Chassis, generic

C0870 Control Module Voltage Reference Output Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

C0870 is missing from the accessible J2012 code lists; it is documented at GM, where it covers the 5 V reference that a module feeds to its sensors. Saab workshop pages for the 2011 9-5 and 9-4X use it in the suspension control module, which feeds five acceleration sensors on the body and at the wheels: subcode 03 means that line is shorted to ground and 07 that it touches battery voltage, each for 1.5 s, checked between 9 and 16 V. Electronic damping then shuts off for the ignition cycle. The fix is to unplug the sensors one by one and watch the reference return to 4.8-5.2 V. Under the older name Device Voltage Reference Output 1 Circuit, GM hybrid pickups of 2005 and 2007 used it for the pedal sensor supply of the steering pump (above 4.65 V or below 3.95 V, type C, no MIL).

Likely causes

One acceleration sensor shorting the shared 5 V reference
Reference line chafed to ground or to battery voltage
Module reference supply faulty, module replacement after wiring checks (Saab WIS)

Symptoms

  • SERVICE SUSPENSION SYSTEM message
  • Adaptive damping inactive for the rest of the trip
  • Several acceleration sensor codes stored at once

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–900
Time0.5–3 h

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

Parts involved

sensor reference voltage circuitsuspension control modulevertical acceleration sensor

Related codes

C0670C0800C0920

References: saabwisonline.com, saabwisonline.com, gsi.ext.gm.com, gsi.ext.gm.com.