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06 DTS with Engine Light on, P0036 code

13K views 8 replies 5 participants last post by  Superjim 
#1 ·
We have a 2006 DTS with 60,000 miles on it. A day after filling up with high octane gas (we alternate between 87 and the highest, on the recommendation of the dealer), the engine light came on. We took it to a local mechanic, who said it was the O2 sensor (P0036 code). He replaced the sensor, light went off...but came back in about a week. Took it back in, he now says it's the ECM, that they fail regularly. Went up to Cadillac dealer, who replaced the ECM. Light goes off...back on within a few days. Back to Cadillac, who tells us the O2 sensor must be bad (the new one) and to go back to the mechanic. Did so...they switched out sensors, and this time the light is on right off the bat.

We've replaced the gas cap (from another thread suggestion). Once, after a fill up, the engine light went off, but came back on when the gas got low. Filled up the tank, light goes off for a few days, but then back on. As a side note, the car runs great...no "missing" or any other issues.

Just checked via Onstar, and the codes are P0036 and P0054 now.

We had planned to get a newer DTS, but with the engine light continuously on, who the heck would want to buy our car??? We are at our wits end. Anybody have any suggestions?
 
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#2 ·
If I am not mistaken..
P0036 is the Oxygen sensor Heater Control Circuit for Bank 1 Sensor 2
P0054 is the Heater Resistance Bank 1 Sensor 2

Possible causes are...
Heated oxygen sensor harness open or shorted
Heated oxygen sensor circuit poor connection

It is probably NOT the actual sensor itself.. it is most likely in the circuit wiring going to the sensor.

Texas Jim
 
#3 ·
It is definitely an electrical issue with your o.s. The second code was surely triggered by (1) either a failure to address the initial problem or (2) one of the two mechanics compounded the issue while attempting to fix it. Another thing that may explain the failure to resolve the issue on the first attempt: there are 3 o.s. I am encountering a similar electrical problem with a p0049. I am waiting for this bad weather to pass to get under the car. I just received a connector that I am waiting to install.
 
#4 ·
look for the sensor with a pk/bk wire coming from the p21 fuse this is the bad one the other two sensors the pk/bk wire come from the p22 fuse

The bk/wh wire from it to the ecm is a good starting point look for high resistance in that wire this should be the only sensor with a bk/wh wire this is the wire for the voltage low control. Im not sure this sensor is swappable. Mike
 
#5 ·
A couple more things the sensor is on the bank by the radiator lift the car and remove the air deflector to get at it if sensor removed it has to be installed with anti seize at 30ft lbs torque, to avoid possible failure of the new sensor a heater resistance learn reset should be done and a code clear whether or not a dtc was set.

Pin c on the harness connector is bk/wh pin d is pk/bk.Mike
 
#8 ·
The rest of the story...

My husband, armed with all this great info from all of you, took the car up to our dealership. He told them, "Don't call me until it's fixed!" LOL! They ended up replacing a wire that leads to the sensor(s?) and voila! No engine light, the remote start works again, and life is good.

Sure appreciate all of your good advice, and especially this forum to look to when issues arise.
 
#9 ·
Glad you got it fixed without being charged an arm and a leg for a lot of stuff that wasn't necessary...

Without this info... they would probably have replaced the sensor, then when that didn't fix the problem, they would have fixed the wire and then charged you for both. :) :)

Texas Jim
 
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