P027B: Fuel Pump Module B Control Circuit Range/Performance

On demand-controlled fuel systems the engine module does not drive the pump itself but sends a pump control module the desired pump output on a separate control line, usually as a duty cycle; the module reports back on a monitor line or via CAN. Module B is a second pump module, for example on dual-tank commercial vehicles. P027B means pump module B receives an invalid command or its feedback does not match. Ford's module signals this with a 20 % (±4 %) duty cycle on its monitor line, checked continuously at 11–16 V over 2–5 s; on Ford commercial vehicles the module B monitor line runs via the smart relay module and CAN to the engine module. Whether the warning light comes on depends on the vehicle.

Symptoms

• Check engine light (vehicle-dependent)
• Fuel shortage when running from the second tank
• Surging, lack of power

Most likely causes

• Contact resistance or corrosion in the control or monitor line to module B
• Pump control module B faulty
• Ground problems
• Relay module or CAN forwarding disturbed (Ford commercial vehicles)

What to check, in order

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

1. Check the pump's fuse, relay, and connector
2. Compare the reading with other engine data while varying the engine speed.
3. Replace the filter if it is due for maintenance
4. Compare commanded and actual pressure in live data
5. Measure the pressure with a suitable gauge
6. Check the sensor and regulator before replacing the pump

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P027B means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 2: Fuel injection
• 7B: Specific fault in that system

Frequently asked questions

Can I keep driving with code P027B?

Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.

What causes code P027B?

The most common causes are: contact resistance or corrosion in the control or monitor line to module B; pump control module B faulty; ground problems.

Related codes

• P025BFuel Pump Module A Control Circuit Range/Performance
• P025AFuel Pump Module A Control Circuit/Open
• P027CFuel Pump Module B Control Circuit Low
• P027DFuel Pump Module B Control Circuit High
• P2632Fuel Pump B Control Circuit/Open
• P26EAFuel Pump Control Module B

Sources

• law.cornell.edu: 13 CCR 1968.2
• fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
• roushcleantech.com: Roush CleanTech Diagnostics Manual DA 8.5.18

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.