Powertrain, generic · Computer and auxiliary outputs

P0653 Sensor Reference Voltage B Circuit High

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. P0653 means reference B is too high – often a signal wire of a connected sensor has chafed onto a 12 V line, less often the reference wire itself. GM's Duramax LB7/LLY (2004–05) sets it above 5.2 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 as P0651, Ford does not use it. Sensor readings then become implausibly high and limp mode follows.

Likely causes

Reference or sensor signal wire shorted to a 12 V line
Faulty sensor feeding in external voltage
Module voltage regulator

Symptoms

  • Check engine light
  • Several 'high' sensor codes
  • Limp mode
  • Implausible sensor values in live data

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

P0651P0652P0643P0699P06A7

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