back?
Not exactly your issue, but Eric O recently posted a video about diagnosing a Trailblazer that wouldn't complete a drive cycle. Turns out two (maybe three, including the original) ECT sensors were far enough off spec that the drive cycle couldn't complete. Might be worth comparing the IAT with the ECT on yours.
