P20FB: Reductant Pump B Control Performance/Stuck Off

P20FB is the functional check of reductant pump B: its circuit is electrically sound, yet the pump does not reach the commanded state or stays off when it should be running. No public threshold exists for pump B. For pump A, Ford's 2023 diesel summary flags P208B when pump speed misses its setpoint by more than 300 rpm or the speed control sits at its limit for 30 seconds, which shows the principle. FCA names P20FB Reductant Pump 2 Control Performance and has listed it in a series of PCM reflash bulletins for the 3.0L EcoDiesel in Ram 1500, Wrangler and Gladiator (2020–2021, e.g. 18-028-21 and 18-002-23), so on those trucks a software update comes before any parts. Genuine causes are a worn, frozen or blocked pump or a clogged filter.

Symptoms

• Malfunction indicator lamp on
• DEF system warning, possibly with countdown to restart lockout
• Code returns mainly after cold starts or long parking

Most likely causes

• Outdated PCM software (FCA 3.0L EcoDiesel, reflash bulletins)
• Pump B worn, seized or blocked by crystallised fluid
• Frozen DEF or failed tank heating in cold weather
• Clogged pump filter or restricted lines

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the AdBlue/DEF level and quality, and do not add additives or water
2. Compare the reading with other engine data while varying the engine speed.
3. Look for white crystals around the injector and the tank
4. Check connectors and heaters with the scanner
5. Run the dosing test available on your diagnostic tool
6. Replace parts only when the test points to that component

Good to know

• Repair difficulty: hard
• It can trigger limp mode.
• It affects emissions.

What each character of P20FB means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 0: Subsystem depends on the code range
• FB: Specific fault in that system

Frequently asked questions

Can I keep driving with code P20FB?

Deal with it soon. If the instrument cluster shows a countdown, the car may not restart once it reaches zero.

What causes code P20FB?

The most common causes are: outdated PCM software (FCA 3.0L EcoDiesel, reflash bulletins); pump B worn, seized or blocked by crystallised fluid; frozen DEF or failed tank heating in cold weather.

Related codes

• P20FAReductant Pump B Control Circuit/Open
• P20FCReductant Pump B Control Circuit Low
• P20FDReductant Pump B Control Circuit High
• P208BReductant Pump A Control Performance/Stuck Off

Sources

• static.nhtsa.gov: MC 10190703 9999
• static.nhtsa.gov: MC 10231770 9999
• fordservicecontent.com: obd summary diesel 2023
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.