P20D3 Exhaust Aftertreatment Fuel Injector B Control Circuit Low

The control line of the second exhaust fuel doser (B) is pulled toward ground. No manufacturer documents P20D3 publicly. For injector A, GM's diesel tables detect this by a switched-off output voltage below about 2 V and treat it as Type A with the MIL after one trip (P20CD), because a grounded line can open the valve without command. A similar strict rating is likely for B. CARB requires each electrical part of an in-exhaust injection system to be checked for circuit faults. The open circuit is P20D1, the short to power P20D4. Only engines with two dosing points can set this code.

Likely causes

Symptoms

• Check engine light on
• Doser B switched off, regeneration impaired

Repair estimate

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

Parts involved

Related codes

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