I have an 03 slt with the 5.9. If anyone saw my last thread, she's a difficult old girl. After resolving my old problems and removing my automatic starter, I've found a new problem. Under the hood in the fuse/relay box, one of the small 20 amp fuses (labeled as ignsw) keeps blowing. I've replaced it three times, and although it's labeled as an ignition switch, my D will start fine with it blown. Today I pulled codes to find P0442(small emissions leak, old problem and unrelated) and a new one- P0627, which if I'm correct is a shorted or open circuit fuel pump. This makes no sense though... My D starts and runs fine. Any other reasons why this code would be thrown or how to fix it? There's been no recent maintenance or other issues, other than the fuse blowing for ignsw. Thanks guys!

 

That code will also show up if there is a poor electrical connection to the fuel pump as well

 

Symptom:
P0627-FUEL PUMP RELAY CIRCUIT
When Monitored and Set Condition:
P0627-FUEL PUMP RELAY CIRCUIT
When Monitored: With the ignition on. Battery voltage greater than 10.4 volts.
Set Condition: An open or shorted condition is detected in the fuel pump relay control
circuit.
POSSIBLE CAUSES
FUEL PUMP RELAY OPERATION
(F18) FUSED IGNITION SWITCH OUTPUT CIRCUIT
FUEL PUMP RELAY
(K31) FUEL PUMP RELAY CONTROL CIRCUIT OPEN
(K31) FUEL PUMP RELAY CONTROL CIRCUIT SHORTED TO GROUND
PCM
TEST ACTION APPLICABILITY
1 Ignition on, engine not running.
With the DRBIIIt, actuate the Fuel Pump Relay.
Is the Fuel Pump Relay operating?
All
Yes ! Refer to the INTERMITTENT CONDITION Symptom (Diagnostic
Procedure).
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No ! Go To 2
2 Turn the ignition off.
Remove the Fuel Pump Relay from the PDC.
Ignition on, engine not running.
Using a 12-volt test light connected to ground, probe the (F18) Fused Ignition Switch
Output circuit in the PDC.
Does the test light illuminate brightly?
All
Yes ! Go To 3
No ! Repair the (F18) Fused Ignition Switch Output circuit. Inspect
the related fuse. An open fuse may have been caused by a short to
ground.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
3 Turn the ignition off.
Measure the resistance of the Fuel Pump Relay Coil.
Is the resistance between 70 to 90 ohms?
All
Yes ! Go To 4
No ! Replace the Fuel Pump Relay.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
434
DRIVEABILITY - NGC


TEST ACTION APPLICABILITY
4 Disconnect the PCM harness connectors.
CAUTION: DO NOT PROBE THE PCM HARNESS CONNECTORS. PROBING
THE PCM HARNESS CONNECTORS WILL DAMAGE THE PCM TERMINALS
RESULTING IN POOR TERMINAL TO PIN CONNECTION. INSTALL
MILLER SPECIAL TOOL #8815 TO PERFORM DIAGNOSIS.
Measure the resistance of the (K31) Fuel Pump Relay Control circuit from the PDC
to the appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
All
Yes ! Go To 5
No ! Repair the open in the (K31) Fuel Pump Relay Control circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
5 Measure the resistance between ground and the (K31) Fuel Pump Relay Control
circuit in the PDC.
Is the resistance below 5.0 ohms?
All
Yes ! Repair the short to ground in the (K31) Fuel Pump Relay Control
circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
No ! Go To 6
6 NOTE: Before continuing, check the PCM harness connector terminals for
corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay
particular attention to all Power and Ground circuits.
If there are no possible causes remaining, view repair.
All
Repair
Replace and program the Powertrain Control Module per Service
Information.

This the test procedures we use at the dealership.