P0653 Sensor reference voltage: signal or voltage too high (reference voltage, "B")

By: Diagno editorial team · Updated: 2026-10-15

P0653 means: Sensor reference voltage: signal or voltage too high (reference voltage, "B"). The computer feeds the sensors a 5-volt reference voltage. Drive gently and have the car checked soon. The most common repair costs about €45–90 in Estonia, depending on make and model. The most common cause: connector loose, damp or corroded.

What it means

The computer feeds the sensors a 5-volt reference voltage. That voltage is missing, too low or too high, so several sensors may read wrong at once. The signal voltage is too high. Usually a wire is shorted to power, the ground is broken or the part itself has failed.

What you may notice

• Several fault codes at once
• Limp mode
• The engine may not start

What could be wrong

1. 1Connector loose, damp or corroded · Wiring or connector repair €45–90
2. 2Wire shorted to power or ground broken · Wiring or connector repair €45–90
3. 3Faulty sensor · Sensor replacement €80–160
4. 4Engine computer fault (rare) · Control unit check and software €150–300

Repair difficulty: Moderate

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? If several sensor faults appeared together, a shared supply is probably the cause. Check connectors that were recently disturbed. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the sensor

Standard SAE description: Sensor Reference Voltage "B" Circuit High