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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC C Pickup - 2WD (CNG) 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 DTC 66 Fuel Pressure Sensor Circuit Low Voltage

Object Number: 327058 Size: SF
Handling Electrostatic Discharge Sensitive Parts Notice
Handling Electrostatic Discharge Sensitive Parts Notice
CNG Fuel Controls
Engine Controls Components
OBDII Symbol Description Notice

Circuit Description

The fuel pressure sensor (FPS) supplies the ECU a variable voltage signal from 0.5 volts to 4.5 volts that changes relative to fuel pressure. The FPS voltage varies from about 0.5 volts at 0 kPa (0 psi) to 4.1 volts at 24 820 kPa (3,600 psi). This is a type C DTC.

Conditions for Setting the DTC

The following conditions will set the DTC:

    • The ignition is ON.
    • The FPS voltage is greater than 4.7 volts.

Action Taken When the DTC Sets

The ECU will set DTC 67 after two consecutive driving trips with the fault active.

Conditions for Clearing the MIL/DTC

The DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°C (72°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during that same ignition cycle) or the code clearing procedure has been used.

Diagnostic Aids

When a DTC 67 sets, a short to power in the FPS circuit is indicated. Always inspect any circuitry that is suspected of causing an intermittent complaint for the following conditions:

    • Backed out terminals
    • Improper mating
    • Broken locks
    • Improperly formed or damaged terminals
    • Poor terminal-to-wire connection
    • Damaged harness

Important: When the fuel gauge selector switch is depressed, the gauge will display the dormant fuel level for 10 seconds and then return to normal operation

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step verifies that the fault is present.

    2.

  2. This step inspects the sensor reference voltage.

    3.

  3. This step inspects the sensor ground circuit.

DTC 66 -- Fuel Pressure Sensor Circuit High Voltage (1998 Only)

Step

Action

Value(s)

Yes

No

1

Was the Alternative Fuels (AF) Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Alternative Fuels (AF) Powertrain On Board (OBD) System Check

2

  1. Start the engine.
  2. Allow the engine to idle for 15 seconds.
  3. Turn the ignition OFF for ten seconds.
  4. Start the engine.
  5. Allow the engine to idle for 15 seconds.
  6. Turn the ignition OFF.
  7. Retrieve codes from the AF ECU.

Was DTC 67 retrieved?

--

Go to Step 3

Go to Intermittent Conditions

3

  1. Disconnect the fuel pressure sensor (FPS) connector C315.
  2. Turn ON the ignition.
  3. Inspect for voltage at cavity B of C315 using a DVOM.

Is the voltage greater than the specified value?

5.2 V

Go to Step 6

Go to Step 4

4

Inspect for voltage at cavity C of connector C315 using a DVOM.

Is the voltage less than the specified value?

1.0 V

Go to Step 5

Go to Step 7

5

  1. Turn OFF the ignition.
  2. Inspect cavity A of connector C315 for continuity to ground using a DVOM.

Is there continuity?

--

Go to Step 8

Go to Step 11

6
  1. Turn the ignition OFF.
  2. Disconnect CLR ECU connector C003.
  3. Turn ON the ignition.
  4. Inspect for voltage at cavity B of connector C315.

Is the voltage greater than the specified value?

0.0 V

Go to Step 11

Go to Step 9

7
  1. Turn the ignition OFF.
  2. Disconnect BLU ECU connector C001.
  3. Turn ON the ignition.
  4. Inspect for voltage at cavity C of connector C315.

Is the voltage greater than the specified value?

0.0 V

Go to Step 11

Go to Step 9

8

Replace the fuel pressure sensor. Refer to Fuel Pressure Sensor Replacement .

Is the action complete?

--

Go to Step 12

--

9
  1. Inspect the ECU connector for damaged wiring or pins.
  2. Inspect connector C315 for damaged wiring or pins.

Is a problem found?

--

Go to Step 11

Go to Step 10

10

Replace the Engine Control Unit (ECU). Refer to Engine Control Unit Replacement .

Is the action complete?

--

Go to Step 12

--

11

Repair the circuit as necessary. Refer to Repair Procedures in Electrical Diagnosis in the 1998 C/K Truck Service Manual.

Is the action complete?

--

Go to Step 12

--

12
  1. Start the engine.
  2. Allow the engine to idle for 15 seconds.
  3. Turn the ignition OFF for 10 seconds.
  4. Start the engine and allow it to reach operating temperature.
  5. Turn the ignition OFF.
  6. Verify that no other DTCs are displayed.

Are any DTCs displayed that have not been diagnosed?

--

Go to the applicable DTC table.

System OK