P0652: Sensor Reference Voltage B Circuit Low

The engine module feeds several sensors (camshaft, pedal, pressure sensors) from separate regulated 5 V reference circuits; 'B' is circuit 2. A short at one sensor pulls the whole reference down, so every sensor on it reports at once – unplug them one by one until the reference returns to 4.8–5.2 V. P0652 means reference B is too low – usually the 5 V line or a connected sensor is shorted to ground. GM's 6.6 L Duramax LB7/LLY (2004–05) sets it below 4.7 V for 2 s; GM Europe's 2.0 L turbo after 1 s or 10 s cumulative, each with the lamp in the first trip. Newer GM engines report it under the collective code P0651, and Ford does not use P0652. All sensors on the circuit then read low, with matching codes, limp mode and possibly starting problems.

Symptoms

• Check engine light
• Several 'low' sensor codes at once
• Limp mode or reduced power
• Starting problems

Most likely causes

• 5 V reference wire shorted to ground (chafing)
• Sensor on the reference circuit shorted internally
• Moisture or corrosion in a connector
• Module

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery and grounds
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Clear the code and see if it returns
4. If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
5. Check whether a software update is available
6. Do not replace the control module without a full diagnosis

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P0652 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 6: Control modules and outputs
• 52: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0652?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P0652?

The most common causes are: 5 V reference wire shorted to ground (chafing); sensor on the reference circuit shorted internally; moisture or corrosion in a connector.

Related codes

• P0651Sensor Reference Voltage B Circuit/Open
• P0653Sensor Reference Voltage B Circuit High
• P0642Sensor Reference Voltage A Circuit Low
• P0698Sensor Reference Voltage C Circuit Low
• P06A7Sensor Reference Voltage B Circuit Range/Performance

Sources

• law.cornell.edu: 13 CCR 1968.2
• saabwisonline.com: dtc p0641 p0643 p0651 p0653 or p0697 p0699 ecm
• gsi.ext.gm.com: 2004file9
• gsi.ext.gm.com: 2005file9

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.