Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
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I agree with you on P1518 probably being caused by lack of electrical power.
I suggest recharging the battery so it reads a full 12.6 volts after after a load test. Start the engine and rev it to 2000 RPM. Turn on hi beams and A/C. Then measure voltage across battery negative post and alternator pole (where the big Red wire goes). Record that voltage and then measure across battery positive post and engine block. Both voltages should be above 13. If not, there is a charging system problem that needs further diagnosis.
Please let me know if you have any other questions.