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P0652 – Sensor Reference Voltage B Circuit Low (OBD2)

P0652 means "Sensor Reference Voltage B Circuit Low". The voltage the control unit measures in the sensor reference voltage circuit circuit is below the permitted minimum. For a sensor this usually means the signal wire is shorted to ground or the reference voltage is missing; for an actuator, that its control wire is shorted to ground.

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P0652 quick summary

Fault codeP0652
MeaningSensor Reference Voltage B Circuit Low
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityHigh
Can I drive?Not recommended. Several sensors fail at once, usually with limp mode, stalling or no start.
Repair cost€0 – €500

What the sensor reference voltage is

The control unit supplies a stable 5 V reference to many sensors; these codes mean one of the reference circuits (A, B or C) or the actuator supply voltage is shorted or open.

Sensors such as MAP, throttle position, pedal position, rail pressure and camshaft sensors receive a 5 V reference from the control unit. To limit the effect of a fault, the control unit usually has several separate reference circuits (A, B, C), each supplying a group of sensors. P0657–P0659 cover the separate supply for actuators.

If one sensor or wire shorts the reference to ground, the voltage drops and every sensor on that circuit fails at once. That is why reference voltage codes often come with many other sensor codes and limp mode.

The quickest way to find the fault is to unplug the sensors on the affected circuit one by one while watching the reference voltage: when it recovers, you have found the shorted sensor.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 17036 (P0652). Both numbers mean the same fault.

Symptoms of P0652

  • Several sensor codes at the same time
  • Limp mode or no start
  • Throttle or pedal not responding
  • Engine stalls
  • Check Engine and EPC lights on

Most common causes of P0652 (most likely first)

Mechanic's Pro Tip

Do not replace the control unit for a reference voltage code until every sensor on that circuit has been unplugged and tested. A single faulty sensor is by far the most common cause.

  1. 1.Signal or control wire shorted to ground

    Most likely

    Look for chafed insulation where the harness touches the engine, exhaust brackets or body edges.

  2. 2.Missing 5 V reference or supply voltage

    An open reference wire or a shorted sensor elsewhere on the same reference circuit can pull it down.

  3. 3.Internal short in the sensor reference voltage circuit

  4. 4.Water in a connector

  5. 5.Control unit reference output fault

Step-by-step diagnostic guide

  1. 1

    Read codes

    Read all codes and list which sensors report faults – they share the affected reference circuit.

  2. 2

    Measure the signal voltage

    With the ignition on and the sensor reference voltage circuit plugged in, back-probe the signal wire. Then unplug it and check the reference/supply and ground wires separately.

    Multimeter: Signal near 0 V = short to ground or no reference. Reference wire: about 5 V with ignition on. Signal wire to ground with connector unplugged: no continuity.

  3. 3

    Measure the reference voltage

    Measure the reference at one of the sensors.

    Multimeter: Normal: about 4.9–5.1 V. Near 0 V = short to ground; above 5 V = short to voltage.

  4. 4

    Unplug sensors one by one

    While measuring, unplug each sensor on the circuit. When the reference recovers, that sensor (or its wiring) is the cause.

  5. 5

    Inspect wiring

    If unplugging sensors does not help, inspect the harness for chafing and shorts.

  6. 6

    Repair and clear

    Replace the shorted sensor or repair the wire, then clear codes.

Frequently asked questions

Can I keep driving with P0652?

Not recommended. Several sensors fail at once, usually with limp mode, stalling or no start.

How much does it cost to fix P0652?

Typical repair costs are 0 € – 500 €, depending on the cause and the vehicle. The most common fixes are: signal or control wire shorted to ground; missing 5 V reference or supply voltage; internal short in the sensor reference voltage circuit. Always confirm the cause with the tests above before buying parts.

Why do I have so many sensor codes at once?

Because several sensors share the same 5 V reference. If it fails, they all report faults together.

Can a bad sensor damage the control unit?

Control units are protected, but a long-term short can damage the reference output. Fix it promptly.

What is the difference between P0652 and similar codes?

P0652 belongs to a group of codes for the same component that differ in the type or location of the fault: P0642 – Sensor Reference Voltage A Circuit Low; P0643 – Sensor Reference Voltage A Circuit High; P0651 – Sensor Reference Voltage B Circuit/Open; P0653 – Sensor Reference Voltage B Circuit High; P0657 – Actuator Supply Voltage Circuit / Open; P0658 – Actuator Supply Voltage Circuit Low. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.