GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 GMC T-Series Medium Duty Truck F6/F7/F8 🢒 DTC 🢒 DTC P0193

Circuit Description

The fuel rail pressure sensor is installed to the fuel rail. The fuel rail pressure detects the fuel pressure in the fuel rail, converts the pressure into a voltage signal, and sends the signal to the engine control module (ECM). The fuel rail pressure sensor has the following circuits:

   • 

A 5-volt reference circuit

   • 

A low reference circuit

   • 

A fuel rail pressure sensor signal circuit

The ECM supplies 5 volts to the fuel rail pressure sensor on the 5-volt reference circuit. The ECM also provides a ground on the low circuit. Higher fuel rail pressure provides higher fuel pressure sensor voltage, while lower pressure provides lower fuel pressure sensor voltage. The ECM calculates the actual fuel rail pressure, fuel pressure, from the voltage signal, and uses the result in fuel injection control and other control tasks. The ECM monitors the fuel rail pressure sensor signal for voltage outside the normal range. If the ECM detects an excessively high fuel rail pressure sensor signal voltage, this DTC will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0193 Fuel Rail Pressure (FRP) Sensor Circuit High Voltage

Conditions for Running the DTC
    • The ignition switch is ON.
    • The battery voltage is between 10-16 volts.

Conditions for Setting the DTC

The ECM detects that the fuel rail pressure sensor signal voltage is more than 4.7 volts.

Action Taken When the DTC Sets
    • The ECM illuminates the malfunction indicator lamp (MIL) and Reduced Engine Power indicator lamp, if fitted, when the diagnostic runs and fails.
    • The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
    • The ECM limits the fuel injection quantity for fail-safe operation.
    • The ECM limits the desired fuel rail pressure for fail-safe operation.
    • The ECM closes the exhaust gas recirculation (EGR) valve and holds the EGR valve to a closed position.
    • The ECM inhibits cruise control.

Condition for Clearing the DTC
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
    • If an intermittent condition is suspected, the following may cause an intermittent:
       - Poor connections
       - A misrouted harness
       - Rubbed through wire insulation
       - Broken wire inside the insulation
    • Inspect for the following conditions:
       - Poor connection at ECM--Inspect the harness connectors for the following conditions:
   • Backed-out terminals
   • Improper mating
   • Broken locks
   • Improperly formed or damaged terminals
   • Poor terminal to wire connection
       - Damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, observe the Engine Coolant Temperature display on the scan tool while moving the connectors and the wiring harness related to the sensor. A change in the display will indicate the location of the fault.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Observe the failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 3

Go to Diagnostic Aids

3
  1. Start the engine.
  2. Monitor the DTC Information with a scan tool.

Is DTC P0641 also set?

--

Go to DTC P0641

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Disconnect the fuel pressure sensor connector.
  3. Connect a DMM between the 5-volt reference circuit and the low reference circuit of the fuel pressure sensor.
  4. Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified range?

4.5-5.5 V

Go to Step 6

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Disconnect the fuel rail pressure sensor connector.
  3. Connect a DMM between the 5-volt reference circuit and a known good ground.
  4. Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified range?

4.5-5.5 V

Go to Step 10

Go to Step 9

6
  1. Turn OFF the ignition.
  2. Disconnect the fuel pressure sensor connector.
  3. Connect a DMM between the signal circuit and the low reference circuit of the fuel pressure sensor.
  4. Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified range?

4.5-5.5 V

Go to Step 7

Go to Step 8

7

Important: The fuel pressure sensor may be damaged if the circuit is shorted to a voltage source.

  1. Test the signal circuit between the engine control module (ECM) and the fuel pressure sensor for a short to ground circuit.
  2. Repair the circuit, as necessary.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

8
  1. Test the signal circuit between the ECM and the fuel pressure sensor for the following conditions:
    2. • An open circuit
    • High resistance
  2. Repair the circuit, as necessary.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

9
  1. Test the 5-volt reference circuit between the ECM and the fuel pressure sensor for the following conditions:
    2. • An open circuit
    • High resistance
  2. Repair the circuits, as necessary.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

10
  1. Test the low reference circuit between the ECM and the fuel pressure sensor for the following conditions:
    2. • An open circuit
    • High resistance
  2. Repair the circuits, as necessary.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

11
  1. Turn OFF the ignition.
  2. Disconnect the fuel pressure sensor connector.
  3. Inspect for poor connections at the harness connector of the fuel pressure sensor.
  4. Repair the connections, as necessary.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

12
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Inspect for poor connections at the harness connector of the ECM.
  4. Repair the connections, as necessary.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

13

Replace the fuel pressure sensor.

Did you complete the replacement?

--

Go to Step 15

--

14

Important: The new ECM must be programmed.

Replace the ECM. Refer to, Engine Control Module Replacement/Restore Fuel Rate Data , and Fuel Injector Flow Rate Programming .

Did you complete the replacement?

--

Go to Step 15

--

15
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 16

16

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK