Code
P0629
Generic
P — Powertrain
Fuel Pump A Control Circuit High
Views:
UK: 27
EN: 47
RU: 38
AI status
Completed
Completed
100%
Causes
- Short to battery voltage on the fuel pump A control circuit
- Stuck or welded fuel pump relay contacts
- Faulty fuel pump module (internal electronics) feeding the control circuit
- Corroded, damaged or disconnected wiring or connector
- Failed PCM/ECM driver transistor or internal short
- Aftermarket wiring or accessories tied into the fuel pump circuit
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Fuel pump may run continuously or fail to be commanded off
- Hard start, no start or intermittent stalling
- Parasitic battery drain when vehicle is off
- Reduced or erratic fuel pressure/delivery
- Possible buzzing/relay chatter at relay box
What to check
- Confirm DTC P0629 and note freeze-frame/conditions
- Visual inspection of fuel pump relay, fuse, connectors and wiring for damage or corrosion
- Check for aftermarket splices or bypass wiring to pump
- Measure battery voltage and check for parasitic draw with key off
- Backprobe the fuel pump control circuit at the relay and at the PCM connector
- Swap relay with identical known-good relay (if applicable) and re-check
Signal parameters
- Typical: control is a low-side switch (PCM grounds the relay coil). When commanded ON: control pin ~0–1 V (grounded). When OFF: control pin floats/high (near battery through relay coil).
- Fault condition: control voltage higher than expected when PCM commands low (example: > ~5 V or near battery voltage while commanded ON).
- For modules with PWM control: expected duty 0–100% at manufacturer-specific frequency (often tens to hundreds of Hz); waveform should switch between near 0 V and near battery.
- Nominal battery voltage: ~12.0–14.5 V with engine running — compare measured values to this.
Diagnostic algorithm
- Verify the code with a scanner and record freeze-frame data and ignition/state when the fault set.
- Visually inspect harnesses, relay box, pump module connector and ground points for corrosion, melted insulation, or aftermarket taps.
- With key ON (engine off), backprobe the PCM pump-control pin and measure voltage while commanding the pump (some tools can request/activate the pump). Observe whether the PCM attempts to pull the circuit low.
- If control circuit reads high when PCM should be pulling it low, isolate whether the high is coming from the relay or the pump module: unplug the fuel pump connector or relay coil circuit and re-test the control pin.
- If unplugging the pump/relay makes the control voltage return to expected values, inspect/replace the pump module or repair wiring to the module. If the control remains high with loads disconnected, suspect a relay short to +B or PCM fault.
- Swap the fuel pump relay with an identical known-good relay (if accessible) and retest to rule out a stuck relay.
- Perform continuity and short-to-battery checks on the control wire between the PCM, relay and pump module. Repair any shorted/short-to-B wires or poor connector terminals.
- Use a lab scope to check waveform under commanded ON: confirm PWM characteristics if applicable and look for battery feedback or irregular switching.
- Only after all wiring, relay and pump module checks fail should the PCM be considered for replacement — confirm PCM driver failure with bench or manufacturer procedures.
- After repairs, clear codes, verify no reoccurrence and perform a functional test (operate pump, check fuel pressure, verify key-off current draw).
Likely causes
- Short to constant battery +B on control wire (most common)
- Relay contacts stuck closed or relay coil wiring shorted
- Damaged connector (pin pushed out, corrosion) at pump module or relay
- Failed pump module with internal driver feeding back voltage
- PCM output stage failure (less common)
Fault status
Status
PCM detected abnormally high voltage on Fuel Pump A control circuit. Possible short to battery, stuck relay, defective pump module or PCM driver fault. Circuit requires wiring/relay/pump/PCM investigation.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email
Code
P0629
HUMMER
P — Powertrain
Fuel Pump Relay Control Circuit High Voltage
Views:
UK: 17
EN: 32
RU: 22
AI status
Completed
Completed
100%
Causes
- Short to battery voltage on the fuel pump A control circuit
- Stuck or welded fuel pump relay contacts
- Faulty fuel pump module (internal electronics) feeding the control circuit
- Corroded, damaged or disconnected wiring or connector
- Failed PCM/ECM driver transistor or internal short
- Aftermarket wiring or accessories tied into the fuel pump circuit
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Fuel pump may run continuously or fail to be commanded off
- Hard start, no start or intermittent stalling
- Parasitic battery drain when vehicle is off
- Reduced or erratic fuel pressure/delivery
- Possible buzzing/relay chatter at relay box
What to check
- Confirm DTC P0629 and note freeze-frame/conditions
- Visual inspection of fuel pump relay, fuse, connectors and wiring for damage or corrosion
- Check for aftermarket splices or bypass wiring to pump
- Measure battery voltage and check for parasitic draw with key off
- Backprobe the fuel pump control circuit at the relay and at the PCM connector
- Swap relay with identical known-good relay (if applicable) and re-check
Signal parameters
- Typical: control is a low-side switch (PCM grounds the relay coil). When commanded ON: control pin ~0–1 V (grounded). When OFF: control pin floats/high (near battery through relay coil).
- Fault condition: control voltage higher than expected when PCM commands low (example: > ~5 V or near battery voltage while commanded ON).
- For modules with PWM control: expected duty 0–100% at manufacturer-specific frequency (often tens to hundreds of Hz); waveform should switch between near 0 V and near battery.
- Nominal battery voltage: ~12.0–14.5 V with engine running — compare measured values to this.
Diagnostic algorithm
- Verify the code with a scanner and record freeze-frame data and ignition/state when the fault set.
- Visually inspect harnesses, relay box, pump module connector and ground points for corrosion, melted insulation, or aftermarket taps.
- With key ON (engine off), backprobe the PCM pump-control pin and measure voltage while commanding the pump (some tools can request/activate the pump). Observe whether the PCM attempts to pull the circuit low.
- If control circuit reads high when PCM should be pulling it low, isolate whether the high is coming from the relay or the pump module: unplug the fuel pump connector or relay coil circuit and re-test the control pin.
- If unplugging the pump/relay makes the control voltage return to expected values, inspect/replace the pump module or repair wiring to the module. If the control remains high with loads disconnected, suspect a relay short to +B or PCM fault.
- Swap the fuel pump relay with an identical known-good relay (if accessible) and retest to rule out a stuck relay.
- Perform continuity and short-to-battery checks on the control wire between the PCM, relay and pump module. Repair any shorted/short-to-B wires or poor connector terminals.
- Use a lab scope to check waveform under commanded ON: confirm PWM characteristics if applicable and look for battery feedback or irregular switching.
- Only after all wiring, relay and pump module checks fail should the PCM be considered for replacement — confirm PCM driver failure with bench or manufacturer procedures.
- After repairs, clear codes, verify no reoccurrence and perform a functional test (operate pump, check fuel pressure, verify key-off current draw).
Likely causes
- Short to constant battery +B on control wire (most common)
- Relay contacts stuck closed or relay coil wiring shorted
- Damaged connector (pin pushed out, corrosion) at pump module or relay
- Failed pump module with internal driver feeding back voltage
- PCM output stage failure (less common)
Fault status
Status
PCM detected abnormally high voltage on Fuel Pump A control circuit. Possible short to battery, stuck relay, defective pump module or PCM driver fault. Circuit requires wiring/relay/pump/PCM investigation.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
HTML Workshop Manuals AI manual library for HUMMER Click to show available manuals 77
HUMMER 2010 H3 Alpha
HTML ManualHUMMER 2010 H3 Base, Standard
HTML ManualHUMMER 2010 H3 Base, Automatic
HTML ManualHUMMER 2010 H3T Alpha
HTML ManualHUMMER 2010 H3T Base, Standard
HTML ManualHUMMER 2010 H3T Base, Automatic
HTML ManualHUMMER 2009 H2 4D Utility Wagon
HTML ManualHUMMER 2009 H2 4D Utility Pickup
HTML ManualYour experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email
Code
P0629
LAND ROVER
P — Powertrain
Fuel Pump A Control - High Circuit
Views:
UK: 18
EN: 29
RU: 17
AI status
Completed
Completed
100%
Causes
- Short to battery voltage on the fuel pump A control circuit
- Stuck or welded fuel pump relay contacts
- Faulty fuel pump module (internal electronics) feeding the control circuit
- Corroded, damaged or disconnected wiring or connector
- Failed PCM/ECM driver transistor or internal short
- Aftermarket wiring or accessories tied into the fuel pump circuit
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Fuel pump may run continuously or fail to be commanded off
- Hard start, no start or intermittent stalling
- Parasitic battery drain when vehicle is off
- Reduced or erratic fuel pressure/delivery
- Possible buzzing/relay chatter at relay box
What to check
- Confirm DTC P0629 and note freeze-frame/conditions
- Visual inspection of fuel pump relay, fuse, connectors and wiring for damage or corrosion
- Check for aftermarket splices or bypass wiring to pump
- Measure battery voltage and check for parasitic draw with key off
- Backprobe the fuel pump control circuit at the relay and at the PCM connector
- Swap relay with identical known-good relay (if applicable) and re-check
Signal parameters
- Typical: control is a low-side switch (PCM grounds the relay coil). When commanded ON: control pin ~0–1 V (grounded). When OFF: control pin floats/high (near battery through relay coil).
- Fault condition: control voltage higher than expected when PCM commands low (example: > ~5 V or near battery voltage while commanded ON).
- For modules with PWM control: expected duty 0–100% at manufacturer-specific frequency (often tens to hundreds of Hz); waveform should switch between near 0 V and near battery.
- Nominal battery voltage: ~12.0–14.5 V with engine running — compare measured values to this.
Diagnostic algorithm
- Verify the code with a scanner and record freeze-frame data and ignition/state when the fault set.
- Visually inspect harnesses, relay box, pump module connector and ground points for corrosion, melted insulation, or aftermarket taps.
- With key ON (engine off), backprobe the PCM pump-control pin and measure voltage while commanding the pump (some tools can request/activate the pump). Observe whether the PCM attempts to pull the circuit low.
- If control circuit reads high when PCM should be pulling it low, isolate whether the high is coming from the relay or the pump module: unplug the fuel pump connector or relay coil circuit and re-test the control pin.
- If unplugging the pump/relay makes the control voltage return to expected values, inspect/replace the pump module or repair wiring to the module. If the control remains high with loads disconnected, suspect a relay short to +B or PCM fault.
- Swap the fuel pump relay with an identical known-good relay (if accessible) and retest to rule out a stuck relay.
- Perform continuity and short-to-battery checks on the control wire between the PCM, relay and pump module. Repair any shorted/short-to-B wires or poor connector terminals.
- Use a lab scope to check waveform under commanded ON: confirm PWM characteristics if applicable and look for battery feedback or irregular switching.
- Only after all wiring, relay and pump module checks fail should the PCM be considered for replacement — confirm PCM driver failure with bench or manufacturer procedures.
- After repairs, clear codes, verify no reoccurrence and perform a functional test (operate pump, check fuel pressure, verify key-off current draw).
Likely causes
- Short to constant battery +B on control wire (most common)
- Relay contacts stuck closed or relay coil wiring shorted
- Damaged connector (pin pushed out, corrosion) at pump module or relay
- Failed pump module with internal driver feeding back voltage
- PCM output stage failure (less common)
Fault status
Status
PCM detected abnormally high voltage on Fuel Pump A control circuit. Possible short to battery, stuck relay, defective pump module or PCM driver fault. Circuit requires wiring/relay/pump/PCM investigation.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email
Code
P0629
MITSUBISHI
P — Powertrain
Suction control valve high
Views:
UK: 16
EN: 26
RU: 26
AI status
Completed
Completed
100%
Causes
- Short to battery voltage on the fuel pump A control circuit
- Stuck or welded fuel pump relay contacts
- Faulty fuel pump module (internal electronics) feeding the control circuit
- Corroded, damaged or disconnected wiring or connector
- Failed PCM/ECM driver transistor or internal short
- Aftermarket wiring or accessories tied into the fuel pump circuit
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Fuel pump may run continuously or fail to be commanded off
- Hard start, no start or intermittent stalling
- Parasitic battery drain when vehicle is off
- Reduced or erratic fuel pressure/delivery
- Possible buzzing/relay chatter at relay box
What to check
- Confirm DTC P0629 and note freeze-frame/conditions
- Visual inspection of fuel pump relay, fuse, connectors and wiring for damage or corrosion
- Check for aftermarket splices or bypass wiring to pump
- Measure battery voltage and check for parasitic draw with key off
- Backprobe the fuel pump control circuit at the relay and at the PCM connector
- Swap relay with identical known-good relay (if applicable) and re-check
Signal parameters
- Typical: control is a low-side switch (PCM grounds the relay coil). When commanded ON: control pin ~0–1 V (grounded). When OFF: control pin floats/high (near battery through relay coil).
- Fault condition: control voltage higher than expected when PCM commands low (example: > ~5 V or near battery voltage while commanded ON).
- For modules with PWM control: expected duty 0–100% at manufacturer-specific frequency (often tens to hundreds of Hz); waveform should switch between near 0 V and near battery.
- Nominal battery voltage: ~12.0–14.5 V with engine running — compare measured values to this.
Diagnostic algorithm
- Verify the code with a scanner and record freeze-frame data and ignition/state when the fault set.
- Visually inspect harnesses, relay box, pump module connector and ground points for corrosion, melted insulation, or aftermarket taps.
- With key ON (engine off), backprobe the PCM pump-control pin and measure voltage while commanding the pump (some tools can request/activate the pump). Observe whether the PCM attempts to pull the circuit low.
- If control circuit reads high when PCM should be pulling it low, isolate whether the high is coming from the relay or the pump module: unplug the fuel pump connector or relay coil circuit and re-test the control pin.
- If unplugging the pump/relay makes the control voltage return to expected values, inspect/replace the pump module or repair wiring to the module. If the control remains high with loads disconnected, suspect a relay short to +B or PCM fault.
- Swap the fuel pump relay with an identical known-good relay (if accessible) and retest to rule out a stuck relay.
- Perform continuity and short-to-battery checks on the control wire between the PCM, relay and pump module. Repair any shorted/short-to-B wires or poor connector terminals.
- Use a lab scope to check waveform under commanded ON: confirm PWM characteristics if applicable and look for battery feedback or irregular switching.
- Only after all wiring, relay and pump module checks fail should the PCM be considered for replacement — confirm PCM driver failure with bench or manufacturer procedures.
- After repairs, clear codes, verify no reoccurrence and perform a functional test (operate pump, check fuel pressure, verify key-off current draw).
Likely causes
- Short to constant battery +B on control wire (most common)
- Relay contacts stuck closed or relay coil wiring shorted
- Damaged connector (pin pushed out, corrosion) at pump module or relay
- Failed pump module with internal driver feeding back voltage
- PCM output stage failure (less common)
Fault status
Status
PCM detected abnormally high voltage on Fuel Pump A control circuit. Possible short to battery, stuck relay, defective pump module or PCM driver fault. Circuit requires wiring/relay/pump/PCM investigation.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email