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Home / DTC / P0256 — Injection Pump Fuel Metering Control B (Cam/Rotor/Injector)

P0256 — Injection Pump Fuel Metering Control B (Cam/Rotor/Injector)

Detailed page for trouble code P0256.

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23,694specific
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Code

P0256

Generic P — Powertrain

Injection Pump Fuel Metering Control B (Cam/Rotor/Injector)

Brand: Generic
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in the fuel metering control B wiring or connector
  • Corroded or loose connector at pump/solenoid
  • Faulty fuel metering solenoid, actuator, cam/rotor or meter assembly
  • Low fuel supply/pressure or clogged filter affecting pump response
  • ECM/PCM output driver failure
  • Intermittent wiring damage (chafing, pinched harness)

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Hard starting or extended cranking
  • Loss of engine power, poor acceleration
  • Rough idle or misfire under load
  • Reduced fuel economy
  • Intermittent engine stalling or limp-home mode

What to check

  • Retrieve freeze-frame and freeze data with a scan tool; confirm P0256 is active vs. historical
  • Inspect wiring and connector at injection pump B for corrosion, damage, pins pushed out or water intrusion
  • Check battery voltage and ground integrity at pump harness
  • Backprobe control connector and monitor signal while cranking/starting and at idle
  • Measure resistance of metering solenoid/actuator and compare to specification
  • Use a lab scope to view PWM duty cycle and waveform from ECM to solenoid

Signal parameters

  • Control signal type: PWM pulse-width modulated drive (ECM to solenoid/actuator)
  • Expected voltage range: approx. 0–12 V (varies by vehicle; when saturated ~battery voltage, when off ~0 V)
  • Typical duty cycle: 0–100% depending on commanded fuel metering (varies with engine load)
  • Typical frequency range: tens to a few hundred Hz (commonly 50–500 Hz)
  • Solenoid coil resistance: vehicle-specific — check service specification (often a few ohms to tens of ohms)

Diagnostic algorithm

  1. Use a scan tool to confirm P0256 and note freeze-frame parameters (engine speed, load, battery voltage, fuel pressure). Clear code and attempt to reproduce.
  2. Visually inspect connector and wiring to injection pump B. Repair or replace any damaged wiring or corroded terminals.
  3. With key on engine off (KOEO) and battery charged, measure voltage and ground at pump connector. Ensure stable battery voltage and good ground.
  4. Backprobe the control pin and monitor with a multimeter or scope while cranking and running. Verify presence of expected PWM signal and that duty cycle changes with throttle.
  5. Measure solenoid/actuator resistance. If open or shorted, replace solenoid/assembly.
  6. If electrical checks pass, check mechanical operation: verify fuel inlet pressure and that the pump/meters move freely (follow safe procedures; relieve fuel pressure before disconnecting).
  7. If intermittent, perform wiggle test of harness while monitoring live data to spot intermittent opens/shorts.
  8. If wiring and pump check good but signal is absent or incorrect, test ECM output driver. Swap with known-good circuit only if service manual allows, or bench-test ECM/driver per procedures.
  9. After repairs, clear codes and road-test to verify proper operation and that code does not return.

Likely causes

  • Broken or shorted control wire to metering solenoid B
  • Poor ground or battery voltage at pump control connector
  • Failed metering valve/solenoid on injection pump B
  • Fuel contamination causing sticking valve or rotor wear
  • Failed ECM driver for pump metering circuit B
  • Connector corrosion or water ingress at pump harness

Fault status

⚠️ Status
Injection Pump Fuel Metering Control B circuit or operation malfunction detected.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5 - 4.0 hours

Similar codes

P0250 P0251 P0252 P0253 P0254 P0255
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Code

P0256

GWM P — Powertrain

- Fuel Injector B Fuel Sensor Malfunction (Cam / Rotor / Injector)

Brand: GWM
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in the fuel metering control B wiring or connector
  • Corroded or loose connector at pump/solenoid
  • Faulty fuel metering solenoid, actuator, cam/rotor or meter assembly
  • Low fuel supply/pressure or clogged filter affecting pump response
  • ECM/PCM output driver failure
  • Intermittent wiring damage (chafing, pinched harness)

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Hard starting or extended cranking
  • Loss of engine power, poor acceleration
  • Rough idle or misfire under load
  • Reduced fuel economy
  • Intermittent engine stalling or limp-home mode

What to check

  • Retrieve freeze-frame and freeze data with a scan tool; confirm P0256 is active vs. historical
  • Inspect wiring and connector at injection pump B for corrosion, damage, pins pushed out or water intrusion
  • Check battery voltage and ground integrity at pump harness
  • Backprobe control connector and monitor signal while cranking/starting and at idle
  • Measure resistance of metering solenoid/actuator and compare to specification
  • Use a lab scope to view PWM duty cycle and waveform from ECM to solenoid

Signal parameters

  • Control signal type: PWM pulse-width modulated drive (ECM to solenoid/actuator)
  • Expected voltage range: approx. 0–12 V (varies by vehicle; when saturated ~battery voltage, when off ~0 V)
  • Typical duty cycle: 0–100% depending on commanded fuel metering (varies with engine load)
  • Typical frequency range: tens to a few hundred Hz (commonly 50–500 Hz)
  • Solenoid coil resistance: vehicle-specific — check service specification (often a few ohms to tens of ohms)

Diagnostic algorithm

  1. Use a scan tool to confirm P0256 and note freeze-frame parameters (engine speed, load, battery voltage, fuel pressure). Clear code and attempt to reproduce.
  2. Visually inspect connector and wiring to injection pump B. Repair or replace any damaged wiring or corroded terminals.
  3. With key on engine off (KOEO) and battery charged, measure voltage and ground at pump connector. Ensure stable battery voltage and good ground.
  4. Backprobe the control pin and monitor with a multimeter or scope while cranking and running. Verify presence of expected PWM signal and that duty cycle changes with throttle.
  5. Measure solenoid/actuator resistance. If open or shorted, replace solenoid/assembly.
  6. If electrical checks pass, check mechanical operation: verify fuel inlet pressure and that the pump/meters move freely (follow safe procedures; relieve fuel pressure before disconnecting).
  7. If intermittent, perform wiggle test of harness while monitoring live data to spot intermittent opens/shorts.
  8. If wiring and pump check good but signal is absent or incorrect, test ECM output driver. Swap with known-good circuit only if service manual allows, or bench-test ECM/driver per procedures.
  9. After repairs, clear codes and road-test to verify proper operation and that code does not return.

Likely causes

  • Broken or shorted control wire to metering solenoid B
  • Poor ground or battery voltage at pump control connector
  • Failed metering valve/solenoid on injection pump B
  • Fuel contamination causing sticking valve or rotor wear
  • Failed ECM driver for pump metering circuit B
  • Connector corrosion or water ingress at pump harness

Fault status

⚠️ Status
Injection Pump Fuel Metering Control B circuit or operation malfunction detected.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5 - 4.0 hours

Similar codes

P0250 P0251 P0252 P0253 P0254 P0255
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Code

P0256

HUMMER P — Powertrain

Injection Pump Fuel Metering Control "B" Malfunction (Cam/Rotor/Injector)

Brand: HUMMER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in the fuel metering control B wiring or connector
  • Corroded or loose connector at pump/solenoid
  • Faulty fuel metering solenoid, actuator, cam/rotor or meter assembly
  • Low fuel supply/pressure or clogged filter affecting pump response
  • ECM/PCM output driver failure
  • Intermittent wiring damage (chafing, pinched harness)

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Hard starting or extended cranking
  • Loss of engine power, poor acceleration
  • Rough idle or misfire under load
  • Reduced fuel economy
  • Intermittent engine stalling or limp-home mode

What to check

  • Retrieve freeze-frame and freeze data with a scan tool; confirm P0256 is active vs. historical
  • Inspect wiring and connector at injection pump B for corrosion, damage, pins pushed out or water intrusion
  • Check battery voltage and ground integrity at pump harness
  • Backprobe control connector and monitor signal while cranking/starting and at idle
  • Measure resistance of metering solenoid/actuator and compare to specification
  • Use a lab scope to view PWM duty cycle and waveform from ECM to solenoid

Signal parameters

  • Control signal type: PWM pulse-width modulated drive (ECM to solenoid/actuator)
  • Expected voltage range: approx. 0–12 V (varies by vehicle; when saturated ~battery voltage, when off ~0 V)
  • Typical duty cycle: 0–100% depending on commanded fuel metering (varies with engine load)
  • Typical frequency range: tens to a few hundred Hz (commonly 50–500 Hz)
  • Solenoid coil resistance: vehicle-specific — check service specification (often a few ohms to tens of ohms)

Diagnostic algorithm

  1. Use a scan tool to confirm P0256 and note freeze-frame parameters (engine speed, load, battery voltage, fuel pressure). Clear code and attempt to reproduce.
  2. Visually inspect connector and wiring to injection pump B. Repair or replace any damaged wiring or corroded terminals.
  3. With key on engine off (KOEO) and battery charged, measure voltage and ground at pump connector. Ensure stable battery voltage and good ground.
  4. Backprobe the control pin and monitor with a multimeter or scope while cranking and running. Verify presence of expected PWM signal and that duty cycle changes with throttle.
  5. Measure solenoid/actuator resistance. If open or shorted, replace solenoid/assembly.
  6. If electrical checks pass, check mechanical operation: verify fuel inlet pressure and that the pump/meters move freely (follow safe procedures; relieve fuel pressure before disconnecting).
  7. If intermittent, perform wiggle test of harness while monitoring live data to spot intermittent opens/shorts.
  8. If wiring and pump check good but signal is absent or incorrect, test ECM output driver. Swap with known-good circuit only if service manual allows, or bench-test ECM/driver per procedures.
  9. After repairs, clear codes and road-test to verify proper operation and that code does not return.

Likely causes

  • Broken or shorted control wire to metering solenoid B
  • Poor ground or battery voltage at pump control connector
  • Failed metering valve/solenoid on injection pump B
  • Fuel contamination causing sticking valve or rotor wear
  • Failed ECM driver for pump metering circuit B
  • Connector corrosion or water ingress at pump harness

Fault status

⚠️ Status
Injection Pump Fuel Metering Control B circuit or operation malfunction detected.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5 - 4.0 hours

Similar codes

P0250 P0251 P0252 P0253 P0254 P0255
Repair manuals

Manual library for HUMMER

138

Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

HUMMER

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+100 karma for a short comment :)
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Code

P0256

LAND ROVER P — Powertrain

Fuel measurement control of injection pump B

Brand: LAND ROVER
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Open or short in the fuel metering control B wiring or connector
  • Corroded or loose connector at pump/solenoid
  • Faulty fuel metering solenoid, actuator, cam/rotor or meter assembly
  • Low fuel supply/pressure or clogged filter affecting pump response
  • ECM/PCM output driver failure
  • Intermittent wiring damage (chafing, pinched harness)

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Hard starting or extended cranking
  • Loss of engine power, poor acceleration
  • Rough idle or misfire under load
  • Reduced fuel economy
  • Intermittent engine stalling or limp-home mode

What to check

  • Retrieve freeze-frame and freeze data with a scan tool; confirm P0256 is active vs. historical
  • Inspect wiring and connector at injection pump B for corrosion, damage, pins pushed out or water intrusion
  • Check battery voltage and ground integrity at pump harness
  • Backprobe control connector and monitor signal while cranking/starting and at idle
  • Measure resistance of metering solenoid/actuator and compare to specification
  • Use a lab scope to view PWM duty cycle and waveform from ECM to solenoid

Signal parameters

  • Control signal type: PWM pulse-width modulated drive (ECM to solenoid/actuator)
  • Expected voltage range: approx. 0–12 V (varies by vehicle; when saturated ~battery voltage, when off ~0 V)
  • Typical duty cycle: 0–100% depending on commanded fuel metering (varies with engine load)
  • Typical frequency range: tens to a few hundred Hz (commonly 50–500 Hz)
  • Solenoid coil resistance: vehicle-specific — check service specification (often a few ohms to tens of ohms)

Diagnostic algorithm

  1. Use a scan tool to confirm P0256 and note freeze-frame parameters (engine speed, load, battery voltage, fuel pressure). Clear code and attempt to reproduce.
  2. Visually inspect connector and wiring to injection pump B. Repair or replace any damaged wiring or corroded terminals.
  3. With key on engine off (KOEO) and battery charged, measure voltage and ground at pump connector. Ensure stable battery voltage and good ground.
  4. Backprobe the control pin and monitor with a multimeter or scope while cranking and running. Verify presence of expected PWM signal and that duty cycle changes with throttle.
  5. Measure solenoid/actuator resistance. If open or shorted, replace solenoid/assembly.
  6. If electrical checks pass, check mechanical operation: verify fuel inlet pressure and that the pump/meters move freely (follow safe procedures; relieve fuel pressure before disconnecting).
  7. If intermittent, perform wiggle test of harness while monitoring live data to spot intermittent opens/shorts.
  8. If wiring and pump check good but signal is absent or incorrect, test ECM output driver. Swap with known-good circuit only if service manual allows, or bench-test ECM/driver per procedures.
  9. After repairs, clear codes and road-test to verify proper operation and that code does not return.

Likely causes

  • Broken or shorted control wire to metering solenoid B
  • Poor ground or battery voltage at pump control connector
  • Failed metering valve/solenoid on injection pump B
  • Fuel contamination causing sticking valve or rotor wear
  • Failed ECM driver for pump metering circuit B
  • Connector corrosion or water ingress at pump harness

Fault status

⚠️ Status
Injection Pump Fuel Metering Control B circuit or operation malfunction detected.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5 - 4.0 hours

Similar codes

P0250 P0251 P0252 P0253 P0254 P0255
413

Browse 413 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

LAND ROVER

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+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
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