Det 1

My truck has a persistent problem of a sudden, but momentary, loss of power. After reading the sticky thread about the shorted wire I thought that was the underlying issue. But I have carefully looked over the entire lower portion of that loom and found no cracks or bare spots in the wires. None the less, I retaped each wire and put plastic loom over them. The problem remains.

Codes P0587 and P0514 are showing on the odometer window after turning the ignition key to on three times.

I've considered that my OEM lift pump could be having issues. 129k on the odometer and the truck still runs really strong, though the mileage seems to be decreasing (14-17 mpg unloaded).

It seems that [U]nearly[U] everytime the loss of power happens the temp guage has gone a little over 200 degrees and the motor cuts out just as the fan kicks in. Maybe it's coincidental, but it sure appears that's what happens.

I'm considering ordering an OEM lift pump from Geno's. I can't justify, nor afford right now, the in-tank option, nor a frame mounted pump.

Any and all suggestions are welcome. Thanks.

BigIron70

P0587-LOW VOLTAGE DETECTED AT THE SPEED CONTROL VENT
DRIVER
P0514-BAT TEMPERATURE SENSOR RATIONALITY
Neither of these codes would cause lack of power.
I would recomend doing TSB 18-022-07 which is an update to ECM software
The following enhancements are included with this software:
1. Improved engine cooling (radiator fan activation) and prevention of possible engine
overheat. When coolant temperature faults are present the radiator fan is enabled
(turned on) during vehicle operation.
2. Correction to oil pressure reading when engine is operating at higher engine
temperatures above 91°C (195°F).
3. Improvement to the Temperature Sensor Rationality Test to prevent possible false test
failures and the following related Diagnostic Trouble Codes (DTC's):
a. DTC P0071 - Inlet Air Temperature Sensor Rationality.
b. DTC P0111 - Intake Air Temperature (IAT) Sensor Rationality.
c. DTC P0514 - Battery Temperature Sensor Rationality.
4. Additional Water-In-Fuel (WIF) warning added to indicate that the operator has had a
WIF DTC P2269 and has continued to operate (drive) the vehicle in excess of 500
miles without draining the water from the fuel filter. The following is the new WIF DTC
that has been added:
a. DTC P0169 - WIF Too Long Error
Usually lift pump code P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP would indicate a lift pump going out. Because of your mileage 129K it might be wise to replace it anyway or at lease do a flow test. Min 560 mL in
10 seconds or better is expected for model year 2003 and early 2004 vehicles
I would also check battery connections and grounds since the ECM grounds at the drivers side battery. Any corrosion or loose connections there will cause you problems.
P0587 could be a cruise control servo. More diag. might be necessary. Possible servo will need DRB to test circuit.
Turn the ignition off.
Disconnect the Speed control servo harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Ignition on, engine not running.
With the DRBIIIt, actuate the Speed Control Vent Solenoid.
Using a 12-volt test light connected to battery positive, check the Speed Control Vent
Solenoid Output circuit in the Speed Control Assembly harness connector.
NOTE: The test light must illuminate brightly. Compare the brightness to
that of a direct connection to the battery.
Does the test light cycle on and off and illuminate brightly?
All
Yes ! Replace the speed control servo assembly.
Good Luck

Det 1

Thanks for the reply and suggestions. I'll start looking into them and hope that one of them is a cure.