Mechanics

ERROR CODE P0128

2003 Cadillac CTS

Engine Cooling problem
2003 Cadillac CTS 6 cyl Two Wheel Drive Automatic 105000 miles

I've got an error code P0128 on an 6 cyl 03 CTS Caddy. The book claim's engine coolant temp below normal. Not sure but seams to me that the thermostat is stuck open. Could be a bad sensor but want to say it would go full scale if faulty. I read from a previous post that you have to go behind the timing belt to get to the thermostat. What speical tools are needed to reset the timing? I don't mind getting greasey and have re-built many a motor with good results. The problem I have is paying the dealership $500.00/700.00 labor when I could do this myself on any given weekend.
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350ZMan
October 15, 2008.



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

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

3.2L Engine

Drain the cooling system.
Remove the radiator inlet hose from the coolant outlet pipe.
Remove the bolt securing the oil level indicator tube, coolant outlet pipe and engine front lifting bracket from the cylinder head.
Remove the coolant outlet pipe from the thermostat housing.
Remove the O-ring seals from the coolant outlet pipe. Discard the O-rings.
Remove the intake manifold.
Remove the thermostat housing bolts.
Remove the thermostat housing with thermostat, from the engine.
Remove and discard the seal ring.
Remove the thermostat from the thermostat housing.
To install: Install the thermostat into the thermostat housing.
Install a new seal ring.
Position the thermostat housing with thermostat, to the engine.
Install the thermostat housing bolts and tighten to 15 ft. Lbs. (20 Nm).
Install the intake manifold.
Lubricate 2 new O-ring seals with coolant.
Install the new O-ring seals around the coolant outlet pipe grooves.
Insert the coolant outlet pipe (3) into the thermostat housing.
Install the bolt securing the oil level indicator tube, coolant outlet pipe and engine front lifting bracket to the cylinder head and tighten to 15 ft. Lbs. (20 Nm).
Connect the radiator inlet hose to the coolant outlet pipe.
Fill the cooling system.

Jnovack
Oct 15, 2008.
Thanks jnovack,
Cooling fans are fine. Guess ECT & IAT sensor's don't have their own code? What should the coolant temp. Be at idle? (I hate idiot lights) Is there a meter I can get my hand's on to test the sensor's?

Thermostat replacement sounds like a cake walk, I was thinking radiator inlet hose entered the engine about mid way down on the right side(daughter's car) guess I was wrong.

Are there tork spec's for the intake manifold?

Sounds like it's time to get your online e-repair manual. Are they any good?

Tiny
350ZMan
Oct 15, 2008.
Intake manifold spacer. Torque the bolts in a spiral direction, starting from the inside and working outward to 15 ft. lbs. (20 Nm).
Intake manifold. Torque the bolts to 15 ft. lbs. (20 Nm).
Intake air resonator. Torque the nuts to 27 inch lbs. (3 Nm).(Note this is inch punds not foot punds)
Intake plenum. Torque the bolts to 71 inch lbs. (8 Nm).(note this is inch punds not foot punds)
this link can get you the tools you need thank you

http://www.2carpros.com/affiliate/uid/jnovack_1

Jnovack
Oct 15, 2008.