24v

I've got eratic oil pressure (sometimes doesn't register on gauge), WIF light on, check engine light on and a P1488 code. Now last night, it starting surging....kinda like half-power, full-power, half-power, full-power...again eratically.

I know the P1488 code is auxillary 5volt supply outlet too low.....but I don't know what that means, or how to fix it.

Any ideas???????

vzdude

The 5v supply, goes to all the sensors. If one of them is shorted to ground, it will cause some really goofy stuf like what your having! here:

Symptom:
P-1488 AUXILIARY 5 VOLT OUTPUT TOO LOW
POSSIBLE CAUSES
NO POSSIBLE CAUSES
5-VOLT SUPPLY CIRCUIT OPEN
5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
MAP SENSOR WIRING HARNESS INTERMITTENT DEFECT
MAP SENSOR WIRING HARNESS OBSERVABLE DEFECT
CAMSHAFT POSITION SENSOR DEFECTIVE
ENGINE CONTROL MODULE DEFECTIVE
MANIFOLD AIR PRESSURE SENSOR DEFECTIVE
OIL PRESSURE SENSOR DEFECTIVE
WATER IN FUEL SENSOR DEFECTIVE

TEST ACTION APPLICABILITY
1133 Ignition On, Engine Not Running.
With the DRB, read DTC’s.
Is the DTC Specific Good Trip displayed and equal to 0?
ENGINE- 5.9L
DIESEL
Yes ® Go To 1134
No ® Go To 1141
1134 Ignition Off
Disconnect the MAP Sensor Electrical Connector.
Note: Check connectors - Clean/repair as necessary.
Ignition On, Engine Not Running
Using a voltmeter, measure the 5-Volt Supply Circuit to MAP Sensor.
Is the voltage above 4.5 volts?
ENGINE- 5.9L
DIESEL
Yes ® Replace the MAP Sensor.
Perform Powertrain Verification Test VER-2A
No ® Go To 1135
1135 Ignition Off
Disconnect the MAP Sensor Electrical Connector.
Note: Check connectors - Clean/repair as necessary.
Ignition On, Engine Not Running
Using a voltmeter, measure the 5-Volt Supply Circuit to MAP Sensor.
Disconnect the CMP Sensor Electrical Connector.
Note: Check connectors - Clean/repair as necessary.
Did the voltage change to above 4.5 volts?
ENGINE- 5.9L
DIESEL
Yes ® Replace The CMP Sensor.
Perform Powertrain Verification Test VER-2A
No ® Go To 1136
1136 Ignition Off
Disconnect the MAP Sensor Electrical Connector.
Note: Check connectors - Clean/repair as necessary.
Ignition On, Engine Not Running
Using a voltmeter, measure the 5-Volt Supply Circuit to MAP Sensor.
Disconnect the Oil Pressure Snesor Electrical Connector.
Note: Check connectors - Clean/repair as necessary.
Did the voltage change to above 4.5 volts?
ENGINE- 5.9L
DIESEL
Yes ® Replace the Oil Pressure Sensor.
Perform Powertrain Verification Test VER-2A
No ® Go To 1137
1137 Ignition Off
Disconnect the MAP Sensor Electrical Connector.
Note: Check connectors - Clean/repair as necessary.
Ignition On, Engine Not Running
Using a voltmeter, measure the 5-Volt Supply Circuit to MAP Sensor.
Disconnect the Water In Fuel Sensor Electrical Connector.
Note: Check connectors - Clean/repair as necessary.
Did the voltage change to above 4.5 volts?
ENGINE- 5.9L
DIESEL
Yes ® Replace the Water In Fuel Sensor.
Perform Powertrain Verification Test VER-2A
No ® Go To 1138
459
DRIVEABILITY
P-1488 AUXILIARY 5 VOLT OUTPUT TOO LOW — Continued1138 Ignition Off
Disconnect the MAP Sensor Electrical Connector.
Disconnect the Engine Control Module.
Note: Check connectors - Clean/repair as necessary.
Using an ohmmeter, measure the resistance of the 5-Volt Supply Circuit to ground.
Is the resistance below 5.0 ohms?
ENGINE- 5.9L
DIESEL
Yes ® Repair the 5-Volt Supply Circuit for a short to ground.
Perform Powertrain Verification Test VER-2A
No ® Go To 1139
1139 Ignition Off
Disconnect the MAP Sensor Electrical Connector.
Disconnect the Engine Control Module.
Note: Check connectors - Clean/repair as necessary.
Using an ohmmeter, measure the resistance of the 5-Volt Supply (CMP) Circuit, MAP
to ECM.
Is the resistance below 5.0 ohms?
ENGINE- 5.9L
DIESEL
Yes ® Go To 1140
No ® Repair the open 5-Volt Supply Circuit.
Perform Powertrain Verification Test VER-2A
1140 If there are no potential causes remaining, the Engine Control Module is assumed to
be defective.
View repair options.
ENGINE- 5.9L
DIESEL
Repair
Replace the Engine Control Module.
Perform Powertrain Verification Test VER-2A
1141 Ignition On, Engine Not Running.
With the DRB, read the MAP Sensor voltage.
Wiggle the MAP Sensor Connector & Harness.
Monitor the DRB display.
Was there any MAP Sensor voltage change?
ENGINE- 5.9L
DIESEL
Yes ® Repair the Harness or Connector that caused the voltage change.
Perform Powertrain Verification Test VER-2A.
No ® Go To 1142
1142 Ignition Off
Using the schematic as a guide, inspect the Wiring and Connectors.
Were any problems found?
ENGINE- 5.9L
DIESEL
Yes ® Repair as necessary.
Perform Powertrain Verification Test VER-2A.
No ® Go To 1143
460
DRIVEABILITY
P-1488 AUXILIARY 5 VOLT OUTPUT TOO LOW — ContinuedTEST ACTION APPLICABILITY
1143 Visually inspect relatedWire Harness Connectors. Look for broken, bent, pushed out,
or corroded Terminals.
Visually inspect the related Harnesses. Look for chafed, pierced, or partially broken
Wires.
Refer to any hotlines or technical service bulletins that may apply.
If there are no other possible causes remaining there is assumed to be an 9intermittent9
problem with a Wiring Harness Connector or Wire.
View repair options.
ENGINE- 5.9L
DIESEL
Repair
Test complete.
461
DRIVEABILITY
P-1488 AUXILIARY 5 VOLT OUTPUT TOO LOW — Continued