Powertrain, generic (extended)

P26B4 Fuel Shutoff Valve A Control Circuit Stuck On

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P26B4 is the opposite failure to P26B3: shut-off valve A stays open or energised when the module wants it closed. No manufacturer documents P26B4 in public sources. On the Roush propane system for Ford trucks, valve A is the tank solenoid (its open-circuit code is P0005), and GM's 2015 Impala Bi-Fuel uses two normally closed CNG cut-off valves that the ECM opens only in gas mode while the engine cranks or runs. A valve that cannot close defeats that safety function, so fuel may keep flowing into the lines after shut-off. Typical causes are a short to voltage on the control wire, a stuck driver or relay, or a mechanically jammed valve. CARB requires output monitoring. Have it fixed promptly; close the manual tank valve if fuel can be smelled.

Likely causes

Control wire shorted to battery voltage
Supply relay or driver stuck on
Valve A mechanically jammed open

Symptoms

  • Check engine light
  • Fuel odour after shut-off
  • Fuel pressure remains in the lines with the engine off

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–800
Time1–3.5 h

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

Parts involved

fuel shutoff valve asolenoid

Related codes

P26B3P26B6P0005P0007

References: law.cornell.edu, roushcleantech.com, static.nhtsa.gov.