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.
Code P1650, QDM No. 2: Notes
PCM is used to control several components as shown in wiring schematic. PCM controls these devises through use of a Quad-Driver Module (QDM). When PCM is commanding a component on, voltage potential of output circuit will be low (near zero volt). When PCM is commanding output circuit to a component off, voltage potential of circuit will be high (near battery voltage). Primary function of QDM is to supply ground for component being controlled.
Each QDM has a fault line which is monitored by PCM. Fault line signal is available on data stream for scan tool test equipment display on Tech 1. PCM will compare voltage at QDM based on accepted values of fault line. If QDM No. 2 fault detection circuit senses a voltage other than accepted value, fault line will go from a low signal on data stream to a high signal and Code P1650 will set. Code P1650 will set when the following conditions are present.
- Engine is running.
- PCM detects an improper voltage level on a circuit connected to QDM No. 2.
- Above conditions met for 5 seconds.
Code P1650 will not illuminate Malfunction Indicator Light (MIL).
- If QDM related code is stored, diagnose that code first. Repair made to related code will repair Code P1650 also.
- This test will determine which circuit is out of specifications.
- This test will determine if problem is circuit or component.
- As the factory installed PCM is protected with an internal circuit breaker, it is highly unlikely that PCM needs to be replaced.
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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.
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