P0643

Symptoms

• Check Engine light comes on
• Several sensor codes at the same time with inflated values
• Engine emergency mode
• Incorrect mixture formation (mixture too rich)
• Unstable engine operation

Causes

• Short circuit of the reference voltage wire to the power wire
• Internal fault of the ECU (voltage reference generator)
• Damage to the insulation of the wiring harness (positive contact)
• Incorrect connection after repair work
• Faulty sensor with internal short to positive (rare)

How to Fix

1. Check voltage at circuit A sensor reference pins
2. Check the reference voltage wire for short to power wires
3. Inspect the wiring harness for damaged insulation
4. Disconnect the sensors one at a time and check if the voltage changes
5. If the wiring is in good condition - diagnostics of the ECU using specialized equipment
6. Replace the ECU if it is confirmed to be faulty

Related codes

Error P0643 by Vehicle Brand