Emissions

P2BBD — Reductant Pump B Control Circuit Open

Severity: medium Drive with care, to a shop

What P2BBD means

The control module monitors the control circuit of reductant pump B and detected an open circuit or no load. Pump B is found on SCR systems with two pumps; it delivers diesel exhaust fluid (DEF) toward the injector to cut nitrogen oxide emissions. With the circuit open, the module cannot command the pump and DEF pressure is not correct.

Symptoms

  • Check engine light and a DEF/SCR warning on the dash
  • Low reductant system pressure
  • Possible reduced power or limp mode
  • Message about an upcoming speed or restart limit
  • Increased NOx emissions

Possible causes

  1. Failed reductant pump B (open motor winding)
  2. Open wire in the pump control circuit
  3. Corroded, loose or damaged pump or control module connector
  4. Damaged wiring harness (chafed, heat damage, corrosion)
  5. Faulty SCR control module or engine control module
  6. Blown fuse or a power supply problem to the pump

How to diagnose

  1. Scan all codes and freeze frame data; look for other SCR or power supply codes
  2. Inspect the connectors and harness at pump B and the control module for corrosion, moisture and chafing
  3. Check the pump fuse and relay
  4. Check power, ground and the control signal at the pump connector using the factory wiring diagram
  5. Test the control circuit for continuity from the module to the pump with connectors unplugged
  6. Measure pump B winding resistance and compare with spec
  7. Run the scan tool pump active test and watch system pressure
  8. If wiring and pump are good, evaluate the SCR control module

Common fixes

  • Repair the broken wire or replace the damaged harness section
  • Clean and secure the connector, or replace damaged terminals
  • Replace reductant pump B
  • Replace the fuse after finding the cause of the failure
  • Replace or reprogram the control module if it is confirmed faulty

Questions and answers

What does P2BBD mean?

The control module found an open circuit in the control wiring of the second reductant (DEF) pump in the SCR system. The pump, a connector or the wiring is the usual culprit.

Can I drive with P2BBD?

For a short time, yes, but the exhaust treatment is not working. The vehicle may cut power or refuse to restart, so get it diagnosed soon.

Will adding DEF fluid fix it?

No, not if the fault is electrical. Topping off only helps when the fluid level is low, and this code points to an open pump circuit.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.