P0650: MIL Control Circuit/Open

What does P0650 mean?

The engine module switches the check engine light (MIL) through a low-side driver – or sends the command over CAN – and monitors the circuit: with the lamp off the line must carry supply voltage, with it on nearly 0 V. CARB requires the MIL to light for a bulb check at ignition on with the engine off (at least 15 s since model year 2005). GM's 2018–2025 modules use P0650 only for an open circuit (200 kΩ or more, above 11 V, 50 ms) and P263A/P263B for shorts to ground and voltage – stored without lighting the MIL, since a broken MIL cannot report itself; older GM diesels combine all faults in P0650. GM Europe's Saab 9-5 V6 checks only once the MIL has been commanded on and off. The engine runs normally, but emission faults go unseen and inspections fail if the lamp does not light at the bulb check.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• MIL does not light at the bulb check
• MIL stays on (with a short or combined code)
• Code only visible with a scan tool, engine runs normally
• Failed emissions inspection

Common causes

• High Wire or connector between engine module and instrument cluster open or corroded
• High MIL bulb burnt out or LED/instrument cluster faulty
• Medium MIL supply in the cluster missing (fuse, ignition feed)
• Medium Short in the circuit (at GM reported as P263A/P263B)
• Low Output driver in the module faulty

Likelihood is a general estimate across vehicles; your make and model may differ.