GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC K Sierra - 4WD (CNG) 🢒 DTC 🢒 DTC P1432

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 fuel level/tank pressure is full the FTP signal voltage rises to 4.1 volts. As 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 sets when the FTP sensor signal voltage is below 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 Alternative Fuels ECM monitors an FTP signal voltage of less than 0.5 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.

Test Description

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

  1. This step determines if the condition is present.

    2.

  2. This step determines if the signal circuit of the FTP sensor is the cause of the condition.

    3.

  3. This step determines if the 5-volt reference circuit is the cause of the condition.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

1

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

--

Go to Step 2

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

2

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

Does the scan tool display the FTP sensor voltage less than the specified value?

0.5 V

Go to Step 4

Go to Step 3

3
  1. Observe the Freeze Frame and/or the Failure records data for this DTC.
  2. Turn the ignition OFF 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 and/or the Failure records data.
  5. Monitor the Alternative Fuels ECM DTC information with a scan tool.

Does the DTC fail this ignition cycle?

--

Go to Step 4

Go to Intermittent Conditions

4

  1. Remove the fuel tank cover. Refer to Fuel Tank Cover Replacement .
  2. Disconnect the harness connector of the FTP sensor.
  3. Observe the FTP sensor data parameter with a scan tool.

Does the scan tool display the FTP sensor voltage more than the specified value?

4.7 V

Go to Step 5

Go to Step 6

5

Measure the voltage from the 5-volt reference circuit of the FTP sensor with a DMM.

Is the voltage less than the specified value?

4.8 V

Go to Step 7

Go to Step 8

6

Test for a short to ground on the signal circuit of the FTP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

7

Test for an open or a short to ground on the 5 Volt reference circuit of the FTP sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

8

Inspect for proper terminal contact at the harness connector of the FTP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Inspect for proper terminal contact at the harness connector of the Alternative Fuels ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

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

Is the replacement complete?

--

Go to Step 12

--

11

Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs from the following control modules:
    2. • Alternative Fuels ECM
    • PCM
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 13

Go to Step 2

13

With a scan tool, select Capture Info in order to observe the stored information.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK