Fix P0627: Mechanic’s solutions that WORKED

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The P0627 code indicates a malfunction in the fuel pump control circuit. This fault can arise from various issues, such as a defective fuel pump relay, wiring problems, or PCM malfunctions. It primarily affects the vehicle’s ability to effectively control the fuel pump, which is crucial for engine operation.

P0627 quick overview

Meaning	P0627: Fuel Pump “A” Control Circuit/Open
Is it serious?	This code can be serious as it affects the fuel system, potentially leading to engine stalling or a no-start condition.
Possible causes	– Faulty fuel pump relay or control circuit – Issues with the Powertrain Control Module (PCM) – Damaged wiring or poor connections in the fuel pump circuit – Faulty or failing fuel pump – Problems with the Totally Integrated Power Module (TIPM)
How to diagnose?	Inspect Fuel Pump Relay: Check the fuel pump relay for proper operation and signs of damage. Examine Wiring and Connections: Look for damaged wiring or loose connections, especially between the PCM and TIPM. Check PCM Functionality: Ensure the PCM is functioning correctly and providing appropriate signals. Diagnose TIPM Issues: Investigate potential issues with the TIPM, which may affect fuel pump operation. Test Fuel Pump Operation: Verify if the fuel pump is operating properly when commanded. Utilize Diagnostic Tools: Use scan tools to read PCM data and perform active tests on the fuel pump.

How to fix P0627 – learn from mechanics

I looked into P0627 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Honda

Vehicle Information: 2015 Honda Accord EX-L 3.5L Long crank time

Issue + Repair History: Intermittent long crank time. Suspected fuel pressure regulator issue. Previous repair included fuel pump relay replacement.

Computer Codes & Descriptions: P0627 – Fuel Pump Control (FPC) System Malfunction

Other Test Results: Fuel pressure at idle: 50-60 psi

Suggestions to Fix Issue:

• Check for correct fuel pressure (57 to 64 psi).
• Consider the possibility of a leaking injector or a check valve issue in the fuel pump.
• Inspect wiring, injection module, and fuel pump for potential faults.
• Follow a diagnostic flow chart to address the P0627 code.
• Apply the “20/20” rule: system should maintain 20 psi for 20 minutes after engine shut off.

Final Fix: The problem was resolved by replacing the in-tank fuel pump assembly. Post-replacement, the fuel pressure remained at 50 psi even 15 minutes after turning off the vehicle, indicating a faulty fuel pressure regulator/check valve.

Case #2: Cadillac

Vehicle Information: 2006 Cadillac CTS 3.6L MIL Lamp on

Issue + Repair History:

• Trouble turning ignition lock cylinder to lock position.
• Traction control and security lights on.
• Codes p0627, p1629, u1000, u1300 present.
• Replaced ECM which fixed the ignition lock cylinder issue, but codes returned.
• Door locks cycle on their own intermittently when engine is running.

Computer Codes & Descriptions:

• P0627 – Fuel Pump Relay Control Circuit
• P1629 – Theft Deterrent Fuel Enable Not Received
• U1000 – Class 2 Data Malfunction
• U1300 – Class 2 Data Link Low

Suggestions to Fix Issue:

• Check if reflashing the ECM helps.
• Inspect PRNDL switch voltages during malfunction.
• Examine communication between BCM and PCM; check class two serial data circuits.
• Investigate serial data wiring between ECM and EBCM; ensure scanner can connect with EBCM or SDM.
• Confirm if the ECM is programmed and set up correctly.

Final Fix: The root cause was identified as a bad connection on the main engine ground on the block (lower right side). This was discovered during a wiggle-test on the wiring harnesses and monitoring the “active/inactive” status of the modules. Fixing the ground connection resolved the issue.

Case #3: Dodge

Vehicle Information: 2007 Dodge Ram 1500 ST 5.7L No Start

Issue + Repair History:

• No fuel pump operation.
• Initial code P127E (Fuel Pump Control Circuit) led to TIPM replacement.
• Replaced TIPM and fuel pump but still no start; new code P0627.
• Replaced PCM, but issue persisted.
• Able to start the vehicle by jumping fuel pump at TIPM.
• Problem traced to a lack of signal from PCM to TIPM.
• All parts were OEM and programmed.

Computer Codes & Descriptions:

• P0627 – Fuel Pump Control Circuit

Suggestions to Fix Issue:

• Verify if new components (TIPM, PCM) are functioning correctly.
• Check if PCM grounds the brown wire (pin 37 connector 3) to command TIPM to power up fuel pump.
• Use a bi-directional scan tool to activate the fuel pump and diagnose the issue.
• Consider the possibility of a new faulty part.
• Confirm if the front control module came with the new TIPM.
• Ensure the new ECM is programmed to operate the fuel pump through the TIPM.
• Check for the need to re-wire the TIPM for older systems.

Final Fix: The issue was resolved by locating and repairing a broken brown wire at connector C1, close to the terminal. This fix restored proper communication and operation, resolving the no-start issue.

Case #4: Jeep

Vehicle Information: 2008 Jeep Wrangler Unlimited Rubicon 3.8L No Start

Issue + Repair History:

• Cranks but does not start, towed in for service.
• Many no communication codes present, with P0627 listed first.
• No power on the fuel pump fuse.
• Discrepancy in TIPM connector color coding; confusion over which connector to use.
• PCM not grounding the fuel pump relay; engine runs when manually grounded.
• Owner reported engine had run low on oil multiple times.

Computer Codes & Descriptions:

• P0627 – Fuel Pump Control

Suggestions to Fix Issue:

• Match wire location and color from diagrams to the correct connector.
• Identify correct TIPM connector using marks (A to F) and check for ground on pin 40.
• Test CAN network for issues, monitor CAN high and low voltages, and verify termination resistors.
• Check all powers and grounds to TIPM, focusing on the brown wire (C1 pin 40).
• Consider checking modules such as TPMS or sway bar disconnect for network issues.
• Investigate the possibility of a faulty TIPM; consider an external relay kit for rewiring if necessary.

Final Fix: The problem was traced to the PCM not grounding the fuel pump relay. Upon manually providing the ground, the engine ran. The vehicle was eventually towed back to the owner’s house to address the no-start and other issues, as the owner needed to assess his budget for repairs.

Case #5: Dodge

Vehicle Information: 2004 Dodge Ram 1500 ST 4.7L Engine Won’t Shut Off

Issue + Repair History:

• Engine keeps running for a few seconds to minutes after turning key off.
• Dash goes blank when the key is off.
• Set codes P0627 and P0645.
• Replaced ignition switch; issue resolved temporarily but then returned.
• Able to control fuel and A/C relays with a scanner.
• Engine runs and then starts loping until it dies due to fuel pump relay having no power with the key off.
• Suspected issue with PCM, confirmed by testing.

Computer Codes & Descriptions:

• P0627 – Fuel Pump Relay Circuit
• P0645 – A/C Relay Circuit

Suggestions to Fix Issue:

• Check for any aftermarket installations like remote starts, amplifiers, or stereo systems.
• Inspect for shorts to power, especially in aftermarket installations.
• Pull relevant relays (fuel pump, A/C, ASD) when the engine won’t shut off to check for backfeed.
• Verify actuation of the Auto Shut Down (ASD) relay and check if it’s physically sticking.
• Examine the electric fan for potential backfeed into the system.
• Disconnect the alternator to rule out A/C ripple interference with PCM.
• Check the cooling fan’s operation and fan control module for a bad diode.

Final Fix: The issue was traced to a small amount of voltage keeping the PCM awake. A broken pin (pin 11) on the PCM was found to have 1.5 volts with the key off. The problem was intermittent, making it difficult to diagnose initially. A temporary fix involved attaching a 20-ohm resistor to pin 11 to ground, pulling the bleed to ground and allowing the truck to shut off consistently. The customer decided to use this temporary fix while considering further action.

Advice	Brief Description of Diagnostic Step
Check PCM and TIPM Connections	Inspect for proper grounding and voltage at the PCM (Powertrain Control Module) and TIPM (Totally Integrated Power Module) connections.
Verify Wiring Integrity	Ensure there are no broken wires or bad connections, especially between the PCM and TIPM.
Inspect Fuel Pump Relay	Check the fuel pump relay circuit for proper operation and possible backfeed issues.
Consider Impact of Aftermarket Installations	Evaluate any aftermarket components (like remote starts, amplifiers, or stereo systems) for potential interference or incorrect wiring.
Test for Short Circuits or Backfeed	Look for any short circuits or backfeed in the system that could keep the PCM active or affect relay operation.
Perform Diagnostic Flow Chart Steps	Follow the diagnostic steps outlined in the vehicle’s service manual or diagnostic flow chart specific to the P0627 code.
Use Bi-Directional Scan Tools	Utilize bi-directional scan tools to activate components like fuel pumps to aid in diagnostics.
Monitor Voltage and Ground Signals	Regularly check voltage and ground signals in key areas such as the fuel pump relay circuit and PCM connector pins.