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2003
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Silverado 1500 HD, RWD
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DTC P1638: Pulse Width Modulation Signal Out Of Range
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Conditions For Setting DTC
Conditions For Setting DTC
During the ignition ON test, the PCM detects a PWM signal is out of range.
During the RUN test, the PCM detects a PWM signal less then 5 percent for more than 6 seconds.