My engine light is on but I'm not getting any codes. I had my truck diagnosed at Auto Zone many times before for other problems and they were very helpful. Is it possible that the light is malfunctioning? Or do I need to see the dealer?

If the Check Engine Light stays on, when the ignition switch is turned to ON, it may be indicating the PCM is failing.

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Originally Posted by TxGreaseMonkey

If the Check Engine Light stays on, when the ignition switch is turned to ON, it may be indicating the PCM is failing.

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Thanks. Is the pcm the main computer? Does anyone know ware its located in the Yukon?

Yes. It's likely located along the firewall (passenger's side) under the hood. Look for a large bundle of wires going to it.

Quote:

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Originally Posted by TxGreaseMonkey

Yes. It's likely located along the firewall (passenger's side) under the hood. Look for a large bundle of wires going to it.

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Thank you!