Powertrain, generic · Computer and auxiliary outputs

P0656 Fuel Level Output Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

The engine module switches this hard-wired output with its own driver and checks the circuit electrically (open, short to ground or voltage) – it cannot see whether the lamp lights; on CAN-based cars such faults appear as U codes. Where the engine module reads the fuel level sender itself – it needs the level for the evaporative leak test – it passes the level on to the fuel gauge. GM Europe's 2010 Saab 9-5 reads two senders (0.5–3.5 V), calculates the level in percent and sends it over CAN via the body module to the instrument cluster; there a failure would be a U code. P0656 reports a fault on a hard-wired level output. No manufacturer document available to us uses this code; the description follows CARB and the component. The gauge then reads empty, full or jumps and the low fuel warning is wrong; engine and evaporative test are not affected. Sender input faults are P0460–P0464.

Likely causes

Wire or connector between module and instrument cluster open or shorted
Instrument cluster (fuel gauge input) faulty
Output driver in the module faulty
Fuel level sender fault as root cause

Symptoms

  • Fuel gauge reads empty, full or jumps
  • Low fuel warning wrong
  • Range display wrong

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–450
Time0.5–2 h

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

Parts involved

fuel level output circuitfuel gaugeengine control module

Related codes

P0460P0461P0462P0463P0464

References: law.cornell.edu, saabwisonline.com.