GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Express (CNG) 🢒 Engine 🢒 Engine Controls - 6.0L 🢒 DTC P0183

Circuit Description

The fuel tank temperature (FTT) sensor is a variable resistor that measures the temperature of the fuel in the CNG fuel tank. The PCM supplies 5 volts to the FTT signal circuit. This DTC sets when the FTT signal voltage is above the normal operating range of the sensor.

Conditions for Running the DTC
    • The ignition is ON.
    • The intake air temperature is more than -35°C (-31°F).

Conditions for Setting the DTC
    •  The fuel tank temperature sensor voltage is more than 4.95 volt.
    • The condition exists for more than 5 seconds.

Action Taken When the DTC Sets
    • The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

Conditions for Clearing the DTC
    • A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
    • A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Use a scan tool in order to clear the DTC.

Diagnostic Aids
    • Use the Temperature vs Resistance table in order to test the FTT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in a driveability condition. If the engine has sat overnight, the FTT sensor and the intake air temperature values should display within a few degrees. If the temperatures are not within 3°C (5°F), refer to Fuel Temperature Sensor Output Voltage Versus Temperature Resistance .
    • For an intermittent condition, refer to Intermittent Conditions .

Test Description

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

  1. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

    2.

  2. This step tests the signal circuit of the FTT sensor for a short to another 5-volt reference circuit.

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?

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Go to Step 2

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

2
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the FTT sensor parameter with a scan tool.

Does the scan tool indicate that the FTT is near the specified value?

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 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 and/or the Failure records data.

Does the DTC fail this ignition cycle?

--

Go to Step 4

Go to Diagnostic Aids

4

  1. Turn OFF the ignition.
  2. Disconnect the FTT sensor. Refer to High Pressure Lock-Off Solenoid Replacement .

    3. Important: If the fuse opens, repair the short to voltage on the FTT signal circuit.

  3. Connect a 3-amp fused jumper wire between the signal circuit of the FTT sensor and the low reference circuit of the FTT sensor.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the FTT parameter with a scan tool.

Does the scan tool indicate that the FTT is at the specified value?

0 V

Go to Step 7

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the signal circuit of the FTT sensor and a good ground.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the FTT parameter with a scan tool.

Does the scan tool indicate that the FTT is at the specified value?

0 V

Go to Step 9

Go to Step 6

6

Test the signal circuit of the FTT sensor for an open circuit or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the G/H Van Service Manual.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 8

7

Test for an intermittent and for a poor connection at the FTT sensor. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the G/H Van Service Manual.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

8

Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the G/H Van Service Manual.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

9

Repair the low reference circuit of the FTT sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems in the G/H Van Service Manual.

Did you find and complete the repair?

--

Go to Step 12

--

10

Replace the FTT sensor. The FTT sensor is not serviceable separately from the HPL. Refer to High Pressure Lock-Off Solenoid Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls in the G/H Van Service Manual.

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Turn ON the ignition, with the engine OFF.
  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 13

13

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK