GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Savana (CNG) 🢒 DTC 🢒 DTC P1433

Circuit Description

The fuel tank pressure (FTP) sensor is a pressure transducer. The Alternative Fuels ECM supplies about 5 volts on the FTP sensor reference voltage circuit. The Alternative Fuels ECM also supplies a ground circuit to the FTP sensor. When the fuel level/tank pressure is full, the FTP signal voltage rises to 4.1 volts. As the fuel level/tank pressure decreases to empty, the FTP signal voltage drops to around 0.5 volts. The Alternative Fuels ECM monitors the FTP signal circuit voltage and the fuel tank temperature (FTT) sensor and determines the amount of fuel within the fuel tank.

This DTC is used to indicate a FTP sensor signal voltage that is greater than the normal operating range of the sensor.

Conditions for Running the DTC
    • The engine is operating on alternative fuel.
    • The fuel temperature is less than 30°C (86°F).

Conditions for Setting the DTC

The Alternative Fuels ECM monitors an FTP signal voltage of more than 4.70 volts for at least 1 second continuously.

Action Taken When the DTC Sets
    • The Alternative Fuels ECM will NOT illuminate the MIL.
    • The Alternative Fuels ECM will store this DTC as History during one drive trip in which the diagnostic runs and fails.
    • The Alternative Fuels ECM will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data.

Conditions for Clearing the DTC
    • The Last Test Failed status will clear when the DTC runs and passes.
    • The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC.
    • All DTC Information can be cleared using a scan tool.
    • Interruption of Control Module (Alternative Fuels ECM or the gasoline VCM / PCM or ECM) power or ground MAY clear DTC Information. Clearing DTC Information with this method is in-consistent and should not be performed.

Diagnostic Aids

Intermittent Condition

A fault not present indicates the condition that caused the DTC to set is intermittent and not currently present. Refer to the Intermittent Conditions diagnostic information located in Symptoms - Engine Controls. If any additional DTCs were stored proceed to the applicable DTC table in the order stated in Diagnostic System Check - Alternative Fuels (Engine Controls) .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step determines if the failure condition is present.

    2.

  2. This step determines if an open sensor ground circuit condition is present. Since the FTP and FTT share a sensor ground, an open condition between the splice and the Alternative Fuels ECM would cause both signal circuits to indicate high voltage.

    3.

  3. This step determines if an open or shorted signal circuit is the cause of the failure condition.

    4.

  4. This step determines if a shorted 5-volt reference circuit is the cause of the failure condition.

    5.

  5. This step determines if an open sensor ground circuit between the FTP connector and the circuit splice is the cause of the failure condition.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Alternative Fuels Engine Controls Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2

  1. Turn ON the ignition, with the engine OFF.
  2. Using a scan tool, establish communication with the Alternative Fuels ECM.
  3. Locate and observe the Fuel Tank Pressure (FTP) sensor data parameter.

Is the FTP voltage more than the specified value?

4.7 V

Go to Step 4

Go to Step 3

3

The fault is not present. Refer to Diagnostic Aids.

Are any DTCs stored that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Intermittent Conditions

4

Locate and observe the fuel tank temperature (FTT) sensor data parameter.

Is the FTT voltage more than the specified value?

4.7 V

Go to Step 8

Go to Step 5

5

  1. Remove the fuel tank cover. Refer to Fuel Tank Shield Replacement .
  2. Disconnect the FPS connector.
  3. Connect a fused jumper between the FTP signal circuit terminal and a known good ground.

    4. Important: If the jumper fuse opens, repair the signal circuit short to battery voltage.

  4. Observe the fuel tank pressure (FTP) sensor data parameter.

Is the FTP voltage less than the specified value?

0.25 V

Go to Step 6

Go to Step 9

6

  1. Remove the jumper.
  2. Connect the test leads of a digital multimeter (DMM) between the 5-volt reference circuit terminal and a known good ground.
  3. Measure the voltage of the 5-volt reference circuit.

Is the voltage more than the specified value?

5.2 V

Go to Step 10

Go to Step 7

7

Connect the J 35616-200 Unpowered Test Lamp between the sensor ground circuit terminal and B+.

Does the test lamp illuminate?

--

Go to Step 12

Go to Step 11

8
  1. Inspect the sensor ground circuit for an open or a high resistance condition between the Alternative Fuels ECM connector terminal and the circuit splice.
  2. Inspect the Alternative Fuels ECM connector and any in-line connectors, if applicable, for proper terminal contact.
  3. Repair the wiring or terminals as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 14

9
  1. Inspect the FTP signal circuit for an open or a high resistance condition between the Alternative Fuels ECM connector terminal and the circuit splice.
  2. Inspect the Alternative Fuels ECM connector and any in-line connectors, if applicable, for proper terminal contact.
  3. Repair the wiring or terminals as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 14

10
  1. Inspect the FTP 5-volt reference circuit for a short to voltage.

    2. The FTP 5-volt reference circuit is NOT shared with any other 5-volt reference component on the vehicle.

  2. Repair the wiring as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 14

11

Repair the open or high resistance condition of the sensor ground circuit between the FTP connector terminal and the circuit splice.

Is the repair complete?

--

Go to Step 15

--

12
  1. Inspect the FTP connector for proper terminal contact.
  2. Inspect for a shorted condition between the FTP 5-volt reference circuit and the FTP signal circuit.
  3. Repair the terminal contact or wiring as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 13

13

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

Is the replacement complete?

--

Go to Step 15

--

14
  1. Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .
  2. Program the replacement Control Module with the correct vehicle software and calibration.

Is the replacement complete?

--

Go to Step 15

--

15
  1. Using a scan tool, clear the DTC information from both Control modules.
  2. Operate the vehicle under the Conditions for Running the DTC.
  3. Using the scan tool parameter DTC Status, ensure that this DTC runs.

Did this DTC run and pass?

--

System OK

Go to Step 2