2003 Cadillac CTS Engine light on and no heat on driver's side.

  • 6 CYL
  • FWD

I own a 2003 Cadillac CTS. The engine light is on, I have no heat on the driver's side and the car is vibrating. I had it looked at by three different mechanics, all of which have not helped. I had the thermostat changed to a new one and the heat is still not working on the driver's side.

I was told the engine is heating up 50%, from what they said it is suppose to heat up at 95-100%

I had a diagnostic test and these were the codes: diagnosis because of engine trouble indicator light / diagnosis heating (left is not hot) test computer: Error Code P0128 Coolant Temp. Low/P0856 TCC torque req. Failed/C1277 signal/C1244 engine drag torque control controllscript Malfunction.

I was told the heating Valve has to be replaced in order to fix the heat in the drivers side and that may also stop the car from vibrating. They said to replace the valve it will take 8-10 hours of labor. Is this true?

They also told me the gasket cover is cracked, so now they have to replace all six sparkplugs, gasket and gasket cover. Is this accurate?

Please provide me with any opinions/advice you may have regarding my car.

Thanks in advance,
Do you
have the same problem?
Wednesday, March 2nd, 2011 AT 3:00 PM

1 Reply

First, if you get heat on one side and not the other, the heater is working. The problem is related to what is called a blend air door. On vehicles with dual climate control, there are two blend doors. The door's function is to determine if you get heat or AC in the vehicle based on its position. Based on your description, one is not working. As a result, the actuator could be bad or it could be stuck. I hate to say it, but it is a major job to access. Most of the dashboard needs removed to access it. Eight hours sounds about right. Will that stop the vibration? I doubt it. However, the TCC is a concern for a vibration. The torque converter, if engaging OD too soon can cause it. The C1244 tells me the RPM's may be dropping too low and that can cause a vibration.

As far as the "gasket cover" has me confused. Are they refering to the valve cover gasket? Also, if you replace them, it would be an easier time to replace the plugs, but you don't have to. I don't know how many miles are on the vehicle or when they were last replaced, so it is hard to say if they should be replaced.

One last thing. The fact the engine doesn't warm up properly is setting other codes. If the t-stat was replaced, it still may be bad. The thermostat shouldn't fully open until 195 F. If it doesn't warm up, the t-stat is opening too soon and staying open. Otherwise, the engine would heat up. Pay attention to the cooling fans. Make sure they are not turning on. They shouldn't turn on until aprox 215 F. If they turn on, they will cause the engine to cool down quicker.
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Thursday, March 3rd, 2011 AT 6:14 PM

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