Powertrain, generic · Computer and auxiliary outputs

P0698 Sensor Reference Voltage C Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

The engine module feeds sensors from several regulated 5 V reference circuits; a short at one sensor pulls the whole circuit down, so all its sensors report at once – unplug them one by one to find the culprit. Which sensors hang on circuit C depends on the maker – pedal sensor 2 is common to all: GM 2016–2025 feeds only pedal sensor 2 from it, the Saab 9-4X also the MAP sensor, the Saab 9-5 2.0 L turbo also throttle, crankshaft and A/C pressure sensors, and Bentley's 2026 Bentayga V8 lists its own set. P0698 means reference C is too low – usually a short to ground. GM's 6.6 L Duramax LB7/LLY 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 as P0697.

Likely causes

Short in the wire or sensor of a connected sensor
Chafing or water in harness or connector
A connected sensor faulty internally
Module internal voltage regulator

Symptoms

  • Check engine light
  • Several sensor codes at once (pedal, throttle, pressure)
  • Electronic throttle limp mode, reduced power
  • Possibly 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

P0697P0699P0642P0652P06A4

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