[bshane]

I have a 2002 subaru forester with 104,000 miles

8/22/12 I had the thermostat, timing belt, and water pump

recently replace valve cover gaskets, spark plugs, oil change regularly

when I am driving around town the thermostat runs just fine
when I get up to highway speeds my thermostat drops to Cold
it only started to do this when the temperature dropped here in denver
its been in the 20s and 30s i dont think that would have too much to do with it


the check engine light came on when it did this last night and i had the code checked on my way to work
its saying

1- A/F ratio is off
2- Ignition malfunction
3- Catalytic converter failure

the car is running strong and smooth not noticing anything wrong
all fluids are at proper levels
would this be a faulty alternator?

im stumped, anyone have any suggestions on where i should start?

any suggestions would be much appreciated

 

[flstffxe]

1. Get the actual Pxxxx code for the cell and let us know what it is.

2. Check the coolant level in both the radiator and the overflow bottle.

3. What positions do you have all the climate controls in?

My initial suspicions:
- I am suspect that the thermostat may have failed in the open position.
- Coolant level may be low
- Coolant temp sensor wiring issue(doubtful since it only happens on the highway)

 

[toysbyus]

I agree and suspect that the new (?) thermostat is defective or installed backwards?

Steve

 

[Easy Fixer]

Check the ECT

You have a poorly connected engine coolant temperature sensor or a defective one. Replace it. All the CEL codes are because the ECT affects many of the other sensors.:Banane08:

 

[jgrote]

There are 2 temp sensors on your car. One controls only the gauge. The other one sends a signal to your ecu when the car reaches a set temp. It's more of an on/off switch than a sensor. The one with 1 wire is the ecu sender. The one with 2 or 3 wires is the gauge. I doubt your problem is with both. It sounds as if your coolant is free flowing through the system, or the coolant going by the sensors is not going through the engine first. I would replace the t-stat with a genuine subby one first.