Faulty thermostat causing SES light to illuminate on Chevrolet Trailblazer

Average mileage: 121,019 (50,000–215,159)
Engine affected: 4.2L 6 Cylinder
4 model years affected: 2003, 2005, 2006, 2007
9 people reported this problem
9 people shared problem details
This vehicle has a thermostat that fails in the open position which causes the temp gauge to drop below normal and heater to fail. The thermostat is located on the driver's side of the engine behind the alternator. You might need to remove the wheel to access the mounting bolts. You will need multiple rachet extensions and some patience. Dealer wants $500 to replace thermostat. Do it yourself for less than $100.
2005 Chevrolet Trailblazer- 4.2L 6 Cylinder50,000
Replaced thermostat twice, dealer said it needed to be changed again or maybe it's just a bad sensor :-(
2006 Chevrolet Trailblazer- 4.2L 6 Cylinder180,000
Ses light stays on. Had to replace multiple parts. Now it is the thermostat.
2003 Chevrolet Trailblazer- 4.2L 6 Cylinder105,000
service engine light came on. was told it could need engine coolant or was the thermostat. let problem go with out doing anything. bout a year later had to have a catalytic converter replaced. do not ignore engine lights. cost way more down the road
2003 Chevrolet Trailblazer- 4.2L 6 Cylinder73,000
ought car used. When arrived home check engine light on. Check code- thermostat. replaced. no light or code
2003 Chevrolet Trailblazer- 4.2L 6 Cylinder215,159
temp gauge read around 110 but the heat was hot . also check engine light was on
2007 Chevrolet Trailblazer- 4.2L 6 Cylinder128,000
Had the same problem.
2007 Chevrolet Trailblazer- 4.2L 6 Cylinder
Check engine light came on. Had it checked and code came back to thermostat
I actually had my thermostat replaced after a faulty reading
Related Items:
From all my research, it seems that this code mean I -(hubby) needs to replace the thermostat....
I'm getting a P0128 CODE on my Trailblazer. It is caused by a defective temperature sensor or t...
warning lights come on checked with code reader and got no codes
I got this vehicle recently. The service engine light was on. I got the codes checked and say...

Related Content