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I had the exhaust off my car to sort out a weeping diff. It a standard exhaust so therefore had to come off where it connects to the manifolds (headers).
All 4 O2 sensors were disconnected but all replaced when the job was compelted. when i fired up the car the check engine light was on but the car ran perfectly as it did before. I've taken it to the dealer to have it reset (i guessed it had to learn parameters) and this solved the problem-they confirmed that no faults were present or stored.
However, when i switched the car off again and then restarted it about an hour later the light was on again!!
Does anyone know what has happened or how i can fix it??
 

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If you had no CEL before the work was done, then you need a new tech and/or a Peake. Resetting a CEL -- by itself -- is likely to solve nothing, and any tech that can't find the error code(s) thrown by a CEL would seem to be unreliable.
 

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Agree with Chowdah. My 1st impression is that you didnt connect the sensors COMPLETELY. You really have to push in hard on the plug in to ensure a good connection. The fault was probably pre-cat heater control. It wouldnt cause your car to run any differently.

1. Unplug, then re-plug all the connections back together with the above in mind.
2. Invest in a Peake code reader....Not a code reader from Autozone, or similiar. PEAKE reader. They are exclusive to these vehicles and priceless.

Good Luck

Steve
 
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