Powertrain, generic · Computer and auxiliary outputs

P0652 Sensor Reference Voltage B Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

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

Symptoms

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

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–600
Time1–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

sensor reference voltage circuitsensor wiringengine control module

Related codes

P0651P0653P0642P0698P06A7

References: law.cornell.edu, saabwisonline.com, gsi.ext.gm.com, gsi.ext.gm.com.