Circuit Description
The compressed natural gas (CNG) fuel tank pressure (FTP) sensor is a pressure transducer. The fuel injector control module (FICM) supplies about 5 volts on the FTP sensor reference voltage circuit. The FICM also supplies a signal circuit and a low reference 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 FICM communicates the FTP data to the powertrain control module (PCM) by a pulse width modulated (PWM) circuit. The PCM uses the FTP sensor and the fuel tank temperature (FTT) sensor in order to determine 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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1432 Fuel Pressure Sensor Circuit Low Voltage
Conditions for Running the DTC
| • | The ignition voltage is between 6-18 volts. |
| • | The engine is cranking or running. |
Conditions for Setting the DTC
| • | DTC P1207 is not set. |
| • | The FTP signal voltage is less than 0.1 volts. |
| • | The condition exists for at least 2 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module switches over to gasoline fuel operation. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if the condition is present.
-
This step determines if the signal circuit of the FTP sensor is the cause of the condition.
-
This step determines if the 5-volt reference circuit is the cause of the condition.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views | ||||
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) |
Does the scan tool display the FTP sensor voltage less than the specified value? | 0.1 V | Go to Step 4 | Go to Step 3 | |
3 |
Does the DTC fail this ignition cycle? | -- | Go to Step 4 | Go to Intermittent Conditions |
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 | |
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 fuel injector control module (FICM). 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 FTP sensor. Refer to Fuel Tank Pressure Sensor Replacement . Is the replacement complete? | -- | Go to Step 12 | -- |
11 | Replace the FICM. Refer to Fuel Injector Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 |
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
