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

Circuit Description

The fuel tank pressure (FTP) sensor is a potentiometer. The alternative fuels engine control module (AF ECM) supplies about 5 volts on the FTP sensor reference voltage circuit. The AF ECM also supplies a ground circuit to the FTP sensor. When fuel level/tank pressure is full the FTP sensor signal voltage rises to 4.1 volts. As fuel level/tank pressure decreases to empty, the FTP sensor signal voltage drops to around 0.5 volts. The AF ECM monitors both the FTP sensor signal circuit voltage and the fuel tank temperature (FTT) sensor in order to determine the amount of fuel within the tank.

This DTC is used to indicate an FTP sensor signal voltage that is above the normal operating range of the sensor.

Conditions for Running the DTC

The engine is operating on alternative fuel.

Conditions for Setting the DTC

The AF ECM monitors an FTP sensor signal voltage of greater than 4.70 volts for at least 1 second continuously.

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

Conditions for Clearing the MIL/DTC
    • The Last Test Failed status will clear when the DTC runs and passes.
    • The History status will clear after FORTY consecutive WARM-UP cycles with NO failures of ANY DTC.
    • All DTC Information can be cleared using a scan tool.
    • Interruption of Control Module (AF ECM / 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 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 the 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 sensor and FTT sensor share a sensor ground, and open condition between the splice and the AF 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 the ignition ON leaving the engine OFF.
  2. Using a scan tool establish communication with the AF ECM.
  3. Locate and observe the Fuel Pressure sensor data parameter.

Does the Fuel Pressure sensor indicate voltage greater 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 Temperature sensor data parameter.

Does the Fuel Temperature sensor indicate voltage greater 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 Cover Replacement .
  2. Disconnect the fuel tank pressure (FTP) sensor connector.
  3. Connect a fused jumper between the FTP sensor signal circuit terminal and a known good ground.

    4. If the jumper fuse opens, repair the signal circuit shorted to battery voltage.

  4. Observe the Fuel Pressure sensor data parameter.

Does the Fuel Pressure sensor indicate 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 the J 39200 DMM between the 5-volt reference circuit terminal and the sensor ground circuit terminal.
  3. Measure the voltage of the 5-volt reference circuit.

Is the voltage GREATER than the specified value?

5.2 V

Go to Step 10

Go to Step 7

7

Connect the J 35616-200 12 - V Unpowered Test Lamp between the sensor ground circuit terminal and BATTERY POSITIVE.

Is the test lamp illuminated?

--

Go to Step 12

Go to Step 11

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

Was a repair necessary?

--

Go to Step 15

Go to Step 14

9
  1. Inspect the FTP sensor signal circuit for an open or high resistance condition between the AF ECM connector terminal and the circuit splice.
  2. Inspect the AF ECM connector and any in-line connectors, if applicable, for proper terminal contact.
  3. Inspect for a shorted condition between the FTP sensor 5-volt reference circuit and the FTP sensor signal circuit.
  4. Repair wiring or terminals as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 14

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

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

  2. Repair 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 sensor connector terminal and the circuit splice.

Is the repair complete?

--

Go to Step 15

--

12
  1. Inspect the FTP sensor connector for proper terminal contact.
  2. Repair terminal contact 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 AF ECM. Refer to Alternative Fuels Engine Control Module Replacement .
  2. Program - flash -- 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