Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2006SUBURBAN C1500, 5.3 ZREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 202 (CHARGING SYSTEM)DIAGNOSTIC TESTSDTC P1638: PULSE WIDTH MODULATION SIGNAL OUT OF RANGECONDITIONS FOR SETTING DTC
2006 Chevrolet Suburban C1500, 5.3 Z
Conditions For Setting DTC
2006 Chevrolet Suburban C1500, 5.3 ZSECTION Conditions For Setting DTC
WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
- During the key ON test, the PCM detects a PWM signal greater than 65 percent for at least 5 seconds.
- Or, during the RUN test, the PCM detects a PWM signal less than 5 percent for at least 15 seconds.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.