P2535 — Ignition switch signal stuck high during run/start

The ignition switch is sending a constant 'on' signal when it shouldn't, indicating a problem in the run/start circuit. This can happen due to a faulty ignition switch, wiring issues, or a bad connection. The car’s computer detects this abnormal voltage and triggers the code.

Common causes

The cause is almost always one of a few things. Here they are — P2535 rarely comes from anything outside this list:

• Faulty ignition switch
• Damaged or shorted wiring in ignition circuit
• Loose or corroded ignition switch connector
• Malfunctioning ignition lock cylinder
• Faulty body control module (rare)

Where to start

In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:

1. Check and clean ignition switch connectors
2. Inspect wiring harness for damage or shorts
3. Test ignition switch operation with multimeter
4. Replace ignition switch if faulty
5. Replace ignition lock cylinder or related modules if needed

That is what holds for P2535 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.